Crop propagation
Crop propagation is the reproduction of a new plant as an independent unit. It is the creation of new plants from
parent ones.
Methods of propagation
1. By seed (sexual propagation)
2. By vegetative organs (asexual propagation)
Sexual propagation of crops: It is the production of new plants through the use of seeds.
Sexual propagation of crops involves fertilization, that is union or joining together of male and female gametes
(pollen grains and ovules) from two parents’ flowers to from the ovule which later mature to produce seeds.
Seeds are the main plant form of reproduction in the sexual propagation of crops.
Characteristics of a good seed
1. Highly viable – containing living cotyledon or endosperm.
2. Good and robust shape and size.
3. Early maturing – ability to grow and reach a market size at a fast rate.
4. Free from pest attack.
5. Well-filled and free from holes.
6. High yield – has the prospect to generate higher income or profit
7. Hardiness – drought, pest, and disease resistance.
Examples of sexually propagated crops that are sown directly in the field:
Maize, sorghum, melon, cowpea, groundnut, soya beans, okra, millet, cotton, etc.
Examples of sexually propagated crops that are first raised in the nursery for some time and later
transplanted into the field are cocoa, pepper, onion, oil palm, citrus, tomato, rice, etc.
Asexual propagation of crops: Asexual propagation is the reproduction of new plants from the parent
plant through the use of vegetative organs/parts such as the leaves, stems, roots. This method does not make use
of seeds. It is reproduction through the plant parts since these parts can obviously grow again i.e. regeneration.
The propagation in a sexual plant can be done by planting some parts of the plants like stems, roots and leaves.
Forms of asexual propagation
A. Cutting: This is the method in which part of the growing plant is cut and placed in moist soil or water. This is
most common among tuber crops that are propagated through their roots or branches. Hardwood cuttings are
prepared from the stem of a perennial plant taken from the previous season’s growth. These cuttings may be
from 15 – 30cm long depending on the plant variety. Examples of plants propagated by cutting are cassava,
hibiscus, sugar cane, cocoa, kola, and coffee, while softwood cutting is obtained from sweet potatoes.
B. Grafting: This is a method in which one part of a plant is inserted into another plant in a way that they
will unite and continue to grow as one plant. This is common among tree crops in which the parts of the
plant brought to be grafted are called the scion while the part firmly attached to the soil is called the
stock. Grafting brings into close contact with the vascular cambia of both the scion and the stock. As in
budding, both the scion and the stock must be closely related to avoiding incompatibility which could
result in the breaking of the scion from the stock at a later date. An example of a crop easily propagated
by grafting is orange (citrus).
C. Budding: This is the union of a bud with a stock. Budding is similar to grafting. The difference is that the
bud is used instead. The bud is the scion and the plant prepared to receive it is called the stock. Under this
method, a well-developed bud from a disease-free plant.
D. Layering: Layering is a technique of plant propagation where the new plant remains at least partially
attached to the mother plant while forming new roots and can occur naturally through modified stem
structures. It is a means of plant propagation, in which a portion of an aerial stem grows roots while still
attached to the parent plant and then detaches as an independent plant.
E. Marcotting: Marcotting, also known as air-layering, is a way of getting clones of woody plants that are
often difficult to root from cuttings. This method involves propagating a new plant from a branch still
attached to the parent plant, by getting roots to form on the branch. It is quite similar to layering; the
difference is that while layering is done in the soil, marcotting is done in the air, hence the name air-
layering. In both cases, the stem is encouraged to develop roots before it is detached and planted
separately as a new plant.
F. Division: Division is a simple means of vegetative propagation for plants that produce suckers, stolons,
bulbs, tubers, or rhizomes. To propagate by division, dig up the plant and divide it carefully using some
spade or secateurs. The division is the easiest form of vegetative propagation. It involves digging up and
severing a portion of the root system of a plant and replanting it. Depending on the plant species and age,
one to twenty divisions may be made from one plant.
In summary, Cuttings involve rooting a severed piece of the parent plant; layering and marcotting involve
rooting a part of the parent and then severing it; Division involves digging up and severing a portion of the
root system of a plant and replanting it. Budding and grafting involve joining two plant parts from different
varieties.
Advantages of sexual propagation
1. Seeds are cheap to obtain
2. Seeds are small and therefore convenient to handle, store and transport
3. Seeds can be stored for long periods
4. When seeds are stored in cool dry places, they can remain viable for at least one planting season.
5. Crop population increase can easily be obtained through the use of seeds.
Disadvantages of sexual propagation
1. Some seeds produce plants that do not resemble their parent plants
2. Some seeds produce low yields during the first year
3. Plants grown from seeds are not always uniform in growth, maturity, yield, and other characteristics.
4. Plants grown from take a longer time to mature and produce fruits
Advantages of asexual propagation
1. Plants are true to type and uniform in quality, growth habit, and yield
2. All plants propagated at the same time by vegetative means start bearing at almost the same time.
3. It is the only way of propagation for plants that cannot produce seeds.
4. Plants mature and start bearing fruits early
5. A plant that is susceptible to certain soil conditions can be grafted onto a rootstock that is resistant to
these conditions.
Disadvantages of asexual propagation
1. Plants are not usually very vigorous and therefore do not live long enough
2. It is not possible to produce new varieties of plants.
3. Budding and grafting require special skills
4. Viral diseases can be transmitted to new plants
Cultural practices
Cultural practices in agriculture are all the activities carried out on the farm before, during, and after the planting
of the crop.
Pre-planting operations
These are operations carried out before sowing. They include choosing of site, clearing, stumping, plotting,
ploughing, harrowing, and ridging.
These are the farming operations carried out before planting is done. These activities are carried out to prepare
and make the soil conducive for the crop to be planted. Pre-planting operations in sequence are: the selection of
the site, surveying of the soil and land measurement, clearing, stumping, field plotting or farm layout, tilling or
ridging, ploughing, harrowing nursery, and nursery practices.
Planting operations
This is the actual planting of the seedlings, seeds, or propagation materials. Planting operations comprise all
activities carried out during the planting process. They include the following:
Seed treatment – This is a way of dressing the seeds or the planting materials, to adequately prepare them for
planting, so as to ensure good germination or sprouting, and subsequently good yield.
Spacing and planting – Spacing refers to the planting distance allowable for each crop species, between inter-
row and intra-row plants. It varies from one plant species to another. Incorrect spacing may lead to over-
crowding, resulting in competition for light, water space, soil nutrient, etc.
Seed rate – This is the quantity of seeds or planting materials required to plant up an area indicated in the amount
of seed per stand to the field.
Planting date – This varies with crops, species and climatic factors. However, there is early planting between
March and May and late planting from August to October.
Planting depth – This is the sowing depth required or allowed for the plant to perform well in the field.
Transplanting – this is the process of removing the seedling from the nursery to the field, where they will be
allowed to establish until maturity and harvesting.
Prickling – This is the removal of seedlings at two-leaf from pre-nursery to nursery.
Post-planting operations
These are activities that are carried out after the crops are planted or transplanted up to the time of harvesting. A
good post-planting operation is insurance against crop failure and good follow-up activities. These operations
include the following:
Thinning – This is the removal of weak, dead, or excess plants/seedlings, so as to enable the better-established
and healthy ones to develop properly.
Supplying – This is the replacement of dead seedlings with other planting materials, so as not to allow the
creation of unnecessary spaces.
Mulching – This involves the use of mulch materials like dry grasses, wood shavings, straw, etc. to cover the soil
surface, so as to prevent or reduce the loss of soil water by evaporation, prevent the growth of weeds, regulate soil
temperature and add organic manure to the soil.
Manuring/Fertilizer application – Adequate supply of nutrients is required by plants for growth and increased
yield. This is achieved by incorporating organic manure and inorganic fertilizers into the soil.
Harvesting – This is the act of collecting mature crop products from the field, either for immediate consumption,
processing, marketing or storage. This is done either manually by hand-picking or by use of mechanical means
like simple harvesters, mechanical reapers, etc. Harvesting implement includes sickle, cutlass, go-to-hell, etc.
Staking, weeding, pruning/trimming, pest, and disease control – Are also aspects of post-planting operations.
In staking, plants with trailing stems are supported with stakes so as to allow them to grow well, get exposed to
enough sunlight, and be free from soil-pest attacks, etc. Plants with weak stems are propped to provide support.
During weeding, unwanted plants are removed to avoid competition with crops for food, water, light, space, etc.
Post-harvest operations
These are activities carried out after harvesting have been done. The activities in this category include farm-level
processing, storage, assembling, branding, grading, distribution, marketing, etc.
Farm-level processing is a series of activities used in converting harvested farm produce into clean and
marketable forms. After harvesting, crops need to be processed so that they can be consumed or stored for future
use. Methods of processing include shelling, de-husking, peeling, winnowing, etc.
Harvested crops not meant for immediate sale or consumption would have to be stored properly. Grains yielded
are stored in granaries or bins at go-downs for later use or marketing. Therefore, methods of crop protection need
to be better. In order to protect grains from pests and rodents, cleaning, drying, fumigation, etc. are done prior to
storing.
Effects of timely harvesting versus late harvesting
Harvesting is the removal and gathering of mature crops for processing and storage. The sign of maturity differs
for different crops. For crops like yam, cocoyam, and groundnut, maturity is signified when most of their leaves
are turning yellow and dry. The purpose of production also affects the maturity, the stage at which the crop is to
be used. For example, maize meant to be eaten fresh is generally harvested green while that meant for storage is
harvested dried.
The effects of late harvesting include the following:
-Crops may overripe and become wasted
-Birds, rodents, and other pests may feed on the mature crops thereby wasting them
-Diseases may meet the crops in the field if not harvested on time.
