UNIT I

PLANT PROPAGATION

Plant Propagation Defined

Plant propagation is the multiplication of plants by sexual and asexual means. The increase in number
and perpetuation of the species by reproduction.

Factors to Consider In Successful Plant Propagation

1. Environmental factors like temperature, relative humidity, and rainfall;

2. Technical skills. This can be attained from constant practice on how to bud or graft, how to make
cuttings, how to perform tissue culture (micro-propagation) or germinate seeds;
3. Knowledge of different kinds of crops and the various possible methods by which certain crop plants
can be reproduced.

Types Of Plant Propagation

A. Seed Propagation

Seed propagation is sometimes termed as sexual propagation. Papaya and coconut are mainly propagated
by seeds.

Advantages

Seed propagation offers a very good opportunity to produce new hybrids or varieties. Seed propagation
is an easy and cheap method of multiplying plants.

Disadvantages

For fruits and plantation crops, it takes time to flower and bear fruits for the first time (longer juvenile
period) and fruits tend to grow taller. It does not retain the characteristics of the mother plant.

Kinds of true botanical seeds. (1) Orthodox seeds - Seeds of some plants that could be kept viable for
longer periods, provided they are dried properly.
(2) Recalcitrant seeds - Seeds of plants that could not be kept for a long time. They cannot withstand drying and
should not be permitted to dry out before planting.

B. Vegetative (Asexual) Propagation

Vegetative propagation- involves the use of vegetative parts of the plant like the root, stem, and leaf to
increase the number of plants of the same kind. It is also called asexual propagation, since no union of the male
and female gametes is involved.

Advantages
1. The resulting plant posseses characteristics as the mother plant.
2. Used in plants where seed propagation is impossible or difficult.
3. The trees are usually smaller and bear fruits earlier than those grown from seeds.

B.1 Conventional vegetative method of propagation (natural vegetative propagation)

 a. Separation- is propagation using naturally detachable organs such as corms and bulbs (whole
plantlets). It also applies to the process of separating a clump into several portions, each with a root system.

Specialized organs used for propagation by separation.

Runners- a stem that grows horizontally along the ground. Example: strawberry.

Slips-leafy shoots originating from auxiliary buds borne at the base of a plant or fruit such as in cabbage and
pineapple.

Suckers-a new or secondary shoot that grows up beside the old plant. Example: pineapple, banana,
anthurium

Crown- a shoot formed on top of a fruit, like pineapple.

Bulb- is composed of shortened branches that later develop with thickened petioles. Example :onion

Bulblets- small bulbs produced at the base of the mother plant. Example: multiplier onion

Bulbils-aerial plantlets formed on the axil of the leaves or flower stalk. Example: Agave

Plantlets or Offset-a short lateral branch which develops from the crown and terminates into a rosette of leaves;
bulblets grown to full size. Example: dendrobium, phalaenopsis.

b. Division- is a method of asexual propagation wherein specialized or modified stems and roots are cut
into pieces or sections with at least one bud or eye per section. The structures used for propagation by separation
section of the following are used for division; corm, tuber, rhizome corms of abaca and banana that are cut are
variously referred as bits, seed bits or seed pieces.

Corms- is stem structure containing nodes and internodes and a few rudimentary leaves. Example: abaca, banana,
gabi or taro, gladiolus

Cormels- small corms

Tuber- an enlarged underground stem serving as storage organ of starch or related materials. Example: potato

Tuberous roots- Ex: sweet potato

Rhizome-a horizontal stem that grows at or below the surface of the ground. Ex: banana.

B.2 Artificial vegetative propagation

a. Cuttage- or use of cuttings is the method of artificial vegetative propagation involving regeneration of a
several plant part from the parent plant.

Types of cuttings

a) Leaf cuttings

a.1
leaf cuttings of plants with parallel veins Ex: Sanseviera sp. (snake/sword plant)
a.2leaf cuttings with thick fleshy leaves Example: begonia
a.3leaf cuttings from the entire leaf, the leaf blade only Example: Peperomia sp.
a.4Leaf cuttings from species bearing foliar embryos on the serrations of their leaf margins Example:
kalanchoe and cactus.
b) Leaf bud cuttings- This type of cuttings consist of leaf blade, petiole and short piece of the stem with
axillary bud Example: black pepper, sampaguita.

c) Stem cuttings- type of cuttings which are commonly used.

 c.1 hardwood cuttings- from mature wood from few year old stem Example: poinsettia, bougainvilla,
grape, sineguelas
c.2 semi-hardwood cuttings- cuttings from partially mature wood, with or without terminals.
Example: gumamela, rose, poinsettia, bougainvilla, grapes citrus
c.3 herbaceous stem cutting. This type is treated like softwood cutting. Example: cucharita

Requirement to have success rooting a) proper temperature (not higher than 27˚C b) a very humid
atmosphere (85-100% RH) c) ample light d) moist, clean, well aerated and well drained rooting medium, e)
oxygen

b. Grafting- is the process of joining together a rootstock and a scion until they unite permanently. The
rootstock or is the plant, usually a seedling, in which the scion is inserted. The scion is any plant part, usually a
stem, taken from the desired plant. When the scion part is only a small piece of bark containing a single bud, the
operation is termed budding or budgrafting

Requirements for successful grafting

1. compatible stock and scion

2. intimate contact of cambial regions of stock and scion
3. active stock and dormant scion
4. sharp grafting knife

Methods of grafting

1. cleft grafting 4. side grafting

2. saddle grafting 5. approach grafting or inarching
3. splice grafting

Methods of budding

1. shield budding or T budding 3. chip budding

2. inverted T budding 4. patch budding

c. Layering- a method of vegetative propagation wherein plants are allowed to regenerate other parts
while still attached to the parent plant.

Marcotting- the process of inducing the branch or twig to produce roots while still attached to the parent
plant. It is also called air layering.

B.3 Micropropagation

One of the latest approaches to plant propagation is a method called micro propagation (also called tissue
culture or meristem culture). This is an asexual method using sterilized terminal shoots or leaf buds placed on a
sterilized (disease –free) agar jell or other nutrient growing media. One part bleach to 10 parts media is used for
sterilizing, and the proper growth-regulating chemicals and nutrients are mixed in the growing media. The tips
and media are placed inside a test tube or small jar and kept sealed to keep out mold and disease organisms.

New tiny plant sprout out from the plant tissue placed in the sealed container. As the tiny sprouts grow
large enough to be moved, they are pulled off with sterile tweezers and placed in a new media in another container
to grow roots, or they may be used to grow more shoots. This process is repeated again and again as new sprouts
appear. As soon as roots develop, the container may be opened, a little more each day for about a week, allowing
the plants to harden off. Plants may then be transplanted to small containers and treated in the same manner as
small seedling transplant.
It is very important that all containers, growing media, hands etc. be sterile so that no plant disease
organisms are present. Thousands of new plants produced are exactly like the parents in short period. It is
estimated that in 28 weeks, one blackberry tip could produce 2.5 million tissue particles ready for rooting. Tissue
culture has been use for years on orchids.
C. Apomictic (Asexual)

Apomixis or apomictic seeds- seed development without the benefit of sexual fusion of the egg and the
sperm cells. The resulting plants are of the same characteristics as the mother plant. Apomictic seeds maybe
poly and monoembyonic seeds, examples: mangosteen, citrus, mango.

References

Books

Bautista, O. K. et al. 1994. Introduction to Tropical Horticulture. SEAMEO SEARCA,UPLB. College, Laguna.

Denisen, E.L. 1979. Principles of Horticulture. Macmillan Publishing Co., Inc,.NY,USA.

Halfacre, R.G. and J.A. Barden. 1979. Horticulture. McGraw-Hill book Co. Inc. USA

Hartman, H.T. and D.E. Kester. 1961. Plant Propagation: Principles and Practices. Prentice Hall, Inc. New Jersey.

Hartman, H., et.al. 1990. Plant Propagation: Principles and Practices. 5 th Edition. Prentice Hall International,
Inc. USA.

Reily, H.E. and C.L.Shry, Jr. 1991. Introductory Horticulture. 4rth Edition. Delmars Publishers Inc., USA
.
Taylor, J.L. 1977. Growing Plants Indoor. Burgess Publishing Co. Minneapolis, Minnesota.

Internet

Http://www.aggie-horticulture.tamu.edu/propagation/propgation.html-2k-13-May2004

Http://www.cesncsu -edu/depts/hort/hil/hil8702.html-31k-14May2004

Http://www.nmastergardeners.org/manual%20etc/other%20reference/propagation.htm
 UNIT II

LAND PREPARATION

By

Justo G. Canare Jr.

Land preparation is one of the many ways by which the farmer manipulates the environment to make it more
favorable for a crop. Its fundamental purpose is to provide a favorable soil environment for the germination
and/or growth of a particular crop. Although there are other operations under land preparation, the above-
mentioned purpose is mainly attained by tillage.

Definition of Terms

Land Preparation - the process of preparing the land for planting, thereby providing good physical,
chemical, and biological conditions that would permit optimum plant growth.

Tillage - the mechanical manipulation of the soil from a known condition to a different desired condition.
The desired conditions brought about by tillage are normally physical, but chemical and biological processes in
the soil are also affected.

Soil tilth - the physical condition of the soil as related to its ease of tillage, fitness as a seedbed, and its
impedance to seedling emergence and root penetration. It includes such soil conditions as adequate aeration,
sufficient moisture, ready infiltration of rainfall, and certain phases of consistency such as mellow and friable
characteristics.

General Steps in Preparing a Virgin Land

The first step in preparing a virgin land for crop production is clearing it to remove existing vegetation,
either completely or partially depending on the production system to be adopted (mechanized or nonmechanized)
and the crop to be produced.

Where production is not mechanized, as in developing countries, the bush is usually cleared and burned.
Some trees may be left standing intact or cut down to the trunk.

Where production is mechanized, as in developed countries, trees are not only cut down, but stumps are
also removed. All obstructions (e.g. roots and rocks) in the land that can interfere with the operation of tillage
implements are also removed.

If necessary, terrain modification may be done. This may involve the following:

1. Leveling. The land may require leveling to improve surface drainage, for installation of irrigation
equipment, or to facilitate the use of farm machines and equipment. In leveling, the fertile topsoil must be
conserved.

2. Terracing. Cropping steep slopes exposes the soil to rapid deterioration from soil erosion. In
mountainous production areas and places where undulating relief exists, the land may be terraced.

An irrigation system and a drainage system may also be established.

Finally, the land is ready to be prepared for seeding.

General Classes of Tillage Operations

Tillage operations may be divided into primary and secondary tillage.

 Primary tillage - this operation does the initial cutting or breaking of the soil at its state where either a
crop has been grown and harvested or simply a barren soil. It includes hoeing, spading, plowing and subsoiling.

In primary tillage, the topsoil is stirred to a depth of 15 centimeters or more and inverted, burying the
vegetation and debris on the soil surface. The soil surface is rough after the operation and unsuited for most
seeding operations.

Secondary tillage - operations on the soil after primary tillage. It includes breaking of the soil clods or
granulation (as in dryland preparation) or puddling (as in wetland preparation), thorough mixing of plant materials
into the soil, and leveling the field. Among the equipment used are the harrows.

In certain cultural systems, crops are planted in rows and on beds or ridges. In such cases, furrowing or
listing is included in secondary tillage.

Tillage Systems

Tillage systems refer to the nature and sequence of tillage operations used in preparing land for planting
a crop. Tillage systems differ in the degree of soil stirring and nature of the finished product. They may be
classified according to the degree of soil stirring into two basic groups: conventional tillage and conservation
tillage.

1. Conventional tillage. The entire field is stirred up to a certain depth (called the plow depth). This
requires using various kinds of implements. The final condition depends on the purpose of tillage and the crop to
be produced. Conventional tillage incorporates two basic methods: clean tillage (in which no debris or plant
residues are left on the soil surface), or mulch tillage (in which some debris is left on the soil surface).

Conventional tillage consists of three general steps:

a. The land is first cleared to remove large pieces of debris, trees and shrubs. This is necessary to facilitate the
use of tillage implements that are prone to damage from these obstacles, or are impeded in efficiency by such
materials. Low-growing grasses can be readily plowed under without the need for a pre-plowing clearing
operation.

b. Primary tillage implements are then used to bury the remaining plant materials on the soil surface.

c. The conventional tillage operations are completed by conducting a secondary tillage of the soil using lighter
implements.

The advantages of conventional tillage include the following:

a. Even though tillage may cause compaction, it is the most convenient method of managing soil compaction
when it occurs.

b. It is easier to apply fertilizers and perform other agronomic operations when the land is clean.

c. The lack of crop residue on the surface reduces the possibility of pests and diseases.

The disadvantages of conventional tillage are the following:

a. Erosion. The soil is left clean and exposed to agents of soil erosion.

b. Compaction. Several trips are required by the machinery or animals over the land during the tillage operations,
thus predisposing the soil to compaction. Repeated use of primary tillage implements at the same depth places
pressure on the soil in that region, resulting in compaction, creating a plow pan. Pan formation means the
producer may have to periodically conduct a deep plow tillage operation to dislodge or break down these
obstructions in the soil.
c. Cost. Conventional tillage is expensive, requiring different implements and several energy-consuming passes
over the field to complete the job.

d. Loss of soil organic matter. Soil organic matter decreases over time because of faster decomposition.

2. Conservation Tillage. This entails practices in which soil disturbance is reduced and some crop
residues remain on the soil surface after the operation. The chief goals of this tillage system are to reduce erosion
and conserve moisture. There are various types of conservation tillage practices that vary in the degree of soil
disturbance and the amount of crop residue on the soil surface. They are sometimes called crop residue
management systems and are more widely used in developed countries.

These types of tillage systems are not always distinct from each other. They may overlap in certain ways.
The methods of managing crop residues are variable among the types of conservation tillage.

The common types of conservation tillage include no tillage, mulch tillage, strip tillage, ridge tillage, and
minimum tillage.

a. No tillage (also called zero tillage and no till) describes a practice in which a crop is seeded directly into soil
that is not tilled since the harvest of the previous crop. Soil disturbance is limited only to the spot where the
seed would be placed. Weeds are controlled by herbicides prior to seeding. In onion, the soil is mulched, with
or without the application of herbicide.

b. Mulch tillage systems vary, but the common objective is to leave crop residue to serve as mulch. A variety of
implements are used to incorporate a part of the crop residue into the soil, the remainder left on top. One type
of mulch tillage is stubble-mulch tillage, in which the goals are to conserve moisture and protect the soil from
wind and water erosion by leaving crop residue on the soil surface.

c. Strip tillage (also called strip-till or zone tillage) entails the disturbance of narrow strips in the soil where
seeding is done. The interrow zone remains undisturbed and covered with crop residue.

d. Ridge tillage involves tilling a small band of soil on the ridge. The soil from the top of the ridge is mixed with
crop residue between ridges. The debris reduces erosion and also increases water retention.

e. Minimum tillage (also called reduced tillage) may involve considerable soil disturbance, though to a much
lesser extent than that associated with conventional tillage, or little soil disturbance. Some crop residue is left
on the soil surface. It refers to methods resulting in reduced tillage intensity or reduced number and type of
tillage operations. It includes methods that combine several operations into a one-pass operation like the so-
called plow-plant method, which combines land preparation and planting in one pass. The practice of simply
opening up the furrows where seeds can be sown is considered minimum tillage in the Philippines.

Conservation tillage has the following advantages:

a. Reduces soil erosion from wind and water. Crop residue impedes soil surface movements, trapping loose soil
and slowing down runoff.

b. Reduces soil compaction. Reduced use of tillage machinery reduces soil compaction. Further, the cover
provided by crop residue reduces compaction from rain and sprinkler irrigation.

c. Applicable to steep slopes. Because the soil is least disturbed and the surface protected, steep slopes can be
safely tilled with minimal consequence.

d. Soil infiltration and moisture conservation is high because of a large amount of crop residue. Surface residue
reduces evaporation and increases infiltration, thus maintaining higher soil moisture content.

e. Reduces cost of tillage. Conventional tillage involves several passes with farm machinery, and thus is more
costly in terms of fuel use.

f. Soil temperature moderation. Crop residue has an insulating effect on the soil. It shades the topsoil and reduces
temperature fluctuation in this layer. Temperature reduction is advantageous in summer when sunlight is
 intense. However, during the cold months, the temperature-reducing effect makes soils under conservation
tillage cooler, slowing down seed germination.

g. Soil organic matter is known to increase over prolonged periods of no tillage.

Conservation tillage has the following disadvantages:

a. Dependence on chemicals. Drastically reduced soil stirring means chemicals are depended upon in no-till
operations for weed control.

b. Cost. In mechanized farming, the equipment used for seeding under conventional tillage cannot be used in
untilled soil. Special mechanical planters are required for no-till seeding, increasing the cost. (However, in
non-mechanized farms, no tillage and minimum tillage reduce cost of land preparation.)

c. Higher risk of insect pests and pathogens in early crop establishment because of soil-borne pathogens and
soil surface insects. The high moisture stability favors the survival of soil pathogens, such as Rhizoctonia and
Phythium. Further, insects, rodents, grubs, and other pests thrive on the crop residue. (However, other pests
are also reduced by the presence of crop residues, particularly rice stubbles, on the surface.)

d. Crop residues impede the application of fertilizers.

e. High levels of herbicide use increase the opportunities for the development of herbicide resistance and the
possibility of harmful effects on human health and the environment.

Methods of Land Preparation

Dryland or upland preparation - tillage is performed at relatively low moisture content, well below the
saturation moisture level. The soil is loosened and granulated to promote plant growth. The resulting condition
is such that water and air may move more freely through it.

Wetland or lowland preparation - the soil is tilled when it is saturated with water.

F. Specific Objectives of Tilling Flooded Soils (Wetland Preparation)

1. to control weeds
2. to mix organic materials with the soil
3. to incorporate fertilizers and soil amendments to the soil
4. to turn soil into soft puddle for ease in transplanting
5. to form a hard layer (plow sole) which reduces water and leaching losses during the subsequent
flooding stages

G. Specific Objectives Of Tilling Upland Soils (Dryland Preparation)

1. to control weeds
2. to mix organic materials with the soil
3. to incorporate fertilizers and soil amendments to the soil
4. to develop proper soil tilth (desirable soil structure)
5. to improve soil aeration

H. Land Preparation Practices

1. Conventional method of preparing upland soils (dryland preparation)

 In general, the method consists of plowing to break and loosen the soil, followed by harrowing to
further loosen the soil and break the soil clods into smaller particles, to thoroughly incorporate plant
materials into the soil and to level the field.

Frequency of tillage operations. There is no clear-cut recommendation on the number of plowings

and harrowings required. The number depends on the type of crop, type of soil, and amount of plant
materials in the field. Care, however, must be exercised not to over-pulverize the soil so that in the event
of rain and subsequent drying, the formation of hard and compact surface soil layer, or crust, could be
avoided. This crust can prevent the emergence of seedlings, reduce aeration and water infiltration, increase
surface run-off, and increase erosion.

Timing of tillage operations. The moisture content of the soil dictates the timing of tillage. Tilling
the soil when it is too wet destroys the structure of the soil. Tilling when it is too dry does not promote
good granulation and may cause breakage of implements. The correct moisture content for tilling the soil
is at a level slightly below field capacity. Because of the inconvenience of determining soil moisture, a
more practical way based on observation for judging the right soil moisture for tillage work are:
a) the soil should slide freely from the disc or moldboard;
b) the soil must be friable or must break easily;
c) a freshly cut surface should not glisten with moisture;
d) squeezing a handful of soil should show no evidence of moisture.

Direction of tillage. The choice of direction in a square and nearly level field is not critical. On
rectangular fields, choose a direction that will allow greater efficiency and ease in doing the operation.
On rolling or hilly fields, follow the general contour of the land to prevent erosion.

2. Conventional method of preparing flooded soils (wetland preparation)

The traditional method of wetland preparation consists of three operations: a) irrigating the field
until it is saturated (or flooding); b) plowing (or primary tillage); and c) harrowing (or secondary
tillage).

Flooding the field. The field is flooded keeping the soil surface just covered with water 2 to 7 days
before plowing. This softens the soil.

Plowing. The first run of the plow is usually made near the base of the levee on a clockwise
direction. Subsequent runs of the plow are made to a depth of at least 15 cm and the direction depends
on the method of plowing employed. The field is kept flooded until the first harrowing.

Harrowing. Drain excess water and leave just enough to show the high and low spots in the field
just before the first harrowing. Soil clods are broken and the soil puddled by means of a comb or rake
harrow. Usually, three harrowings (alternating in direction with two lengthwise and one crosswise) are
sufficient to puddle the soil adequately.

If a rotavator is used instead of a plow in primary tillage, the number of harrowings may be reduced.

The final passing of the harrow should accomplish the levelling operation. The water is used as a
gauge in locating the high and the low spots in the field.

The soil is kept flooded between harrowings. If possible, wait for 7 to 10 days between successive
harrowings to allow surface weeds to germinate and to give time for the organic matter to decompose.

I. Characteristics of a well-prepared upland field (using conventional tillage)

 1. It must be granular and mellow yet compact enough so that seeds are in close contact with the soil for
seed germination.

2. It must be free of trash and vegetation to avoid interference with the seeding operation.

3. It must contain sufficient moisture to germinate the seed and support subsequent growth.

4. It must be level or without depressions where surface water may accumulate.

J. Characteristics of a well-prepared lowland field (using conventional tillage)

1. Weeds, rice straw and stubble that have been tilled under are thoroughly decayed.

2. Soil is well puddled and levelled for uniform distribution of water.

K. Choosing A Tillage System

In selecting a tillage system, the producer has to consider agronomic and economic factors. The
conventional tillage system is the standard against which others are compared.

The comparison is based on several criteria including the following: (1) proper seed placement, (2)
water infiltration, (3) pest control, (4) soil deterioration, (5) cost of machinery and equipment, and (6) crop
yields

Systems that leave large amounts of crop residue on the soil surface tend to interfere with proper seed
placement and covering. Similarly, conservation tillage systems interfere with fertilizer placement, while
encouraging the growth of perennial weeds. More efficient implements have been developed to overcome some
of these problems.

From the economic standpoint, the producer has to consider crop yield, cost of machinery and
equipment, and soil conservation. On the basis of yield, conservation tillage practices are known to produce
yields that are comparable to, or slightly lower than, those obtained from conventional systems. However,
conservation tillage systems have the added advantage of protecting the soil.

REFERENCES

Acquaah, G. 2002. Principles of Crop Production: theory, techniques, and technology. Pearson Education, Inc.,
New Jersey, U.S.A.

Bautista, O. (ed).1994. Introduction to Tropical Horticulture. SEAMEO-SEARCA and UPLB, Laguna.

Del Rosario, C.R. 1977. Land Preparation. In UPLB-CA. 1977. Multiple Cropping Source Book. Los Baños,
Laguna.

International Rice Research Institute. (Undated). Land Preparation. A slide-tape instructional unit (SR-3). Rice
Production Training Series. Los Baños, Laguna.

Lantican, R. M. 2001. The Science and Practices of Crop Production. SEAMEO SEARCA and UPLB

Ross, V. and Vo Tong Xuan. 1976. Training Manual for Rice Production. IRRI, Los Baños, Laguna.
 UNIT III

PLANTING

By

Dan Fred P. Castro

One of the cultural management aspects that is very important in establishment and high productiveness
of the crop is planting. Generally there are only two types of planting, and these are: direct planting and indirect
planting (transplanting).

Planting methods for lowland rice

1. Transplanting. This is most widely practiced in the Philippines and Asia. It is suitable for rainfed
(“palagad”) or adequately irrigated low lands. The advantages are: a) plants have a headstart in growth
over weeds; b) the crop stays for a shorter time in the field; c) ease in weeding operations.

Wetbed method of raising seedlings. Puddle plot 1 to 1.5 m wide and of convenient length is prepared. A total
of 400 sq. m. is needed to sow a bag of palay seeds of 50 kg to plant one hectare. Soil is fertilized with 4 kg of
(14-14-14) fertilizer. Seeds are pre-germinated (24 hours of soaking and 24 to 48 hours of incubation) then sown
at 1 kg per 10 sq m bed. Seedlings are continuously irrigated, protected from insect pests by applying Carbofuran
at 1.5 kg for the entire seedbed. The seedlings are ready for transplanting in 25 to 30 days.
Dapog method. Pre-germinated seeds are sown on cement or puddle soil covered with banana leaves or plastic
sheet or heavy coarse paper at 60 kg seed on 40 sq m plot to plant 1 hectare. Seedlings are ready for transplanting
in 10 to 14 days.
Dry-bed method. This is used for rainfed areas where the frequency and amount of rainfall are unpredictable
during the planting season. The seedbed is 1.5 m wide of convenient length. Fifty (50) kg of seed are sown on
500 sq m to plant a hectare. Unlike the wetbed method, the nursery bed is not submerged in water but kept moist
for most of the time. The seedlings are ready for transplanting in 20 to 42 days.

Transplanting distances:

- Square method from 18 cm to 25 cm with 2 to 3 ordinary seedlings or 4 to 6 dapog raised seedlings per
hill. This is the most common method.

- Wide rows, closer hills-40 cm x 5 cm, one seedling per hill or 30 cm x 13 cm with 2 seedlings per hill.

- Double row method- alternation of 20 cm and 40 cm row spacing with hills 10 cm apart and 2 seedlings
per hill.

2. Direct seeding on puddlled field

This has the advantage of less labor requirement in planting. However, the crop is vulnerable to
weed problems. Use of pre-emergence herbicide may be necessary.
Seeds are pre-emerged. Seed requirement is 100 to 125 kg/ha.

Methods:

a. Broadcasting as done by farmers, but the system is not desirable in terms of weed management.
b. Drilling the pre-germinated seeds in rows at 25 to 30 cm spacing. A mechanical implement, the “rice drum
seeder”, is used and rate of seeding is low at 50 to 100 kg/ha. It is advantageous in terms of better weed control
since a weeder can be passed between the rows.
c. Dibbling: pre-germinated seeds are dibbled in straight rows and in hills at 15 cm x 15 cm to 25 cm x 25 cm
with 5 to 8 seeds per hill. This will allow cross passings of the rotary weeder.

3. Dryland seeding of lowland rice. The field is prepared dry (unpuddled) and the operations are usually
started by plowing immediately after harvesting the preceding rice crop. Harrowing is done prior to planting and
furrows are laid out using the “lithao” method. With this method, seeds (non-germinated) are broadcast, then a
spike-tooth harrow is passed obliquely to the direction of the furrows to dislodge the seeds on the ridges and bring
them into the furrows. Another equipment, the “Inverted-T seeder”, may be used which can drill the seeds in
straight rows.
 The advantage of the dryland system of seeding is that the soil structure is maintained in good condition
and can be tilled easier for a second crop. The biggest disadvantage is in keeping the weeds under control.

Planting methods of upland crops (upland rice, corn, legumes)

In seeding upland crops, it is ideal if the initial dosage of fertilizer is applied simultaneously in one
operation. Contact between seeds and fertilizer should be avoided. The fertilizer will be a booster to the seedlings
and give them a good headstart.

There are several methods of seeding upland crops.

1. Broadcast sowing of mungbean on tilled and untilled paddy soil. It is preferable to pass a spike tooth harrow
over the field after broadcasting to partly cover and distribute the seeds evenly and avoid patchy growth.
2. Drilling seeds within the row for upland rice, peanut, sorghum, soybeans and mungbean using the “Inverted-T
seeder” which can be hitched to a hand-tractor or carabao-drawn.
Another practice in row-seeding is with the use of a combination of the “lithao” and peg-tooth harrow. In
this system, fertilizer is usually applied later in the seedling stage.
3. Seeding seeds in hills within the row. This can be accomplished with the use of a “rolling injection planter”,
the animal-drawn multicrop seeder-fertilizer applicator or a tractor-mounted planter.

Planting methods for vegetables

Direct seeding is the least expensive method of planting and establishing vegetable crops in the field.
While many vegetable crops can be successfully planted by direct seeding, environmental and biological factors
can affect resulting stand establishment. Preferably, transplanting is the better way of planting vegetables in the
field
Factors whether to direct seed or transplant is discussed at the preceding topics.

Growing of seedlings is usually practiced for vegetable crops like onion, leek, lettuce, broccoli, cabbage
cauliflower, mustard, etc.

Transplants must be in good condition when placed in the field. They should not be too large or hardened
too severe and should not have a large number of the roots removed by pulling the transplants out of the growing
containers.

Before putting a plant into a hole, a cup of starter solution is applied. Starter solutions are water-soluble,
high phosphorous fertilizers applied to young plants at the time of transplanting. Starter fertilizers supply
phosphorous in an available form even when the soil temperatures may restrict phosphorous uptake. Solution is
prepared by dissolving 24 gm of 12-24-12 fertilizer for every 10 liters of water, prepared few days earlier before
transplanting time.

Transplanting should be done in the afternoon and during cloudy days. Transplants are typically planted
1 to 2 in. deeper in the field than they were in the growing containers. The soil after the transplants are placed in
the field is well firmed around the roots.

Planting methods for perennial crops (fruits and plantation crops)

Direct planting

Direct planting may be done for some species whose seeds germinate easily and establish quickly. An
example is papaya in which 3 to 4 seeds are sown per hill but only one seedling is retained. Mango and cashew
seeds may also be planted directly.
Asexually propagated materials such as those used for pineapple, banana and abaca are planted directly
to the field.

Transplanting

Seedlings that have been grown in pots or plastic bags and attained the proper stage are transplanted. Holes
are made on the ground the size of which will depend on the characteristic of the soil and the crop. If the soil is
fertile and has a deep surface layer, a minimum size of hole just a little larger than the size of the plastic bag
container can be made.
In heavy soils which are infertile and with a shallow top layer and for crops that grow into a big tree, hole
dimension can be as large as one cubic meter. In planting, the excavated top soil should be returned first to the
bottom of the hole. The pot or plastic container is removed and the seedling is set firmly by refilling the space
with top soil and packed densely by thumping. Transplanting should be done at the start of rainy season.

High Density Planting

To attain a high density, the seedlings are set at a spacing several times (2 to 10 times) closer than the
conventional planting distance. The system produces greater yield per hectare especially at the early productive
years of the orchard. On a per tree basis, the yield is lower but this is more than compensated for by the greater
number of trees. At high density, the trees will not grow very tall as they will be subjected to regular pruning.
Thus, harvesting and other operations will be facilitated.

High density planting is accompanied by high management inputs, labor intensive and will entail high
costs. Negligence, of the orchard will result in overcrowding of the trees and a loss in fruit quality and
productivity.

High density planting will only be feasible if there are: good supply of water (irrigation or evenly
distributed rain throughout the year), high fertility of soil, and enough capital to support the greater number of
trees. Knowledge of the different cultural management practices especially in maintenance of the orchard or
plantation will also be critical factor.

METHODS OF PLANTING

Manual Seeding

Manual seeding involves the use of hand-held tools that may be as simple as a stick that is used to dig a
shallow hole in which seeds are placed. The seeds are covered with soil and lightly firmed. There is also the
manual jab planter, in which a hand-held tool is used to dig the hole, instead of a stick. Manual planting is practical
for seeding small fields.

Mechanized Seeding

Mechanized seeding is accomplished with three categories of implements: broadcast seeders, grain drills,
and row crop planters. Whereas equipment from any of the three categories described may be calibrated for
planting different kinds of seed, a fourth category of equipment, called specialized planters, is designed to plant
specific crops.

A mechanized seeder has three main parts: a hopper for carrying the seed and a metering device to deliver
seed to a drill that opens a furrow for seed placement.

Broadcast seeders- seeds are distributed in a random but uniform manner. The seedbed must be well prepared for
this operation to be successful. Broadcasting is usually followed by harrowing to cover the exposed seed with
soil.

Grain drills- grain drills are used when a high seeding rate is required, as in the seeding of small grains. Grain
drills can be fitted with accessories such as a fertilizer hopper to dispense fertilizer and seeds simultaneously.

Row-crop planters- these implements are used to plant seed such that the crop can receive post-establishment
husbandry by mechanized methods. These implements can be adjusted for planting seed in a drill pattern.

Two Types of Mechanical Seeders

Random seeders- are less precise in seed distribution and are usually designed to use gravity to distribute seed.
Random seeders sow a metered flow of seeds without exact placement or spacings of seeds.
 A seed drill is the most common type of random seeder. It has a rotating feed wheel that agitates the seed
over an orifice that causes the seed to fall at controlled rate. The seeding rate is adjusted by selecting specific
orifice size. A disadvantage of direct seeding with a random seeder is the need to thin the emerging seedlings to
desired plant spacings.

Precision seeders- are capable of metering seed to a high degree of accuracy for equidistant distribution and at a
specific depth in the soil. Precision seeders are more expensive than seed drills but using them reduces or
eliminates costs associated with the need for thinning after the seedlings become established.

Several types of precision seeders:

1. belt type
2. plate type
3. vacuum type
4. spoon type
5. pneumatic type
6. gel seeders

Mechanical Transplanter

Single-row and multirow mechanical transplanters drawn behind a tractor are available that will set bare-
root plants or rooted plants. A mechanical transplanter with a tractor driver and two additional people can plant
several hectares of plants in a day. Transplanters are also available that will punch holes into plastic mulch, set
plants, and also apply starter solution after the plants are placed into the soil.

Example of a mechanical transplanter

MODEL PF-455S
RICE TRANSPLANTER

SPECIFICATIONS:

TRANSPLANTING CAPACITY: 0.207 ha/hr

NUMBER OF ROWS: 4
ROW SPACING: 30 cm (fixed)
HILL SPACING: adjustable to three (3) settings (14.6 cm, 13.1 cm, 11.7 cm)
NUMBER OF SEEDLING PER HILL: 3.5
TRANSPLANTING SPEED: 0.34-0.74 m/sec
TRANSPORT SPEED: 1.44 m/sec
PLANTING EFFCIENCY: 90-95 %
PRIMEMOVER: 3hp – 4000 rpm 4-stroke gasoline engine

The PF-455S rice Transplanter model is one of the 34 sets of PhilSCAT’s (Philippine-Sino Center for Agricultural
Technology) agricultural machineries which is recognized as a new planting technology introduced to increase
rice production of Filipino farmers by reducing the usual drudgery and intensive labor in farm operations
particularly during transplanting.
This transplanter is designed for transplanting medium and small-sized seedlings. It is equipped with hydraulic
gauge finder which can adjust the state of machine according to the undulation of fields and rigid bottoms, and
keeps the balance of the machine and provides uniform transplanting depth. The index of basic seedling and
transplanting depth, among others can be adjusted through quantification. It features high level mechanical-
electrical integration and high working efficiency.

FACTORS TO CONSIDER WHETHER TO TRANSPLANT OR DIRECT SEED

Plant Factors.

1. Rate of root regeneration. Roots are always broken when a plant is transplanted. The top of the plant
cannot resume normal growth until the broken roots have been replaced and a balance in the root/shoot
ratio has been attained. Many crops such as sweet corn, okra, the legumes and the cucurbits are very slow
 in regenerating new roots. A layer of suberin is formed at an early stage in the root development of these
crops and it retards the formation of new roots. The slow root regeneration greatly retards the development
of the plants, causing a check in growth which is never corrected and which greatly reduces the ultimate
size and yield of the plant. Tomatoes, eggplant, peppers, cabbage and other crops that transplant easily
have rapid root regeneration if they have not been over-hardened.
2. Type of root system. Crops such as carrots, beets and radishes produce a long tap root which forms the
basic part of the root system. If the tap root is damaged, the root system is severely reduced in size. It is
hard to prevent damage to the tap root because the seedbox has a limited depth. In cases where the tap
root is fleshy and edible as in carrots and radishes, a broken tap root cause an odd-shaped, small,
undesirable root. Generally, plants with a more diffused root system or those with heavy branching like
tomatoes, cabbage and onions can be transplanted without any problem.
3. Days from seed to harvest. Transplanting slows development by one, two, or more weeks, the shorter
time occurring when special care is given to the transplants. If seven to fourteen days are added to the 110
days required for tomatoes to reach maturity, the growth period is increased by an average of nine percent.
Pechay and lettuce which require only 42 days from seed to harvest would have their growth period
increased by an average of 25 percent. While the extension of the growth period maybe relatively
insignificant to a tomato grower, it is quite significant to a farmer growing leaf lettuce, pechay or mustard.
4. Seed size. Some crops such as corn, okra and beans have large seeds that can be planted easily on a wide
range of soil conditions. Seedlings produced from these crop seeds are large and grow fast. Crops such as
tomatoes and cabbage have smaller seeds, produce smaller seedlings and have a very narrow range of
tolerable soil conditions under which the seedlings will grow well and become established if direct-seeded.
Large seeds can hold a larger amount of protectant fungicides and insecticides when treated than the
smaller seeds. This makes the smaller seeds more susceptible to attack of insects and pathogens.
5. Rate of seed germination and seedling growth. Some crops such as pechay, sitao, corn, and radish
germinate rapidly and their seedlings grow fast. This makes them easier to direct seed than crops like
tomatoes and cabbage which germinate and grow slowly in the first few weeks. The seeds of the latter
must be kept under conditions favorable for germination over a much longer period of time so the
seedlings are at the stage of development most subject to damping-off for a longer period of time.
Transplanting crops which exhibit slow germination and seedling growth enables the grower to provide
more favorable conditions for rapid seedling growth and to hasten the over-all development of the crop.

Economic factors

1. Size of the farm. Small farmers and home gardeners generally use the transplant method for
vegetables since they cultivate only a small area which must be used to its fullest in order to maximize
profits. Availability of labor is generally not a problem, so crops that begin small but have a large
space requirement at maturity are transplanted. This way, the plant can be grown close together when
they are small and can be grown farther apart when they require more space at the stage of rapid
growth. In large commercial plantings direct seeding is recommended because transplanting will
entail a considerable expense of time and labor. Operations commonly done for seedling care can be
dispensed with, like pricking and blocking.
2. Purpose for which vegetable is grown. Another economic factor that must be considered is whether
the crop being grown is intended for the fresh or processing market. Growing crops for fresh market
requires higher production cost per unit of marketable product but the return generally provides a
greater net profit per unit sold. As a general rule, crops for the fresh market commands a better price
than crops for processing. Consequently, the grower producing for a fresh market can afford for
transplanting cost which the grower producing for a processor cannot afford.
3. Availability and cost of seeds and labor. Direct seeding requires at least three to four times as much
seed to insure a good stand and as much as eight to ten times the amount needed for a careful transplant
operation. If the transplant operation includes a preliminary pricking and spotting operation, every
seedling can be used, a fact which is important when seeds of a new variety is available only in limited
quantity and at a higher price.

DEPTH OF SEED SOWING, PLANT DENSITY, PLANT ARRANGEMENT

After selecting the appropriate cultivars and preparing the seedbed, the producer has three decisions to
make towards crop establishment, and these are:
Depth of Sowing

The selection of the correct depth of sowing for any crop is based on the conflicting needs to plant deeply
enough to protect the seed from desiccation/drying out within the surface layer of soil, yet shallow enough to
permit easy and rapid emergence of the shoot.
If seeds are sown at different depths, germination will be uneven, resulting in an uneven crop stand, which
will, in turn, affect later crop production activities, such as harvesting. The crop would mature unevenly and hence
present a problem for mechanized harvesting.
Depth of seed placement is influenced by several factors, including seed size, type of seedling emergence,
soil type, and soil moisture.

1. Seed size. Large seeds have more food reserves and can emerge from lower depths in the soil while
depending on stored energy. Small seeds have small food reserves and therefore restricted elongation
potential. This necessitates much shallower sowing depths.
2. Type of seedling emergence. Species with epigeal germination-where the cotyledons are brought above
the ground - need to emerge above the soil to commence seedling establishment. If planted too deeply in
the soil, emergence may be greatly delayed, and seeds may rot in the process.
3. Soil type. A heavy soil (clay) is cold, poorly drained and aerated, and also prone to crusting. Seed
placement in such a soil type should be shallow in order to provide a more favorable environment for
germination. Light soils (sandy), on the other hand, drain freely and prone to drying, especially in the soil
surface. They also provide less impedance to emergence. Seed maybe planted deeply in such soils.
Shallow planting may cause seeds to dry after imbibing water.
4. depth of soil moisture available. This feature is associated with soil type. Clay soils have higher water-
holding capacity than sandy soils. The top of sandy soils is prone to drying. Where supplemental moisture
will not be applied during production, the depth of soil moisture will be low in the sandy soils,
necessitating a much deeper seed placement.

Plant Density

Plant density is determined by the seeding rate of a crop, or the number of established plants per unit land
area. The seeding rate should be estimated as closely as possible for optimal crop establishment. Overseeding
(which causes intense competition among plants) or underseeding (which results in underutilization of resources)
can reduce crop productivity. The seed needed to plant an area is estimated as weight, not count.
Seeding rate of some of the major field crops and horticultural crops are presented in the readings of
laboratory manual.

Plant Arrangement

Plant arrangement in the field is influenced by some of the factors that influence plant density. Seeds may
be distributed in the field according to a predetermined, constant, and uniform spacing pattern, or randomly
distributed. Distribution pattern depends on factors including seed size and production system. The common types
of distribution of plants in the field may be categorized into two: random distribution or patterned (structured)
distribution.
Discussion of broadcasting and patterned distribution are discussed in readings of the laboratory manual.

REFERENCES

Acquaah, G. 2002. Principles of Crop Production: theory, techniques, and technology. Pearson Education, Inc.,
New Jersey, U.S.A.

Bautista, O. (ed).1994. Introduction to Tropical Horticulture. SEAMEO-SEARCA and UPLB, Laguna.

Coronel, E. 1985. Planting and Care of Fruit Crops in the Home Garden. IPB, UPLB, Laguna

Lantican, R. M. 2001. The Science and Practices of Crop Production. SEAMEO SEARCA and UPLB

PCARRD. 19__. The Philippines Recommends for: Mango, Citrus, Banana, Coconut, Coffee, etc.

DA brochures on different crops.

 17
UNIT IV

WATER MANAGEMENT

By

Justo G. Canare Jr.

Crop production in some parts of the world is impossible because of lack of water; in others there is excess.
An average annual precipitation (rainfall) of 510 mm is considered the minimum for cropping without irrigation.
With less than 250 mm rainfall per year, desert conditions prevail.

Water management involves interrupting and manipulating various stages of the hydrologic cycle to make
water available, to remove it where there is an excess and to improve the quality when necessary. The water
management in relation to crop production involves irrigation, drainage and conservation. Only the first two will
be discussed in this unit.

IRRIGATION

Essentially, irrigation is a method whereby water is provided for plant growth when the supply of moisture
or rainfall is inadequate. Aside fro supplying the water required for plant growth and development, irrigation
helps to control soil and air temperatures and to leach the soil of excess soluble salts.

In present irrigation practice, supplemental water may be applied in three general ways, namely:

1. surface irrigation
2. sprinkler or overhead irrigation
3. sub-surface irrigation or sub-irrigation

Surface irrigation (also called gravity irrigation). The water is applied on land that has sufficient slope
to permit flow over the surface by gravity. This method is accomplished in the following ways:

a. Flood irrigation – water is allowed to cover the entire surface of the field in a continuous sheet.
It is frequently used for crops that form a complete ground cover such as permanent pasture and
rice. Under this method are surface flooding and contour flooding.

b. Furrow irrigation – water runs down the furrows between the plant rows (not over them) and
down to all parts of the soil by capillary action or gravity. Contour furrows can be used effectively
when slopes do not exceed 10-15 percent.

Advantage – under ideal condition, no source of energy is required for the final distribution of
water.

Disadvantage – since the system depends on gravity, it is inefficient in that more water is required
than is actually delivered to plants. Also, there is possible degradation of soil structure.

c. Trickle or drip irrigation – small amounts of water are applied at frequent intervals through tiny
holes or valves in plastic pipes on the soil near each plant, where a wet area is formed that extends
to the plant’s roots. It is usually used for high-value agronomic or horticultural crops.

Advantages

Trickle irrigation is replacing surface irrigation in some areas where:

 18
▪ Water is scarce or expensive,
▪ The soil is too porous or too imperious for gravity (flood or furrow) irrigation,
▪ Land leveling is impossible or very costly,
▪ Water quality is poor,
▪ It is too windy for sprinkler irrigation,
▪ Trained irrigation labor is not available, or
▪ Irrigation labor is expensive.

Trickle irrigation not only improves the efficiency of water use but also gives much greater control over
the placement and amount of water. The amount of water can be adjusted to the soil’s absorptive capacity and to
the characteristics of the particular crop, its stage of growth, and the climatic conditions.

Fertilizers can be applied through the trickle system (the practice of applying fertilizer with irrigation
water is called fertigation) and efficiently applied close to the roots. Because the irrigation water never touches
the leaves, foliar salt damage is not a hazard with trickle irrigation.

Many moisture-induced leaf and stem diseases (e.g. fungal diseases) fostered by other methods of
irrigation are minimized or defeated by trickle irrigation, which may also help control pathogens that develop in
waterlogged soils.

Because trickle-irrigation water drips onto the soil without disturbing the surface, soil erosion and surface
crustation, which impede water penetration or infiltration, are usually eliminated.

Limitations

There are some serious technical problems with trickle irrigation. The primary problem is clogging of the
emitters by:

▪ Precipitates from limestone-containing waters

▪ Precipitates from iron-containing waters
▪ Algae
▪ Suspended silt, clay, or fine sand.

Sprinkler irrigation. A sprinkler unit consists of a pumping unit, mainline pipe unit, lateral pipe unit and
sprinkler unit. Water may be applied through sprinkler heads or perforated pipes. At present, the use of
lightweight, easily movable aluminum pipes with rapid coupling devices has cut labor cost and brought the
practice into general use.

Sprinkler heads, the most popular types, may be used with permanent buried lines or temporary portable lines.
Water is delivered through sprinkler heads mounted on riser pipes. Because each sprinkler head applies water
to a circular area, distribution is not uniform.

Perforated pipe sprinkler delivers water through small holes drilled along the length of pipes mounted on
permanent supports.

Advantage – water can be applied precisely and uniformly to all kinds of soil and crop in the exact amount
required.

- land preparation is not necessary

Disadvantage – initial cost and power requirements are high.

- water must be clean; otherwise, it will clog the spray

equipment

- in hot dry regions, evaporation may consume a significant amount of the water while it is in the air.

- distortion in the spray pattern due to wind movement

 19

Sub-irrigation. The distribution of water to soil below the surface. The objective is to create an artificial
water table from which water can move upward by capillary action. The two types are open ditch and underground
conduit.

Sub-irrigation is possible only when the topography is absolutely level. In addition, there must be a barrier
against the irrigation pipe to prevent the loss of water down through the soil by percolation. The barrier may be a
water table that is not high enough to provide adequate moisture to the root zone or it may be an impervious soil
horizon.

Factors determining the feasibility of irrigation under a given condition and the type of irrigation to be
adopted include among others:

a. Soil characteristics
b. Crop to be grown

Soil characteristics - texture, structure and porosity relate directly to the water-retaining and water-
transmitting properties of soils. Below is a table showing the influence of texture on soil water characteristics.

AWHC
Soil Texture FC (%H2O) PWP (%H2O)
%H2O mm H2O
Sand 6.7 1.8 4.9 19.75
Silt 32.2 11.8 20.4 62.75
Clay 39.4 22.1 17.3 48.25
FC (field capacity) – when all free or gravitational water has drained from the soil.
PWP (permanent wilting point) – when all the capillary water has been depleted.
AWHC (available water holding capacity) – water available to plants.

It is important to consider the influence of structure in soils of the same textural class. For example, a
well-structured clay soil will be more permeable than one that is poorly structured. The well-structured clay soil
can exhibit water infiltration and transmission characteristics similar to that of a coarser textured soil, such as
loam.

Crops to be grown. Irrigation practices must be adapted to the nature of the crops being grown and
especially to their rooting habits and soil water management. The consumptive use of water is defined as the total
quantity of water transpired by the crop plus that evaporated directly from the soil on which the crop is growing.

Crops differ in depth of their root zone and the deeper-rooted ones will require less frequency of irrigation
because they can draw moisture from the deeper layers of the soil. Some crops can tolerate moisture stress more
than others because they have mechanisms for stomatal closure, which diminish the rate of transpiration.

Below is a table showing the root zone depth and consumptive use of some crops.

Crop Root Zone Depth (cm) Consumptive Use (cm)

Cabbage 41-61 30
Cassava 90-120 50-250
Corn 100-170 55
Cotton 100-170 70-80
Eggplant 90-122 48
Garlic 46-61 36
Lettuce 46-61 30
Mungbean 60-90 41
Mustard 91-122 41
Okra 91-122 30
Onion 46-61 46
 20
Peanut 40-80 50-60
Pechay 91-122 30
Soybean 60-120 53
Sugarcane 120-200 132
Tomato 120 46
Watermelon 100-150 46

Determining Irrigation Requirements

Irrigation that is capable of yielding many benefits may be wasteful and even harmful if it is applied
incorrectly. The determination of when to irrigate and how much water to apply in relation to economic crop
production is a critical part of irrigation technology. The timing of application in relation to the growth stage of
the plant is also critical.

There are two approaches to determine irrigation requirements. One consists of actual measurement of
soil moisture and subsequent calculation of valuable moisture. The other consists of calculating available water
from meteorological data.

Irrigation is most efficient if applied before soil moisture becomes limiting to plants. As a rule of thumb,
water should be applied when 60 percent of the available water in the root zone has been depleted. To determine
when irrigation is required, it is first necessary to determine how much water is already in the soil. From such
measurement, the availability of water to plants can be determined.

However, the two approaches mentioned above require instruments and some technical knowledge. They
are useful and effective in large farms. For small farms, visual symptoms of water stress and the feel of the soil
can be used as guides (see the chart on the next page).
 21

Practical Interpretation Chart for Soil Moisture

% of useful
soil moisture Feel or Appearance of Soil
remaining Coarse Light Medium Heavy
0 Dry, loose, single- Dry, loose, flows Powdery, dry, Hard, baked,
grains flow through through fingers. sometimes slightly cracked, sometimes
fingers. crusted but easily loose crumbs on the
breaks down into surface.
powdery condition.
50 or less Still appears dry; Somewhat crumbly; Somewhat pliable;
Still appears to be
will not form a ball but will hold will ball under
dry; will not form a
together from pressure.
ball with pressure.
pressure
50 to 75 Tends to ball under Forms a ball; Forms a ball; will
pressure but seldom somewhat plastic; ribbon out between
-do- holds together. will sometimes slick thumb and
slightly with forefinger.
pressure.
75 to FC Tends stick together Forms weak balls; Forms a ball and is Easily ribbons out
slightly, sometimes breaks easily, will very pliable; slicks between fingers; has
forms a very weak not slick. readily if relatively a slick feeling.
ball under pressure high in clay.
FC Upon squeezing, no (Same as Coarse) (Same as Coarse) (Same as Coarse)
free water appears
but wet outline of
ball is left on hand
Above FC Free water appears Free water will be Can squeeze out free Puddles and free
when soil is bounced released with water water forms on
on hand kneading surface

FC – field capacity Note: Ball is formed by squeezing a handful of soil

very firmly with fingers.
 22
DRAINAGE

Definition of Terms

Drainage - removal of excess water from the soil.

Surface drainage - removal of excess water on the soil.
Internal drainage - removal of excess water by downward flow through the soil.

What happens during a heavy rain?

In the rainy season, the soil initially absorbs water until it reaches its saturation point or maximum water-
holding capacity. As rain continues to fall, some of the water percolates due to the pull of gravity. The excess
over that which percolates stays on the surface and accumulates in low-lying areas.

If the soil is coarse-textured, the surplus is easily drained. If the soil is fine-textured, the clay particles
swell on wetting, closing the larger pores through which the water was draining.

Under such condition, the excess water will remain on the surface unless removed by surface drainage.

Generally, the problem of drainage may be due to:

a. persistent standing water on the soil surface

b. presence of excessive soil moisture within the root zone
c. both

What is a well-drained field?

a. If after a heavy rain, no standing water is left in the field.

b. If 48 hours after a heavy rain, no free water is present within a depth of 2 ft
(60 cm) of the soil profile.

Why is drainage important?

a. for better germination of seeds

b. for healthy root system
c. for efficient utilization of fertilizer
d. for good growth
e. for timely land preparation and harvesting

The process of growth is supported by energy produced during respiration, and respiration needs oxygen.
Oxygen can only be present if the macropores of the soil are empty of water.

Oxygen is essential to root growth and aerobic respiration. Prolonged submergence of the root results in
the death of root hairs, which are mostly responsible for absorption. Even the older roots decompose.

The above condition will result to lower rate of absorption of water and nutrients, so much so that under
waterlogged conditions some plants, such as sugarcane, exhibit symptoms of drought (curling of leaves). They
also exhibit symptoms of nutrient deficiency. This is due not only to the death of roots but also to the fact that
absorption, being an active process, is supported by respiration, which is impaired in poorly-drained soils.

Nutrients may be abundant in the soil, but largely unavailable to plants if the soil air supply is inadequate.
Moreover, microorganisms in the soil that make nutrients available require oxygen.
 23
Removing excess water from soils

a. Improve internal drainage. If impermeable hardpans are present, break them by subsoiling. Maintain
structure of soil by timely land preparation, green manuring, and addition of organic matter.

b. Drain surface water. A complete drainage system usually consists of an interconnected series of
field drains, leading to farm or secondary drains and finally to main drains or natural waterways like rivers or
streams.

Main drains are normally open ditches designed to carry volumes of water leading to natural waterways
or outlets. Main drains may take water from one big farm or several farms. Periodic clearing of the canal is
necessary to avoid clogging and weed infestation.

Farm drains. The farm drains handle the water collected from field drains for conveyance to the main
drain or normal waterway. Farm drains are smaller in capacity than main drains and carry only drainage water
from within the farm. Ditches are generally used although large pipe drains have been employed. Pipe drains are
more expensive to install but cheaper to maintain if provided with adequate inspection boxes.

Field drains. There are two kinds of field drains – surface systems and underground systems or
subsurface drains.

The choice between these two systems should consider the following:
a. soil characteristics
b. root habit of crop
c. nature of drainage problem
d. amount and intensity of rainfall
e. capital investment

Surface systems consist of open ditches that carry water to the farm drains.

Subsurface drains, also called underdrains, are underground artificial conduits for conveying excess
soil moisture out of the field. The most widely used subsurface drains are the tile and mole drains.

Tile drains consist of clay or concrete pipes or tiles laid end to end and forming a uniformly graded line
into which water percolates at the joints to an outlet. Tile diameter varies from 3 to 8 inches. Generally, tiles are
made in 12, 18, and 24-inch lengths.

To install a tile drain system, a trench is constructed with its bottom graded where the tiles are laid end to
end. The joints are then covered with trash or other filtering materials to prevent silt or soil particles from getting
inside the line. Backfill is then placed so that nothing shows on the surface,

If the tile drain discharges to an open canal, stones are placed under the outlet to protect from scouring.
The tile end must be covered with mesh wire to prevent rodents and other animals from getting inside and clogging
the line. Also, the tile end elevation must be higher than the level of peak flow in the outlet canal.

In some areas, bamboo is used instead of tiles. Under normal conditions, bamboo tubes may give
satisfactory service for about eight years. In general, tile drain is expensive.

The use of an unlined channel called mole drain, 3 to 6 inches in diameter has been popular in many areas.
It is created by drawing a torpedo steel mole uphill through the soil. Mole drain is simple, efficient, and is
inexpensive to construct. However, it can be best employed only in uniform stable soils.

Starting from an outlet canal, the mole is drawn uphill by a tractor forming an unlined channel where the
mole passes. Since the mole is attached to a subsoil standard, the soil profile above the mole is shattered, creating
a fissure, which drains into the mole channel itself. Mole drain is usually drawn 24 to 40 inches deep. Spacing of
mole lines varies from 5 to 10 feet in heavy soils, and from 15 to 25 feet in lighter soils. Channel grades of 2.5 to
3.5 percent are most preferable.
 24
Mole drains may last from 1 to 10 years depending on existing conditions. The best time to install mole
drains is when the soil surface is dry and firm enough to support the power unit (the tractor) and the subsoil is
sufficiently wet to produce a smooth channel behind the mole plug. When the soil is too dry, power requirements
are high and excessive fracture of the soil takes place. Thus, a smooth stable channel cannot be formed.

REFERENCES

Acquaah, G. 2002. Principles of Crop Production: theory, techniques, and technology. Pearson Education, Inc.,
New Jersey, U.S.A.

Bautista, O. (ed).1994. Introduction to Tropical Horticulture. SEAMEO-SEARCA and UPLB, Laguna.

Caoili, A. 1977. Irrigation Methods for Upland Crops. In Multiple Cropping Sourcebook. UPLB-CA.

Caoili, A. 1977. Water Use and Management Requirements for Lowland Rice. In Multiple Cropping
Sourcebook. UPLB-CA.

Lantican, R. M. 2001. The Science and Practices of Crop Production. SEAMEO SEARCA and UPLB

Orcullo Jr., N.A. 1997. Irrigation Systems Handbook. Institute of Agricultural Engineers, Manila.

Turner, A.K. 1984. Soil-Water Management. IDP, Canberra, Australia.

NAS. 1974. More Water for Arid Lands. National Academy of Aciences, Washington, D.C., USA.
 25
UNIT V

NUTRIENT MANAGEMENT

By

Justo G. Canare Jr.

The growth and development of plants are determined by numerous factors of soil and climate and by factors
inherent in the plant themselves. Basically, plants rely on the soil to provide nutrients and water. If a soil is to
produce crops successfully, it must have, among other things, an adequate supply of all the necessary nutrients
that plants take from the soil. Not only must required elements be present in adequate amounts, but also in forms
that plants can use and in proper proportions. Otherwise, normal plant growth will not occur.

Soils differ in their native fertility or inherent capacity to supply nutrient elements to plants. This is due to
varied soil characteristics and other factors affecting these characteristics. For instance, soil texture can greatly
influence the availability of nutrients to plants. Clay, the smallest soil particles, can adsorb nutrients and prevent
them from being carried down with drainage water, which a sand particle cannot do. A clayey soil will therefore
have a greater capacity to store nutrients in their plant available forms than a sandy soil.

However, though a soil may be originally fertile, its fertility may be lost after some time. This low fertility is
generally the cause of low crop yields in the country.

People have little control over other factors of growth like air, light, and temperature, but can influence the
supply of plant nutrients in the soil. They may increase the supply of available nutrients by modifying soil
conditions or by making additions in the form of fertilizers.

The Essential Elements

The essential elements required by plants are divided into two groups known as the macro (or major) and
micro (or trace or minor) elements. These two groups are not designated to denote the relative importance of the
elements in plant nutrition but to indicate the relative proportion of each that is required for satisfactory growth.
Sixteen elements are currently considered essential. The macroelements are carbon, hydrogen, oxygen,
nitrogen, phosphorus, potassium, calcium, magnesium and sulfur. The microelements are manganese, iron,
boron, zinc, copper, molybdenum, and chlorine
More than 40 additional elements have been found in plants. An example is silicon, which has a beneficial
effect because it imparts structural strength to many plants. Still, these elements are not considered essential
because they do not satisfy the criteria for essentiality.
As early as 1939, Arnon and Stout set the criteria for essentiality as follows:
1. If a deficiency of the element prevents the plant from completing its life cycle.
2. If the deficiency symptoms of the element in question can be prevented or corrected only by supplying
the element.
3. The element must be directly involved in plant nutrition not indirectly through correcting some
microbiological or chemical conditions in the soil or culture medium.

Ideally, a soil must be able to supply all the essential elements, but this seldom happens. However, even
assuming that a soil is capable of supplying these elements, it cannot remain so for a long time.

Decline Of Soil Fertility

The supply of available nutrients in the soil may be reduced through a) removal of crops, b) conversion to
unavailable forms, c) gaseous losses, d) leaching, and e) soil erosion.
 26
Crop removal. A crop absorbs nutrients from the soil which are subsequently used to support its
vegetative and reproductive activities. Different crops have varying capacities to absorb nutrients from the soil
(Table 2). Some crops absorb more of a certain element than others. For example, grain crops remove more
nitrogen from the soil than any other essential element, while forage, vegetables, sugarcane, root crops, and fiber
crops absorb a lot of potassium. Furthermore, a crop producing a high yield removes more nutrients from the soil
than the same crop producing a low yield.

Table 2. The amount of nutrients removed by crops at certain yield levels (various
sources)
Amount of Nutrients Removed
Crop (kg/ha) Yield Level
N P2O5 K2O
Rice 65 20 75 100 cavans palay
Corn 128 48 140 70 cavans grain
Sorghum 110 25 100 3.5 tons grain
Sugarcane 160 100 340 100 tons cane
Cassava 124 104 217 60 tons
Sweet Potato 70 20 110 15 tons
Mungo 70 30 40 1 ton grain
Soybean 140 22 110 2 tons grain
Conversion to unavailable forms. Conversion of nutrients to forms not directly usable by plants generally
takes place through: 1) chemical combinations with other elements to form water-insoluble components (such as
what happens in the fixation of phosphorus under highly alkaline or acidic conditions), and 2) microbial
transformations.
Gaseous Losses. Losses through transformations into gaseous forms (volatilization) are especially true for
the nutrient element nitrogen under flooded paddy conditions. The loss of nitrogen in the form of ammonia (NH 3)
gas may occur from floodwater on a soil moderately to slightly acidic although losses are usually highest on
alkaline soils. The higher the soil pH the higher the potential losses. Nitrogen may also be lost by denitrification
in which it is converted to N2O and N2 gas.

Leaching. Leaching refers to the process by which soil nutrients are washed down by water from the root
zone of the plants. The extent of losses vary with the nutrients, soil type, management, and climate. Greatest
leaching usually occurs in well-drained, course-textured soils (ex. sand and sandy loam) and during the rainy
season.
Soil Erosion. The surface soil is the most fertile layer of the soil but if left unprotected by crop cover it may
be slowly removed by surface run-off. The loss of organic matter and mineral colloids represents losses in plant
nutrients.

Soil Fertility Practices

The maintenance of soil fertility is very important in crop production. This can be done by: a) proper tillage,
b) organic matter maintenance, c) covercropping, d) crop rotation, and e) fertilization.
Proper Tillage. Tillage, when properly done, can help maintain soil fertility. Under upland condition, a
desirable soil structure (well-aggregated and porous) is maintained with proper tillage. This promotes water
infiltration and reduces surface run-off, thereby reducing erosion. The same result is obtained by contour tillage
in sloping areas. Improperly done, tillage can be a major cause of soil erosion, and consequently nutrient losses.
When a soil is over-pulverized by excessive tillage, it forms a crust on the surface upon wetting. This crust has
low permeability to water and results in greatly increased run-off and erosion. Tilling up and down in a sloping
area also makes erosion serious. Under lowland condition, proper tillage practices can conserve nitrogen released
in the decomposition of organic matter. A well-puddled surface soil together with a hard pan below can reduce
percolation and thus also reduce leaching losses.
Organic Matter Maintenance. Organic matter is an important ingredient of the soil as it supplies some of
the nutrient requirements of the crop and it promotes favorable soil properties such as granulation and good tilth
 27
for efficient aeration, easy root penetration and improved water-holding capacity. Organic matter or humus
(decomposed or partly decomposed animal and plant residues) makes soil granules or aggregates more stable
making them less susceptible to erosion. The supply of organic matter can be maintained by the application to
the soil of crop residues, farm wastes, compost, farm manures, green manures, and other forms of organic matter.
Covercropping. A cover crop is any crop planted primarily to protect the soil surface by reducing erosion.
Aside from this, it also reduces leaching of nitrogen and potassium, and possibly other elements, from the soil. It
also contributes to the store of organic matter in the soil. Cover crops may be planted in-between permanent
crops as in plantations or between crops in a rotation.
Crop Rotation. A well-designed cropping sequence can contribute to the maintenance of soil fertility. It
provides a full cover on the land for most part of the year, if not throughout the year, thereby minimizing soil
erosion. It keeps soil fertility at a high level through a proper rotation of clean-tilled crops and organic matter-
builder crops. This is generally done by planting a grain crop, such as rice or corn, followed by a legume, such
as soybean, peanut, mungo or cowpea.
Fertilization. Since the fertility of the soil is depleted continuously with cropping, no soil management
practice is complete and successful without replenishing the soil supply of nutrients through fertilizer application.
For fertilization to be successful, one must know what nutrients to supply and how much, what kind of
fertilizer to supply and how much, when to apply the fertilizer and by what method.

Methods Of Assessing Soil Fertility

The kind and amount of nutrients that must be supplied to a crop are determined by the following methods:

A. Visual symptoms of nutrient deficiency in plants

If a plant is not adequately supplied with a certain nutrient, it will exhibit outward manifestations or
symptoms of the deficiency. This way, one knows what nutrient to apply. This method, however, has
some limitations. Plants may not show deficiency symptoms unless the deficiency is severe. The
diagnosis may be hampered when deficiencies of more than one nutrient are present. Also, the fertilizer
applied to correct the deficiency may not benefit the crop because the application was too late. Or, it may
benefit the affected plants but not as much as it would if had been applied earlier.

B. Soil tests

Soil tests consist of actual chemical analysis of soil samples to determine the amounts of available
nutrients in the soil. The results are then compared with the optimum amounts the soil must contain for a
particular crop. If the results of the analyses are short of the optimum amounts, the balance is added
through fertilizers.

C. Plant tissue analysis

The nutrient content in the plant tissue is related to the available nutrient supply of the soil. Thus, a
chemical analysis of the plant tissue would reveal the available nutrient status of the soil on which the
plant was grown. When correlated with the results of fertilizer field trials, fertilizer recommendations
using this method become more reliable.

D. Fertilizer field trials

When employed singly, this is the most reliable method of assessing soil fertility. The effect of
fertilizer is assessed under actual field conditions in the presence of other factors of crop growth. Thus,
interactions of all these factors are taken into account. However, the information comes too late to benefit
the crop tested. It is useful for the future and for interpreting the results of cover types of tests.

Fertilizers And Fertilizer Materials

 28
A. Fertilizer defined

- it is material that supplies nutrients to plants (Janick, et al, 1974)

- it is any organic or inorganic material of natural or synthetic origin which is added to a soil to
upgrade its fertility to a level required by a crop (Phil. Recommends for Soil Fertility Management, 1982)

- it includes any substance, singly or in combination with other materials applied directly to the soil
for the purpose of promoting plant growth, increasing crop yields or promoting their quality (FPA, 1977)

B. Two general types of fertilizer

1. Organic fertilizers - are generally described as compounds which contain the carbon atom (other
than carbonate) as an essential ingredient. These include: a) natural organic materials which are plant or
animal residues such as farm manures, composts, crop residues, guano, “night soil”, green manures, etc.,
and b) synthetic organic materials such as urea, calcium cyanamide and urea-form.

2. Inorganic fertilizers - these include the: a) natural inorganic materials such as the Chilean nitrate
of soda, rock phosphate and most of the potassium materials; b) synthetic inorganic materials which are
products of chemical reactions of certain raw materials, such as ammonium sulfate, superphosphate and
ammonium phosphate.

C. Classification of fertilizer materials according to the number of fertilizer elements present.

1. Single fertilizer - contains only one fertilizer element. Example: urea, ammonium sulfate, single
superphosphate, muriate of potash

2. Incomplete fertilizer - contains two fertilizer elements. Example: ammonium phosphate,

monoammonium phosphate

3. Complete fertilizer - the material that is guaranteed to contain all the elements N, P, and K.
Example: 14-14-14; 12-24-12.

4. Mixed fertilizer - a material containing two or more of the elements which are supplied by two or
more fertilizer materials.

Methods Of Fertilizer Application

A. Broadcast application

This consists in spreading the fertilizer uniformly over the whole area usually before the last harrowing
or before seed sowing.

B. Topdressing

This refers to broadcast application over the already established crops. It generally applies to nitrogen
fertilizers and is used where localized placement is not practical. It is practiced in rice, pastures and lawns.

C. Sidedressing

This is a method of placing fertilizer to or beside the rows of crops such as corn, or placed around the
plants or trees.

D. Localized placement

This involves the placement of fertilizer near the root zone of the plants. This may be in the form of
a continuous band, heaps, pellets or balls. This is usually resorted to when limited amount of fertilizer is
 29
used or precautions are being taken to reduce fertilizer contact with the seed. This method of application
is especially necessary in the case of phosphorous fertilizers. Band placement of fertilizer to row crops is
usually with the aid of fertilizer drill so designed that the fertilizer falls at a fixed distance below and at
the side of the seed. The fertilizer may also be placed at the bottom of the furrow. Then the soil is bedded
back on the row before planting. The thing to remember is that the fertilizer must not be in direct contact
with the seed. This is by putting the fertilizer band about 5 cm away and below the seed.

E. Foliar application

This involves dissolving the fertilizer material in water and then applying it to the aerial portion of the
plant. Crop response to nutrient sprays is more rapid, but also more temporary than response to soil
application. So far, the most important use of foliar sprays has been in the application of microelements.
The greatest difficulty in supplying nitrogen, phosphorus and potassium in foliar sprays is in the
application of adequate amounts without severely burning the leaves and without an unduly large volume
of solution or number of spraying operations. However, foliar sprays are an excellent supplement to soil
applications of the major elements.

F. Applied with the seed

Application of fertilizer with the seed is done either by broad-casting together with the seed or coating
the seed with the fertilizer by means of an adhesive such as Cellofas A, or gum arabic. Coating seeds with
fertilizer (such as phosphate fertilizers) is known as pelleting which is usually employed when sowing
legume seeds (especially of forage legumes) on acid soil.

G. Fertigation

The fertilizers are dissolved in water and applied with the irrigation water.

Time Of Fertilizer Application

To be effective, fertilizer must be applied when the plant needs it. In the case of field crops, such
stages are: a) the early vegetative stage b) the active growth stage and c) the onset of flowering. However,
the timing of fertilizer application depend not only on the crop but also on the nutrient, the soil type and
the climate. Thus, nitrogen which is susceptible to leaching loss is applied a short time before it is needed
by the plant. For example, in lowland irrigated rice, nitrogen is applied before the last harrowing to take
care of the N requirements during the vegetative phase and again at panicle initiation stage to supply the
N needs during the development of the panicle. On the other hand, phosphorus and potassium are less
mobile in the soil and may be applied only once and that is before planting. A sandy soil has less capacity
to store nutrients than clayey soils. Thus, more frequent application of leachable elements is necessary.
Climate also affects the timing of application. For example, in corn and sorghum, all the recommended
amount is applied just before planting during the dry season. During the wet season, one-half of the N
and all of the P and K are applied just before planting and the rest of the N is applied before hilling-up.

In all these factors, the underlying reason is the capacity of the soil to keep the elements within the
reach of the roots of plants.

Amount Of Fertilizer To Apply

In computing the amount of fertilizer to be applied, one must know the recommended rate and the grade
of fertilizer which will serve as source(s) of the nutrients to be applied.

The fertilizer grade or analysis refers to the minimum guarantee of the nutrient content in terms of percent
total N, percent available P2O5, and percent water soluble K2O in a fertilizer. For example, the fertilizer grade
of ammonium sulfate contains 21 kgs available N but it does not contain P 2O5 and K2O. The remaining 79 kgs
 30
represents the materials termed as “carriers” or “fillers”. A mixed complete fertilizer with a grade of 12-24-12
contains 12% N, 24% available P2O5 and 12% K2O.

The fertilizer recommendation is expressed in kilograms N, kilograms P2O5 and kilograms K 2O per
hectare, respectively. In technical publications, this is written as, for example, 90-60-30. This recommendation
involves the application of 90 kgs N, 60 kgs P2O5 and 30 kgs K2O per hectare, respectively.

To calculate the weight of fertilizer, use the formula below.

Weight of fertilizer material = weight of nutrient required x 100

nutrient content in %

The weight of the nutrient required comes from the fertilizer recommendation, while the nutrient content
comes from the grade or analysis of the fertilizer material.

REFERENCES

Acquaah, G. 2002. Principles of Crop Production: theory, techniques, and technology. Pearson Education, Inc.,
New Jersey, U.S.A.

Bautista, O. (ed).1994. Introduction to Tropical Horticulture. SEAMEO-SEARCA and UPLB, Laguna.

PCARRD. 1982. Philippines Recommends for Soil Fertility Management. Los Baños, Laguna.

Horne, James and Maura McDermott. 2001. The Next Green Revolution: Essential Steps to a Healthy
Sustainable Agriculture. Food Products Press, New York, USA.

Villegas, L. (Undated). Fertilizer. Mimeographed. IRRI Cropping Systems Training Program.. IRRI, Los Baños,
Laguna.
 31
UNIT VI

PEST MANAGEMENT

By

Pedrito S. Nitural

Introduction

Pest management is one of the most important components of crop production. Crop losses from weeds,
insect diseases, and rats are often very significant. To minimize these losses, chemical crop protection products
developed and tested through research are increasingly made available and put into use in most agricultural
production systems. However, where the cost of chemical control is prohibitive, cultural practices designed and
modified to suit each specific crop needs are alternately adapted. Biological control through careful introduction
of parasites and predators is another attractive control method, especially for insect pests having acquired
immunity to a number of pesticides.

Among the abovementioned causes for crop failures, the weed group poses the greatest problem. These
unwanted plants offer the best competition with the growing crop, depriving them of their proper requirement for
light, carbon dioxide, water and nutrients from the soil. If left unchecked, the growing crop is eventually put to
a disadvantage, hence reduced yield. The group of chemicals specifically formulated to control weed population
are known as herbicides. Applied as pre-emergence, they effectively inhibit the germination of weed seeds in the
field. Herbicides applied as post-emergence can either be contact or translocated, the former inducing tissue
damage only at the point of chemical contact, while in the latter, evidence of damage is extensive. The crucial
point to consider regarding chemical weed control is selectivity or non-selectivity of herbicides. Because of this
property, acknowledge of weed biology becomes a requisite to a successful control.

Insect pests rank nest in causing major damage to crops and their control is largely dependent upon the
use of pesticides. Because of the environmental hazards associated with pesticides in addition to their prohibitive
costs, it is now felt to combine various compatible pest management methods that can insure plant protection at
a minimal cost. This approach calls for an integration of the biological and chemical measures into a single
unified pest control program.

The most commonly encountered plant diseases are caused by either fungi, bacteria or viruses. Since the
pathogens, e.g., fungi are intimate association with the host; any means of control seldom leave the crop
undamaged. Thus, any practical scheme of minimizing a disease outbreak would revolve around a program of
eliminating the infected plants followed by preventive spray with the recommended fungicides.

I. INSECT PESTS

WHAT IS A PEST?

Pest may be an organism which competes with limited resource, or is threatening man’s health or comfort and
possession.

WHEN DOES AN ORGANISM BECOME A PEST?

An organism becomes a pest when it begins to take what mankind wants.

Example:
1. by being introduce into, invading or otherwise entering on area previously uncolonized by the species.

2. A great and long lasting increase in numbers of a species take place.

3. There may be a change in an insect population.

 32

4. Changes in the activities and habits of people.

CAUSES OF OUTBREAK PESTS IN CROPS

1. large scale single crop culture – provide mass quantities of a specific food that may be desirable to a
certain species of insect
2. indiscriminate use of pesticides reduce the species diversity
3. the sensitive balance of insect and their natural enemies may be disrupted
4. favorable weather condition may contribute to increase pest population

MANAGEMENT OF PESTS

What are the Requirements for a Pest Management Decision Making?

1. Identification of the pests
2. An accurate measurement of pest population
3. An understanding of the pest habits and seasonal development
4. Assessment damage level
5. Assessment of potential ecological and environmental hazards that may occur with a proposed control
measures

The Economic of Pest Management

1. Economic injury level – the lowest pest population density that will cause economic damage
2. Economic threshold level – the pest population level at which controls are employed to prevent the
population from exceeding the economic injury level it is often referred to as an action threshold in
pest management
3. Equilibrium position - the average population level of an organism over a period of time.
Stable population – those population that remain close to their equilibrium position
Unstable population – those population that fluctuate widely.

Economic Classes of Insects

1. Occasional pests – those insect species that have very unstable population and under favorable condition
their numbers grow rapidly and exceed the economic injury level
2. Perennial pests – insects that have population nearly always exceed the economic injury level
3. Severe pests – pests that have equilibrium position above the economic injury level and always require
control interventions to prevent economic loss

Classification of Insect Control

1. Natural control – occurs when the forces of the nature reduce insect population. It includes the ff:
a. physical factors - e.g. temperature, moisture
b. biological factors - e.g. natural enemies
c. topographical factors - e.g. mountains, lakes as barriers
d. climatic factors

2.Applied control – any method used by man to suppress insect population to non-damaging levels.
These include:
a. legislative
b. physical
c. mechanical
d. biological
e. host resistance
f. genetic
g. cultural
h. chemical

A. Legislative – involves government action the state or federal legislature may place
 33
a quarantine on a pest prohibiting the movement of commodities. By law, the commodity can not be
shift out of the infested area without inspection or treatment.
B. Physical Control-involves the use of physical factors such as temperature, moisture, light sound ( mostly
done under controlled condition or green house)

1. Temperature-excessive heat and sometimes cold will eliminate insects and also insect pests of fruit in
storage since cold temperature inhibit insect development.
2. Moisture- essential to the survival of insects. Stored grain insects are controlled by storing dried grain with
low moisture content.
3. Light-can be used which will attract insect into trap where they killed.
4. Sound-can be used to confuse insects and attract them to a trap where they may be killed.

C. Mechanical Control-involves the use of mechanical devise such as mechanical barriers.

D. Cultural Control- utilizes cultural practices to alter the environment

so that it is unfavorable for a pest.
a. Sanitation- involves clean culture to eliminate weeds and volunteer plants upon which pest may
develop.
b. Tillage-may involved deep plowing to bury various stages of the pests so deeply they cannot emerge
shallow cultivation expose the pests to natural enemies and unfavorable weather.
c. Crop Rotation-use for insect control by substituting a crop which the insect cannot feed on and
develop.
d. Seeding-mgt. of seeding can be effective in preventing insect
infestation. Some problems can be avoided by planting early,
others by delayed planting while normal planting may solve
some problems.
e. Crop Fertilization-tolerance to pest attack can be increased
thru crop fertilization to promote vigorous plant growth.
f. Harvesting-harvesting is a measure frequently used to control
some insects.
g. Trap Crop-involve planting of an attractive crop early which
the pest would infest and could be destroyed before the crop
is planted.
h. Crop Site-selection of the crop site can be determining factor
in the development of a pest problem.

Biological Control

1. Biological Control-implies the manipulation of parasites,

predators and pathogens to manage the density of pest
population.

Parasitoids-insects that deposit their egg on or the host insects.

The hatching larva within the host insect killing when it competes
development.

Predators-consume their prey or host, may live on many indivi-

duals. A predator may be an insect bird, mammal or reptile.

Disease Pathogen-pathogen such a bacteria fungi, viruses and

microplasma kill insect by infection and producing disease.

Host Resistance-there are three mechanisms of resistance.

1. Antibiosis- a heritable characteristics of a plant which has an

adverse effect on the biology of an insect which causes mor-
tality, reduce fecundity reduce size or weight in ability to store
food reserve or other physiological abnormalities. This may due
to the chemical in a plant which interfere with normal physiolo-
gical functions of the pests or it may due to the morphological
 34
characteristics such as presence of hairs, spines, etc. that make
it unsuitable.

2. Antexinosis-term now use which was formerly called preference

or non-preference. The insect finds the plant unattractive
or has inherited avoidance behavior towards it.

3. Tolerance-the ability of the plant to sustain injury or recover to

increase growth and produce a crop in spite of insect attack.

Genetic Control

A. Alternation of Insect Fitness-mass rearing technique to introduce lethal genes altering the development
of an insect population.
B.Autocidal Control- to produce sterility
C.Genetic- manipulation of natural enemies.
D.Chemical Control-use when ever other measures have failed and
emergency intervention is necessary.

Classification of Chemicals According to their Mode of Action

1. Stomach Poison-kill the pest when ingested.

2. Contact Poison-kills the pest by absorption thru the body wall
3. Fumigants-this is gaseous which kill the pest by penetrating the
insect thru the trachea.
4. Attractants-utilizes the instinctive behavior of the pest insect
itself to regulate the pest population. Chemical are used to attract insect at site where they destroyed,
to divert insect in their search for mates or divert insect orientation.

5. Pheromones-are chemical which insect emit and respond to sex

pheromones attract the opposite sex of the same species. In some
cases, trigger flight or flight responses and other may mark a path
to a food source.
6. Allelochemicals-unlike pheromones, stimulates insects of another
species rather than those of the species producing chemicals.
7. Allomones-are allelochemicals which are defense secretion e.g.
toxin, in the larva of the monarch butterfly that make them unpala-
table to birds.
8. Kairomones-plant substances that emits odors which wants insects
by toxicity or attract them to right source of food.
9. Repellant-chemicals that are applied to prevent the damage by ren-
dering the commodity, animal or man unattractive, unpalatable, or
offensive.
10. Growth Regulators-the juvenile hormone which maintain the imma-
ture status or ecdysome regulate molting.

A. Causes of Outbreak of Insect Pests in Crops

1. Large scale single crop culture – provide mass quantities of a specific food
that may be desirable to a certain species of insect.

2. Indiscriminate use of pesticides reduce the species diversity

3. The sensitive balance of insect and their natural enemies may be

disrupted.

4. Favorable weather condition may contribute to increase pest population.

 35
B. Kinds of Damages Caused by Insects
1. Direct Damage – Those organisms which attack the marketable parts of the
crop.
Examples:
a.) Chewing the leaves, buds, stems, bark and fruits
of plants (adults and nymphs of grasshopper, larvae of Lepidoptera
b.) Sucking the sap from leaves, buds, stems and fruits (aphids, cotton stainer)
c.) Boring or tunneling in the bark, stems or twigs (borers); in fruits, nuts and seeds
(worms or weevils).
2. Indirect Damage – Those that attack the non-marketable parts of the crop
such as roots, stems, which causes the crop to lodge.
Examples:
a.) Causing cancerous growths on plants, within which they live and feed (gall
insects)
b.) Attacking roots and underground (subterranean or soil insects)
c.) Laying their eggs in some parts of the plant
d.) Taking parts of the plant for construction of nests or shelters
3. QuantitativeDamage-the actual destruction
of plant tissue,interruption of metabolism or commodity, injury which
result to less
yield or marketable product that occur in
the absence of pests.

Example- feeding of insects on the leaf

may cause reduction in photosynthesis
and subsequently reduce yield.

1. Loss in yield – reduction in yield is the first consideration of loss

from insect infestation
2. Lower plant tolerance – stress for insect infestation may hinder
recovery
3.Transmit diseases to plants – insect feeding on plants may not only
cause serious economic damage but may cause serious loss by
transmitting disease pathogen

4. Qualitative Damage – affects the physical shape, size and appearance

or nutritive composition of the product

Examples: 1. Loss in marketability of the commodities

2.Alter nutritional value of the product

3. Aesthetic value of the product is lost

II. PLANT DISEASES

Plant diseases constitute one of the natural hazards in crop production. Their outbreaks are often
the principal factors that alter production levels and imperil market schedules and consumer needs. Many
diseases can be controlled or prevented but some remain for the researchers to study and conquer. Control
measures for plant diseases are based upon correct diagnosis and understanding of the causal organism
(pathogen) attacking the host plant. Rapid and accurate diagnosis, close observation and interferences are
always useful in dealing with plant diseases.

The Economic Importance of Plant Diseases

Plant diseases cause enormous economic losses. Crop losses are expressed in various
ways. A common type of loss is the reduction in yield of diseases plants; Deterioration of harvested
produce during storage, marketing or transport; Reduction in the quality of produce; Poisonous
substances or toxins that endanger the health of the consumers; Causes the host plant to become
 36
weak and susceptible to attack by other pathogens; and, increase the costs of production and
handling.

Causes of Plant Diseases

The causes of plant diseases may be divided into two groups: non-parasitic and parasitic.
Non-parasitic diseases are due to either lack or excess of minerals, unfavorable soil-water relations
or other environmental factors such as air pollution, very low or very high temperature, etc.
Symptoms associated with non-parasitic diseases are frequently confused with those caused by
definite parasitic entities. In addition, injury from non-parasitic troubles often permits parasitic
pathogens such as fungi, bacteria, nematodes and viruses to enter and further damage the plant.

Parasitic diseases may be grouped according to the different causal organisms. These are
fungi, bacteria, viruses, mycoplasma, nematodes, and flowering parasitic plants.

Fungi. These are tiny, simple living plants commonly called molds. Since they are not
green in color, they lack the ability to photosynthesize or produce their own food. They depend
upon living host plants for their nutrition. They are therefore called parasites and in the course of
feeding, such parasites produce diseases on their host plants.

Bacteria. Bacteria are considered the simplest of plants. They are tiny, consisting of only
one cell, and multiply by cell division as frequently as every 10-15 minutes. Like fungi, bacteria
lack green pigments and hence cannot produce their own food. There are many kinds of bacteria
capable of feeding on and producing a disease condition in higher plants.

Bacteria affect plants in various ways and their symptoms may be expressed as galls, wilts,
leaf spots, soft rots, streaks, and blights.

Viruses. Viruses are infectious particles that attack many forms of life inducing bacteria
and plants. They are so tiny that they cannot be seen with an ordinary microscope but only with
the aid of an electron microscope. Symptoms of virus diseases on plants vary. The common
symptoms and effects are stunting, yellowing, curling, mottling, and overgrowths. Some plant
viruses are very infectious and can be transmitted easily from diseased to healthy plants by mere
contact between plants or by animals, man and machines. Others are spread only be feeding and
plant-to-plant movements of insects, by asexual propagation of virus infected planting stocks, or
through virus-infected seeds.

Nematodes. Plant-parasitic nematodes are active, slender, thread-like roundworms, about

1/70 of an inch long. Their mouth part is equipped with a tiny spear or stylet which they use to
puncture plant cells to obtain plant juices. A number of plant parasitic nematodes feed from the
outside of the roots, stems, buds, and leaves; others feed by tunneling through the roots. Their
feeding causes abnormal swelling or galling of the root. (This uneven swelling should not be
confused with root nodules on legumes caused by beneficial nitrogen-fixing bacteria). Plants
attacked by nematodes lack vigor. In most cases, nematode-damaged plants become more
susceptible to other diseases. Nematodes can be controlled by chemical means.

Parasitic Flowering Plants. These are seed plants that grow on trees, garden plants, and
field crops. They obtain all their food materials and water from the host plants through tiny sucker-
like structures at points of contact with the host. These sucker-like or root-like outgrowths force
their way into the water and food-conducting tissues of the host plants. Mistletoe and “bunga ng
tubo” are the common parasitic flowering plants found in the Philippines.

Mycoplasma. It has been demonstrated that several “yellow diseases” believed to be

caused by viruses were due, in fact, to a group of tiny organisms whose sizes are between those of
the virus and bacteria. These organisms, called mycoplasmas (meaning, “fungus” form), have no
rigid cell walls but can assume many shapes because of their fragile membranes. They can be seen
under the electron microscope as elongated branching filaments which later break up into round
cells. Majority of the mycoplasma diseases are transmitted in nature by leaf hoppers.
 37

Symptoms of Plant Diseases

Symptoms are the expression by the suscept or host of a pathogenic condition by which a
particular plant disease may be distinguished from other diseases. The term symptom however,
sometimes take a broader meaning to include any measurable host response to infection such as
increased respiration and increase leaf temperature.

Symptoms have been variously described as primary or secondary, localized or systematic,

and histological or morphological.

Primary symptoms are those that are the immediate and direct results of the usual agent’s
activities on the invaded tissues whereas secondary symptoms are the effects on the distant and
uninvaded plant parts.

Localized symptoms is essentially internal, and seen only upon the dissection of the
diseased planbt portion and examination under the microscope. It is expressed as an abnormality
in cell content, structure or arrangement. Cell enlargement and vascular discoloration are
histological symptoms. Morphological symptoms are those malformations and other changes that
are visible to the naked eye.

Symptoms are generally classified into (a) necrotic symptoms, (b) hypoplastic symptoms,
(c) hyperplastic symptoms. Necrotic symptoms involve the death of protoplast, cells or tissues.
Examples are spot, blight, scorch, canker, and die-back. Beforre the actual death of the protoplast
or cell some eveidences of protoplasmic disorganization and degeneration may appear. Examples
of these plesionecrotic symptoms are silvering, yellowing and wilting.

Hypoplastic symptoms appear when there is an inhibition or failure in the differentiation

or development of some aspect of plant growth. Stunting, chlorosis, mottle, mosaic, curling and
resetting are examples of hypoplastic symptoms.

Hyperplastic symptoms are expressed with the occurrence of excessive multiplication:

enlargement or overdevelopment of plant organs including the abnormal prolonged retention of
the green color. Gall formation, fasciation, scab, premature defoliation of fruit drop, and greening
are examples of hyperplastic symptoms.

The various symptoms were categorized by Kenaga (1974) into (a) abnormal coloration,
(b) wilting, (c) death of host tissue, (d) defoliation and fruit drop, (e) abnormal growth increase of
host, (f) stunting, and (g) replacement of host tissue.

Specific symptoms and their descriptions are given below.

Etiolation – yellowing of normally green tissues caused by inadequate light.
Chlorosis – yellowing caused by some factor other than light, such as a virus or a mycoplasma.
Mosaic – the presence usually on leaves of variegated pattern of green and yellow shades with
sharply defined borders.
Mottling – the variegated is less defined than ,mosaic and the boundaries of light and dark
variegated areas are more diffused.
Veinclearing – the veins are transluscent or pale while the rest of the leaf is its normal color.
Wilting – may be due to an infectious agent or to lack of water. Wilting caused by the latter is
often temporary and the plant recovers upon the application of enough moisture unless the
drought is prolonged and the plant dies. Wilting by an infections agent often leads to, death
of the plant unless controlled in time.
Rotting – is the disintegration and decomposition of host tissue. A dry rot is a firm, dry decay
whereas a soft rot is a soft, watery decomposition. Any plant part may suffer from rot such
as fruit rot, stem-end rot, blossom-end rot, stalk rot, root rot..
Spot – a localized nercotic areas referred to as a lesion. Individual spots may be circular,
angular or irregularly shaped. Several spots may run together or coalesce forming large
nercotic areas.
Blight – an extensive, usually sudden, death of host tissue, such as leaf blight.
Shot-hole – a perforated appearance of a leaf as the dead areas of local lesions drop out.
 38
Canker – an often sunken nercotic area with the cracked border that may appear in leaves,
fruits, stems and branches.
Mummification – an infected fruit is converted to a hard, dry, shriveled mummy.
Leak – the host’s juices exude or leak out from soft-rotted portions.
Die-back – a drying backward from the tip of twigs or branches.
Pitting – definite depressions or pits are found on the surface of fruits, tubers and other fleshly
organs resulting in a pocked appearance.
Rosetting – shortening of the internodes of shoots and stems forming a crowding of the foliage
in a rosette.
Abscission – premature falling of leaves, fruits of flowers due to the early laying down of the
absciss layer.
Phyllody – metamorphosis of sepals, petals, stamens or carpels into leaf-like structures.
Curing – abnormal bending or curling of leaves caused by overgrowth on one side of the leaf
or localized growth in certain portions.
Scab – slightly raised, rough, ulcer-like lesions due to the over-growth of epidermal and
cortical tissues accompanied with rupturing and suberization of cell walls.
Damping-off – rotting of seedlings prior to emrgence or rotting of seedling stems at an area
just above the soil.
Sarcody – abnormal swelling of the bark above wounds due to the accumulation of elaborated
food materials.
Callus – an overgrowth of tissue formed in response to injury in an effort of the plant to heal
the wound.
Fasciculation or fascination – clustering of roots, flowers, fruits, or twigs around a common
focus.
Blast – term applied to the sudden of young buds, inflorescence or young fruits.
Russeting – a superficial brownish roughening of the skin or fruits, tubers or other fleshy
organs usually due to the suberization of epidermal or sub epidermal tissues following
injury to epidermis.
Streak or stripe – long, narrow nercotic lesions on leaves or stems.

Signs of Plant Diseases

Signs of plant disease refer to the structures of the pathogen that are found associated with
the infected plant. Examples sign are fungal mycelia, spores and fruiting bodies, bacterial ooze,
sclerotial bodies, nematodes at various growth stages and plant parts of phanerogams (parasitic
flowering plants).

Classifications of Plant Diseases

• Classification according to the affected plant organ such as root diseases, foliage diseases, fruit
diseases and stem diseases. This can be related to the physiological processes affected as root
diseases affect water and mineral uptake; leaf diseases affect photosynthesis; fruit diseases
affect reproduction; stem diseases affect water conduction, etc.
• Classification according to the symptoms such as leaf spots, rusts, smuts, anthracnose, mosaics,
wilts, fruit rots, etc.
• Classification according to the type of affected plants such as vegetable diseases, disease of
forest trees, diseases of field crops, diseases of ornamental, etc.
• Classifications according to the type of pathogen that causes the disease. These may be
grouped into infectious diseases such as: (a) diseases caused by fungi, (b) diseases caused by
mycoplasmas, (c)diseases caused by bacteria, (d) diseases caused by viruses, (e) diseases
caused by viroids, (f) diseases caused by protozoa, (g) diseases caused by parasitic flowering
plants and (h) diseases caused by nematodes; and into non-infectious diseases caused by non-
parasitic or abiotic agents such as (a) extremely high or excessively low temperatures, (b)
unfavorable oxygen relations, (c) unfavorable moisture conditions, (d) nutrient deficiencies,
(e) mineral toxicities, (f) air pollution, (g) toxicity of pesticides, etc.

Control of Plant Diseases

The adoption of control measures in checking plant diseases is based on an understanding

of the cause, the pathogen’s life cycle, time of infection, parts involved, how the disease agent is
distributed, and also upon cost. In practice, the application of control methods may be directed
 39
towards: 1) the causal agent and 2) the plant. These measures may be carried out through one
or more of the following practices:

1. Selection and planting or resistant and adapted varieties

2. The use of disease-free seeds or planting stocks
3. Application of protective or eradicative fungicides
4. Planting in a well-prepared, fertile, well-drained field or lot
5. Crop rotation
6. Soil sterilization
7. Change in a cropping practice
8. Weed and insect control
9. Quarantine
10. Biological control (anti-bioses)

However, it is important to consider the cost of the treatment. It is not practical to suggest
control measures if the requirements of time, labor and materials involved in the treatment are such
that the gain to the grower will not be greater than the cost of the measures adopted.

Signs and Plant Diseases

Signs and plant diseases refer to the structures of the pathogen

that are found associated with the infected plant. Examples: sign are
fungal mycelia, spores, and fruiting bodies, bacterial ooze, sclerotial
bodies, nematodes at various growth stages and plant parts of phane-
rogams ( parasitic flowering plants ).

Plant Disease Diagnosis

Diagnosis is the identification of specific plant diseases through

their characteristics symptoms and signs including other factors that
may be related to the disease process. Correct plant disease diagnosis
is necessary for recommending the appropriate control measures, and
in plant disease surveys.

Studies and work that require actual proof of pathogenicity require

that Koch’s postulate are applied, i.e. 910 The suspected pathogen must always be present in the plant when
the disease occurs,(2)The organism which is believed to cause the disease must be isolated and
grown in pure culture, (3)The pure culture of the organism must produce the symptoms and signs of the
disease when inculated into a
healthy plant and (4) The suspected causal organism must be reisolated in pure culture from the inoculated
plant and must be identical to the
original organism.

Modifications of Koch’s rules of proof should be made when dealing with obligate parasites that cannot
be grown in pure cultures, such as the viruses and nematodes, as well as when working with abiotic or non-
living disease agents.

Classifications of Plant Disease

Classification according to the affected plant organ such as

Root diseases, foliage diseases, fruit diseases and stem diseases. This can be related to the
physiological processes affected as root diseases affect water and mineral uptake; leaf diseases
affect photosynthesis; fruit diseases affect reproduction; stem diseases affect water
conduction, etc.

Classification according to the symptoms such as leaf spots, rusts, smuts, anthracnose,
mosaics; wilts, fruit rots, etc.
 40

Classification according to the type of affected plants such as vegetable diseases, diseases of
forest trees, diseases of filed crops, diseases of ornamental, etc.

Classifications according to the type of pathogen that causes the disease. These may be
grouped into infectious diseases such as: (a) diseases caused by fungi, (b) diseases caused by
mycroplasmas, (c) diseases caused by bacteria,(d) diseases caused by viruses,(e) diseases
caused by viroids, (f) diseases caused by protozo, (g) diseases caused by parasitic flowering
plant and (h) diseases cause by nematodes; and into non-infectious diseases caused by non-
parasitic or abiotic agents such as (a) extremely high or excessively low temperatures, (b)
unfavorable oxygen relations,(c) unfavorable moisture conditions, (d) nutrient deficiencies,
(e) mineral toxicities,
(f) air pollution, (g) toxicity of pesticides etc.

Non-parasitic Agents of Plants Disease

The non-parasitic agents of disease are characteristically non-living and therefore are not
spread from diseased to healthy plants.The diseases that they cause are non-infectious .
Diseases caused by non-parasitic agents have been also referred to as physiological disorders.
Non-infectious disease are recognized by their symptoms ( no signs are present, of course). A
knowledge of the soil conditions, temperature ranges, the weather immediately before and
during disease occurrence, and other environmental factors are often necessary for correct
diagnosis.

The control of these is by avoiding, whenever possible, the causal environmental factor such as
chemical, excessive sunlight, etc. Some may be controlled by providing the lacking factor as
in nutrient deficiency diseases, and disease caused by inadequate moisture, acidic soil, etc.

The more common non-parasitic causes of diseases in plants are:

-Excessively low temperatures

-Temperatures that are too high
-Lack of oxygen
-Too much or too little light
-Adverse meteorological conditions
-Air pollutants
-Mineral deficiencies
-Mineral excesses
-Unfavorable soil Ph
-Excessive pesticide levels
-Improper agricultural practice
-Lack or excess of soil moisture
-Naturally occurring toxic chemicals

Weeds and their Control

Definition of weed. The term “weed” has been defined in various ways, the most
common of which are:

A weed is a plant growing “out-of-place”

A weed is a plant growing where it is not desired, useless, unwanted and
undesirable
A weed is a plant that interferes with man or area of his interest

A. Classification of Weeds.
 41
Because of their diversity in morphology, habit and adaptation, weeds cannot be classified
satisfactorily using only one category. Thus, weeds may be classified according to growth habit
(vines, shrubs, trees), life span (annual, biennial, perennial), body texture (herbaceous, woody),
and habitat (terrestrial, epiphytic, aquatic). The aquatic weeds are further subdivided into
emergent (when the upper portion is above water but roots are anchored to the ground),
submerged (when all parts are under water), and floating (when the upper portion is above water
but roots are not anchored to the ground). In weed control research, weeds are more conveniently
classified according to their gross morphology a grasses, broadleaf weeds and sedges.

1. Grasses
Grasses are members of the family Graminae which range from small, twisted, erect, or
creeping annuals and perennials. The stems are called culms with well-defined nodes and
internodes. Leaves arise alternately in two rows from the nodes. The leaf is composed of two
parts, the leaf sheath which clasps the stem with the margins overlapping to form the tube, and
the leaf blade which is usually thin, narrow and the linear with parallel venation. At the junction
of the leaf blade and the leaf sheath is often found a membranous, often hairy outgrowth called
ligule. Example of grasses are Rottboellia cochinchinensis and Echinochlea colona.

2. Sedges
Sedges are members of the family Cyperaceae. They bear a close resemblance to grasses
and can be distinguished by a thin triangular stem, absence of a ligule, and fusion of leaf sheaths
forming a tube around the stem. Perennial sedges have underground tubers and/or rhizomes.
Examples of sedges are Cyperus rotundus and Fimbristylis litteralis.

3. Broadleaves
Broadlef weeds are those belonging to other families of Monocotyledonae and
Dicotyledonae. They are identified by their fully expanded, broadleaf structure with netted
venation. Examples of broadleaf weeds are Monochoria vaginalis, Amaranthus spinosus, and
Spomoea triloba.

B. Damages Caused by Weeds.

Weeds cause considerable yield losses in most field crops because they compete for light,
water, carbon dioxide and soil nutrients with these crops. Indirectly, weeds reduce production
by serving as alternate hosts for diseases and such insects as leafhoppers and stem borers. These
may eventually infect and infest the crops, respectively. Weeds also reduce the quality of
harvested grain, clog irrigation and drainage canals and increase labor cost.

Many weed species that are commonly found in upland and lowland areas in the Philippines
serve as hosts of insect pests and plant pathogens. For example, common purslane (Portulaca
oleracea) and tropic ageratum (Ageratum conyzoides) have found to serve as hosts for root-knot
nematodes. It has also been reported that horse purslane (Trianthema portulacastrum) and spiny
amaranth (Amaranthus spinosus) are hosts of tobacco mosaic virus while jungle rice
(Echinochlea colona) is a host of rice leaf-whorl maggot.

C. Critical Period of Weed Competition.

Field crops and weeds compete with each other in varying degrees. In crop production, it
is necessary that the crop plants be the dominant competitors so that most of the environmental
potentials for production are available for them.

Studies on crop-weed competition have shown that there is a period in crop growth when
weed competition is most damaging. The results of many studies have indicated that most of the
injury to crops caused by weeds occur during the first 25-30% of their life duration. This is
called the critical period of weed competition and is the most appropriate time to apply control
measures. Weeds that emerge after the critical period of weed competition no longer reduce
crop yield significantly. By this time, the crops have already developed extensive root systems
and considerable foliage to compete favorably with the late-emerging weeds.
 42

D. Methods of Weed Control.

Methods of chemical control include mechanical, physical, biological, and chemical.

1. Mechanical control.

This is usually done by hand-pulling or with the use of handtools like hoe, shovel, scythe, or
with the use of tractor-driven tools like harrow, disc plow, rotary weeder and mower.

2. Physical control

Fire is used to control weeds in areas like ditches, roadsides and other waste areas; to
remove underbrush and broadeaf species; and for annual weed control. Burning must be repeated
at frequent intervals to control perennial weeds. Water is usually used in the control of weeds
in lowland rice areas through flooding. On the other hand, smothering by mulching using straw,
hay, plastic, and other materials, is also used effectively in some cases.

3. Biological control

In this method, “natural enemy” of the weed is used which is harmless to the desired plants.
The natural enemy may be insect, disease organism, parasitic plant, selective grazing by
livestock and by using competitive crop cultivars. An example of biological weed control in
Hawaii uses various species of moths to control the throny shrub (Lantana camara) by eating
the flowers and leaves of the weed species.

4.Chemical control

This method involves the use of organic and inorganic chemicals (herbicides or
weedicides) to control weeds. Herbicides are classified into three categories based on their time
of application. These are pre-planting, pre-emergence, and post-emergence. Pre-planting
herbicides may be applied or incorporated into the soil prior to planting the crop. Pre-emergence
herbicides are applied prior to the emergence of either or both the crop and the weeds. Post-
emergence herbicides are applied after the emergence of either or both the crop and the weeds.
Often, the chemicals are applied post-emergence to the crop but pre-emergence to the weeds.

IV. RODENTS AND THEIR CONTROL

Rats are among the major pests known the world over. Large areas

of agricultural crops which include coconut, rice, corn, are destroyed or seriously damaged by
them every year. Their number varies from locality to locality, depending not only on the climatic
conditions, but also on the efficiency of control measures and the availability of scientific resources
necessary to implement a successful rat control program. Many people do not realize that a small
rodent population can, in time, cause serious damage to crops if control measures are not instituted.

A. Determination of Rat Population in a Given Area.

Several methods have been used to estimate rodent population in a given area. These
methods include observations of animal signs such as burrows, droppings, and food consumption
(damage to crop). These methods can more or less supply the general information on the relative
rat population in the area.
 43
B. Methods of Rat Control

Rodents can be controlled by using chemical control, mechanical or physical control,

regularly control, and cultural control.

1. Chemical Control.
Chemical control of rats may be carried using: a) acute toxicants like sodium fluoro-acetate
and thallium sulfate, b) chronic toxicants which act as anticoagulants, like warfarin, coumatetralyl,
chlorophacinone and diaphacinone, c) fumigants, for rats occupying burrows, like hydrogen
cyanide, methyl bromide, aluminum phosphide, d) chemosterilants which are reproduction
inhibitors, e) attractants and f) repellants like nicotine sulfate, lime sulfur, sodium silicofluoride.

2. Mechanical or Physical Control.

This may be done by: a) the blanket system where a field of about 1/8 to ¼ hectare is circled
by men who move toward the center and catch the rats along the way, and b) trapping using live
traps and snap traps.

3. Regulatory Control.

Several quarantine or restrictive measures have been promulgated and implemented to

exclude rats from foreign sources. Some of these measures are rat guards on connection lines of
vessels, rat inspection of vessels, fumigation of vessels, etc.

4. Control by Cultural Methods.

This refers to reducing rat population by means of regular farm operations designed to
destroy or prevent them from causing damage. Clean culture, sanitation and removal of trash
from the fields will help in controlling rats.

Definition of Terms

Predator – an organism which lives by preying upon animals.

Predatory Insect – an insect that feeds on another insect.

Pupa - an inactive stage in the life cycle of some insects between the larva and the adult and
during which time the insect is usually in a case or cocoon.

Quarantine - control of import and export of plants/animals to prevent spread of pests and
diseases.

Resistant - possessing qualities that hinder the development of a given pathogen.

Rodenticide – a chemical compound used to kill rats or rodents.

Rosette – short, bunchy habit of plant growth.

Rot – the softening, discoloration and often disintegrating of a succulent plant as a result of
fungal or bacterial infection.

Rust – a disease giving a “rusty” appearance to a plant and caused by one of the Uredinales (rust
fungi).

Scavenger Insect – insect that feeds on decayed plants and animals.

Sign – an expression of the organism causing the disease.

Sterilization – the elimination of pathogens from the soil by means of heat or chemicals.
 44
Suscept – any plant that can be attacked by a given pathogen; a host plant.

Symptom – the external and internal reactions or alterations of a plant as a result of a disease; an
expression of the host plant against a disease.

Tolerance – the ability of a plant to sustain the effects of a disease without dying or suffering
serious or crop loss.

Vector – an animal able to transmit a pathogen.

Virus – a sub-microscopic obligate parasite consisting of nuclei acid and protein.

Viricide – a chemical agent used to destroy virus.

Weedicide – (see Herbicide)

Wilt – loss of rigidity and drooping of plant parts generally caused by insufficient water in the
plant.

References

1. Annual Report. 1970. Rodent Research Center. College, Laguna, Philippines.

2. Agrios, G. N. 1969. Plant Pathology. Academic Press, Inc. New York, U.S.A.

3. Bautista, O.K. and R. C. Mabesa. 1977. Vegetable Production. UPLB-CA, College, Laguna,
Philippines.

4. Borrer, D. J. and D. M. De Long. 1964. Introduction to the Study of Insects. 4 th ed. Holt, Rinehart
and Winston, New York, U.S. A.

5. BPI-AID. 1977. Community Rat Control. Pamphlet. 18 pp.

6. Gallego, V. C. and R. G. Abad. 1977. Rats and their Control. (mimeo).Crop Protection Div.
Philippine Coconut Authority, Agricultural Research Branch.

7. Little, V.A. 1972. General and Applied Entomology. 3rd ed. Hayer and Row Publishers, New
York, U. S. A.

8. Luckman, w. A. and R. L. Metcalf. 1975. Introduction to Insect Pest Management. John Wiley
and Sons, New York, U. S. A.

9. Mercado, B. L. 1979. Introduction to Weed Science. SEARCA, College, Laguna, Philippines.

10. Metcalf, C. L. and W. P. Flint. 1967. Destructive and Useful Insects. 4 th ed. McGraw-Hill
Publishing Co., Ltd., New York.

11. Raros, L. C. and S. G. Reyes. 1980. Laboratory Manual and Compilation of Keys for Insect
Taxonomy. UPLB-CA, College, Laguna.

12. Rice Production Manual. 1970. UPCA, College, Laguna.