PRACTICAL NO.

1
SELECTION OF SUITABLE LOCATIONS FOR CROP FARMING UNDER DRY
ZONE CONDITIONS

Factors to be considered

1. Topography
i. Landform – Undulating.
ii. Land slope range 0– 8%
2. Soil
i. Soil Type – Reddish Brown Earth (RBE) and Low Humic Gley (LHG)
ii. Soil texture – Sandy loam to Sandy clay loam
iii. Seepage and Percolation – RBE 7–10 mm/day, LHG 3–4 mm/day
3. Drainage conditions
i. Drainage Classes – Well Drained, Moderately Drained (or Imperfectly Drained), and
Poorly Drained.
4. Climate
i. Rainfall amount and distribution - 1400 mm approximately, bimodal pattern, two seasons
Yala - March to August (First Inter Monsoon (FIM) and South-West monsoon (SWM))

Maha - September to February (Second Inter Monsoon (SIM) and North-East Monsoon
(NEM))

ii. Potential evapotranspiration (PET) = 3 – 5.5 mm/day

5. Water
i. Type of source – Direct rainfall, Surface water, and Groundwater.
ii. Water quality (Electrical Conductivity (EC), Sodium, Calcium, and Magnesium)
6. Crop
i. Type of crop - Paddy and Other Field Crops (OFCs)

1
Exercise

Walk from the highest point to the lowest point along the undulating terrain inside the university
premises and observe the following features:

1. Location of irrigation channels.

2. Location of farm roads.
3. Location of farm buildings.
4. Location of wells.
5. Variation of the land slope.
6. Location of major soil groups
7. The soil texture and color
8. Surface drainage condition.
9. Location of natural waterways.
10. Location of perennial crops.
11. Location of paddy fields.
12. Location of other field crops (OFC) fields.

Assignment: Sketch the landscape and comment on your observations.

Figure 1.1: Typical dry zone terrain

2
 RF vs PET - Mahailluppallama
300 300

250 250

Rainfall (mm/month)

PET (mm/month)
200 200

150 150

100 100

50 50

0 0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Month
Rainfall (mm/month) PET (mm/month)

Figure 1.2: Rainfall and PET in Mahailluppallama

200

150
Available water (mm/month)

100

50

0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
-50

-100

-150

-200
Month
Figure 1.3: Change of Available water in Mahailluppallama

References:

https://www.fao.org/3/t0715e/t0715e06.htm

https://www.jircas.go.jp/sites/default/files/publication/tars/tars24-_12-29.pdf

https://esdac.jrc.ec.europa.eu/content/soil-map-sri-lanka

http://lk.chm-cbd.net/?page_id=176

https://edepot.wur.nl/482354
3
Notes:

4
PRACTICAL NO. 2
MEASUREMENT OF HORIZONTAL DISTANCE

Measurement of horizontal distance

Horizontal distance means the distance between two points measured at a zero percent slope.

If the two points are in different heights,

The horizontal distance between those two points, is the distance measured between the
vertical plumb lines dropped from each point to the same horizontal plane.

Methods

1. Pacing
2. Using a Measuring wheel / Odometer
3. Taping / Channing
4. Stadia
5. Electronic Distance Measurement (EDM) Technique

Pacing

Pacing is a non-equipment method of measuring the horizontal distance. It is a quick and

approximate measurement. Walking steps between two points are counted and multiplied by the
length of a step to determine the horizontal distance.

Two methods to calibrate pace distance (step)

● The average length of the individual’s normal pace

● Adjust one pace to a predetermined length

The accuracy of this method is 1/50, which means a 1 m difference in reading, can be observed
for 50 m of measurement.

Figure 2.1: Pacing

5
Measuring wheel (Odometer)

This is a movable wheel with a handle and recorder. When

the wheel is moving on the ground, the meter will indicate
the distance in length. This will give the length along the
surface between the points rather than the horizontal
distance.

Figure 2.2: Odometer

Stadia

The stadia method is a rapid means of determining horizontal distance by using Theodolite or
auto level. In some cases, the accuracy of this method is not sufficient. The general principle of
stadia measurement involves the reading of values on a leveling rod intersected by two horizontal
crosshairs that are always in the telescope of a transit. The horizontal distance between the rod
and the instrument is given by the equation.

𝐷 = 𝐾𝑆 + 𝐶

Where, D – Horizontal distance

K – Stadia multiplication Constant

S - Difference between the upper and lower stadia readings

C – Constant

Figure 2.3: View through

Telescope

Figure 2.4: Stadia

6
Taping

Taping is the most common surveying method used for measuring horizontal distance. In addition
to the requirement of the tape, plumb bobs, range poles, taping pins, and hand level are used in
taping. The Head tape man would walk with the “0” end of the tape to the other point while the
rear tape man would remain at the initial point.

Figure 2.5: Taping

Electronic Distance Measurement (EDM)

Figure 2.6: EDM

An electronic distance measuring equipment is a surveying instrument that uses electromagnetic

waves to measure the distance between two points. Electronic distance measuring (EDM) is a
technique for determining the length between two sites that makes use of phase shifts that occur
as electromagnetic energy waves flow from one end of a line to the other.

Exercise:

Select Point A and B on the ground approximately 200 m between them. Measure the distance
from A to B using all the above methods. Compare the measured values. Comment on the
accuracy, advantages, and disadvantages of each method.

7
References:

https://www.e-education.psu.edu/geog160/node/1926

https://www.fao.org/fishery/static/FAO_Training/FAO_Training/General/x6707e/x6707e02.htm

https://www.youtube.com/watch?v=tNRZPHLwC7k

Notes :

8
PRACTICAL NO. 3
MEASUREMENT OF VERTICAL DISTANCE (DIFFERENTIAL LEVELING)

Measurement of vertical distance (Differential Leveling)

Differential leveling is done to find the difference in elevation between two points.

Vertical distance:

It refers to the distance along the vertical line, which is the direction of gravity. This is a line that
is passing through the given points and the center of the earth.

Elevation:

It refers to the vertical distance above or below a reference level, usually mean sea level.

Benchmark (BM):

It is a relatively permanent point/object, in which elevation is already known.

Back sight (BS):

It is reading on a level rod held on a point of known elevation to determine the height of the
instrument.

Height of the Instrument (HI):

It is the elevation of the line of sight when the instrument is leveled. HI is determined by adding
the BS reading to the elevation of the point.

Foresight (FS):

It is a rod reading taken at a point of unknown elevation. The elevation of the point is determined
by subtracting the rod reading from the height of the instrument.

Turning point:

It is a temporary BM upon which FS and BS reading is taken to continue the line of level.

Intermediate Sight (IS):

Rod readings are taken between BS and FS readings.

9
Return check:

If there have been no errors made in the closed circuit of travel, notes for the returned check will
show the same elevation for starting BM. If there is a difference, that is the error of closure. The
permissible error of closure depends on the importance of the survey and the length of the circuit.

A reasonable allowance for agricultural purposes is given by the formula.

Allowable error = 0.10 √M Allowable error in ft, M = Total length of the loop in miles

Allowable error = 2.4 √km

Allowable error in cm, km = Total length of the loop in km

A benchmark is identified. A predetermined horizontal distance is taken and the points are marked
from the benchmark to the endpoint. Theodolite or the auto-level is leveled on the tripod. Then
the first back sight is taken by placing the measuring rod off the benchmark. Foresight reading is
taken on the next point. Then theodolite or the auto-level is moved to the next point. Then new
back sight-reading is taken. Then the measuring rod is moved to the next point to take the next
foresight. This is repeated until the endpoint.

4.765

Figure 3.1: Differential levelling

Recording differential leveling notes

Point Distance BS HI FS Elevation Remarks

(Reduced Level)

BM1

BM2
∑ BS ∑ FS
∑BS - ∑FS = BM1 – BM2
← Check →

10
References:

https://www.fao.org/3/r4082e/r4082e03.htm#2.4%20available%20water%20content

https://www.youtube.com/watch?v=G1sdsHZKUlQ

Notes:

11
PRACTICAL NO. 4
MEASUREMENT OF VERTICAL DISTANCE (PROFILE LEVELING)

Measurement of vertical distance (Profile leveling)

This is the process of determining the elevations of the points of measured distances along a
selected line. This line may be the centerline of the proposed channel, road, etc. Using the
information gained by this type of surveying we can plot the elevation of each point and distance
on a graph called a profile. With the aid of the profile, we can estimate cut and fill.

Keywords: - Bench Mark (BM), Back Sight (BS), Foresight (FS), Intermediate Foresight (IFS),
Height of the Instrument (HI), Distance and Elevation (Refer practical No 3). To verify the accuracy
of the leveling a “return check” must be made.

Intermediate Foresight (IFS):

It is a level rod reading alternating between BS and FS to find the unknown elevation. It can be
simply explained as FS that doesn’t establish a turning point.

Return check

If there have been no errors made in the closed circuit of travel, notes for the returned check will
show the same elevation for starting BM. If there is a difference, that is the error of closure. The
permissible error of closure depends on the importance of the survey and the length of the circuit.

Error of closure

A reasonable allowance for agricultural purposes is given by the formula.

𝐴𝑙𝑙𝑜𝑤𝑎𝑏𝑙𝑒 𝑒𝑟𝑟𝑜𝑟 = 0.10√𝑀 Allowable error in ft, M = Total length of the loop in miles

𝐴𝑙𝑙𝑜𝑤𝑎𝑏𝑙𝑒 𝑒𝑟𝑟𝑜𝑟 = 2.4√𝑘𝑚 Allowable error in cm, km = Total length of the loop in km

A benchmark is identified. A predetermined horizontal distance is taken and the points are marked
from the benchmark to the endpoint. Theodolite or the auto-level is leveled on the tripod. Then
the first back sight is taken by placing the measuring rod off the benchmark. A possible number
of intermediate foresight readings are taken from that point. Then theodolite or the auto-level is
moved to the next point. Then new back sight-reading is taken. Then the measuring rod is moved
to the next point to take the next intermediate foresight and the next foresight. This is repeated
until the endpoint.

12
 Then the elevation difference is plotted according to a scale. Then the optimum leveling profile
should be identified to minimize the earthwork or as preference.

Figure 4.1: Profile Levelling

Recording level notes.

Point Distance B.S H.I FS IFS Elevation Remarks

Reference:

https://www.charusat.ac.in/Downloads/Practical%20List%20and%20Lab%20Manual/CSPIT/CL/
CL%20242_Surveying_Manual18-19.pdf

http://www.nzdl.org/cgi-bin/library?e=d-00000-00---off-0cdl--00-0----0-10-0---0---0direct-10---4---
----0-1l--11-en-50---20-about---00-0-1-00-0--4----0-0-11-10-0utfZz-8-
00&cl=CL1.136&d=HASH013e8d1a442c5a625761db09.2.5.2&gt=1

https://www.youtube.com/watch?v=-S1FKc7U0rw

13
Notes:

14
PRACTICAL NO. 5
CHAIN SURVEYING

Chain surveying
This is a process of surveying an area using linear measurements only.
Reconnaissance:

You should walk all over the site to obtain a picture in your mind of the whole area while deciding
the most suitable way of carrying out the work economically in time and energy. While deciding
the best layout, you should prepare a sketch plan showing the lines chosen to form the framework
of the survey. During the reconnaissance, the following points must be considered; few survey
lines, long-baseline, well-conditioned triangles, check lines, obstacles, extension lines.

Baseline:

After reconnaissance, a baseline should be identified. The baseline is the longest straight line that
could cover the entire site. The baseline is positioned on the drawing sheet in such a way that the
whole area will be contained within the limits of the paper.

Triangles:

The base of chain surveying is triangles. The measured area is divided into the least possible
number of triangles. Well-conditioned triangles should have angles between 30 -120 degrees.

The triangles are drawn concerning the baseline.

Figure 5.1: Layout of a chain survey

15
Offset:

Perpendicular offsets are used in chain surveying. Distance is measured from the baseline to the
objects along with these offsets.

Perpendicular lines can be obtained by judging with the eye, the right angle formed between the
two tapes, by swinging the offset tape to obtain the shortest measurement, and with the optical
squire.

Figure 5.2: Offsets

Station marking:

What is a station? Stations must be easily and quickly found in the field and they should not be
readily disturbed. As stations are placed, they should be marked. This consists of making an
outline sketch of the immediate area around the station, showing existing permanent features,
the position of the station, and designation. Measurements are then taken from at least three
surrounding features to the station and recorded on the sketch.

Fieldnotes:

Should be clear and well-composed.

Figure 5.3: Field note of a chain survey

16
Detailed drawing:

As the offsets are plotted, they are joined up to correspond with the features noted in the field
book

Fair drawing:

Only the features of the field are traced. Title, Scale, North and other relevant notes are added.

Reference:

https://www.aboutcivil.org/how-to-methods-of-chain-survey.html

https://books.google.lk/books?id=NYUEeDJcVbEC&pg=PA35&lpg=PA35&dq=chain+survey&so
urce=bl&ots=ea2rEiV-
nM&sig=ACfU3U2uPHW1rSDeQ_iIUij3i6iTbSpjjQ&hl=en&sa=X&ved=2ahUKEwiYzvOemMr1Ah
U-ILcAHXMiAUE4ChDoAXoECAIQAw#v=onepage&q=chain%20survey&f=false

https://youtu.be/XsQi0Et5Ul0

Notes:

17
PRACTICAL NO. 6
TRAVERSING

Traversing

Traversing is defined as the measurement of lengths and directions of consecutive lines.

There are two types of the traverse.

(1) Open traverse (Employed in route surveys)

(2) Closed traverse (Employed for surveying a property)

Field method

First, select a place to traverse. The first point ‘A’ marks that corner point and set the
theodolite. Theodolite or the auto-level is leveled on the tripod. Ranging poles are
established at the ‘B’ and end point. The difference between these two readings gives the
angle of ‘A’ point. Lengths between points can be measured with a tape or using any method
discussed in practical No. 1, depending on the accuracy required. Then theodolite or the
auto-level is moved to the ‘B’ point. Then new readings are taken. This is repeated until the
end point. Directions can be measured by measuring deflection angles in route surveys and
by measuring interior angles in property surveys.

D
E

C B

Figure 5.4: Closed Traverse

18
Recording data in the field:

Point Length of line Interior/Def. angle

Angle closure:

Traversing starts at a certain point and ends at that point; it is considered a closed traverse. When
a close traverse is run, an excellent check on the angular measurements is available sum of the
interior angles.

AllowableTheoretical Sum division

closure = least readable
of Interior angles on the instrument
= (n-2) × 1800 × √n

Where the ‘n’ is the number of sides of the polygon.

Latitude and departures:

There can be considerable error in the measurements of lengths. Therefore, in order to check the
error of closure for the entire survey, Latitude and Departure of each line should be computed.

Latitude = length × Cos of bearing

If the bearing is ‘N’ latitude is positive and if bearing is ‘S’ then latitude is negative

Departure = length × Sin of bearing

If the bearing is ‘E’ departure is positive and if bearing is ‘W’ then departure is negative.

The error of closure (ec) = √{(∑L)2 + (∑D)2}

Where, ∑L is algebraic sum of latitude and ∑D is algebraic sum of departure

Precision of closure (Pc) = ec/P

Where P = perimeter of the traverse

Pc for rough work 1/ 1000; for accurate work 1/ 4000 and for extremely accurate work 1/
10,000 might be reasonable.

19
Determining Area and location:

After the error correction the lengths and interior angles can be used to find the area of the
enclosed polygon. And the locations of the points can be determined in an open traverse.

Reference:

https://www.youtube.com/watch?v=7slV7bl3Dds&list=PLH4lR7bcTmFmwqaikJkpoQjrPp4
tpA7j6&index=8&t=27s

https://theconstructor.org/surveying/traversing-surveying-types-methods/35684/

Notes:

20
PRACTICAL NO. 7
CONTOUR SURVEYING

Contour surveying

● The process of determining the elevation of distinct places on the ground and placing
them in the same horizontal position.
● Contouring can be classified into numerous groups depending on the equipment
utilized.
● Direct Method and Indirect Methods.
Indirect method

• Levels are only taken at a few specified spots.

• Specified points measured and plotted on a map.
• Reduced levels are noted and contour lines are interpolated between the specified
points.
• Approaches can be used to choose points -

1. Method of squares
2. Method of cross-section
3. Radial line method

Method of squares

Area is divided into squares, and points are located in the corners, marked by pegs. Place the
theodolite in an appropriate location where the elevation is known. Take the staff reading at
specified points and determine the elevation on each point. Interpolate the grid to construct the
contour lines.

Figure 7.1: Field note of Contour survey

21
Interpolation

● Following methods can be used to interpolate contour points between the two points:
▪ Estimation
▪ Arithmetic calculation,
▪ Mechanical or graphical techniques.
● The mechanical or graphical method of interpolation involves utilizing a tracing sheet to linearly
interpolate contour points: Several parallel lines are drawn at regular intervals on a tracing
sheet.
● To make counting easier, every tenth or fifth line is darkened.
● If A's RL is 97.4 and B's is 99.2 m, then assume that the bottom darkest line represents 97 m
RL and that each parallel line is spaced at 0.2 m intervals.
● Then, on A, keep the second parallel line in place.
● Rotate the tracing sheet so that point B is intersected by the parallel line 100.2.
● The spots on the 98 m and 99 m contours are shown by the junction of black lines on AB.
● Similarly, any line joining two adjacent points has contour points.

Figure 7.2: Interpolation

Drawing contours

Smooth contour lines are generated after identifying contour points and linking corresponding
points on a contour line. Distinguishing features of the ground should be expressed. Generally,
every fifth contour line has been thickened. Every contour line has its elevation indicated on it,
when the map is particularly large, it is also written at the ends.

22
References:

https://theconstructor.org/surveying/contouring-methods-maps-uses/6451/

https://www.youtube.com/watch?v=GuBdpeKfmho&list=PLH4lR7bcTmFmwqaikJkpoQjrPp4tp
A7j6&index=10

https://www.philadelphia.edu.jo/academics/aassouli/uploads/09-contouring%201.pdf

Notes:

23
PRACTICAL NO. 8
MEASUREMENT OF IRRIGATION WATER

Measurement of irrigation water:

Measurement of irrigation water is essential for efficient irrigation management. Water is

measured under two conditions; at rest (amount of water available) and in motion (amount of
water used). Water at rest is measured in volume units such as liter (L), cubic meter (m3), million
cubic meters (MCM), acre-feet (ac-ft), hectare-centimeter (ha-cm), etc. Water in motion is
expressed in rate of flow units such as liters per second (L/s), liters per hour (L/h), cubic meters
per second (m3/s), etc.

Flow measurement:

01. Area - Velocity Method

Float method, current metering

02. Weirs

Rectangular, trapezoidal, v-notch

03. Flumes

Parshall flume, cut-throat flume

04. Orifice

Circular, rectangular

01. Area - Velocity Method:

Continuity equation (Q = AV) is used in flow measurements, where Q is discharge rate, A is

cross-sectional area, and V is velocity of flow.

Float method

This method involves measuring the velocity of an object floating on the surface of the
flowing water and physically measuring the cross-sectional area of the flow.
A relatively straight, uniform section of about 25 m length is selected for this purpose. A
floating object such as a coke or a closed bottle is dropped at the middle of the canal, and
the time required for it to travel a known distance (e.g., 25 m) is measured.

Surface velocity = Distance travelled / Time taken

Average velocity = Surface velocity x 0.85

24
 The cross-sectional area of the flow is physically measured at least at three points (start,
middle and end) and averaged to obtain the average cross-sectional area.

Average discharge = Average cross-sectional area x Average velocity

This method is suitable for smaller canals only. For larger canals, current metering is
proposed.

Current metering

In this method, the flow section is divided into a few vertical profiles. The average
velocities of the individual profiles are measured at the middle of the profile using a
current meter, and the cross-sectional areas of the profiles are physically measured.

The velocity of a profile is

measured at two depths, namely
0.2 and 0.8 of the vertical depth,
and averaged to obtain the
average velocity of the profile.

If the depth is insufficient to

make two velocity
measurements, only one
measurement is made at 0.6 of
the vertical depth from the
bottom.

Figure 8.1: Current meter

Figure 8.2: Current method profile

25
02. Weirs

Weirs generate ‘critical flow conditions’ in a canal by contacting the flow vertically to use the ‘critical
energy principle’ for flow measurements. However, they require a substantial drop in downstream
heads to produce free flow over the crest. According to their geometry, they are named rectangular,
trapezoidal and V-notch (Fig.). The weir wall must be vertical and perpendicular to the flow. They
are easy to construct and install but may require a weir box to reduce the approach velocity to less
than 15 cm /s. Deposition of sediment and other debris might necessitate frequent cleaning.

Equations for different weirs

● RECTANGULAR WEIR:
Suppressed weir (weir crest extends to the full length of the canal):

Q = 0.0184 L H3/2

Contracted weir (weir crest does not extend to the full length of the canal):

Q = 0.0184 (L - 0.2H) H3/2

● Cipoletti weir (a trapezoidal weir with 1:4 side slope): Q = 0.0186 L H3/2

● V- NOTCH WEIR (90 O ): Q = 0.0138 H 5/ 2

where, Q - Discharge rate (l/s)

L - Length of crest (cm)
H - head above the crest level (cm)

Figure 8.3: Wiers

26
03. Flumes

Like weirs, flumes also produce

critical flow conditions by
contracting the flow horizontally.
Unlike weirs, they do not require a
drop on the downstream side to
produce critical flow conditions.
Therefore, they can be installed at
any location where a smooth flow
is present. Compared to weirs,
they are difficult to fabricate
accurately (Fig.). Due to the high
velocity at the throat, the problem
of sediment deposition will not
occur.

The Equations used to determine the flow rate vary depending on the throat width of the
flume.

For 3" throat width use

For 6" throat width use

For 9" throat width use

For 10" throat width use

For 2' through 8' throat width use

For 10' through 25' throat width use

Where:
= Flow Rate in cfs
= Height in feet
= Throat width in feet

Figure 8.5: Flumes

27
 04. Orifices

An orifice is a circular or rectangular opening through which water can flow. If the orifice
discharges entirely into the air, it is called free-flow condition, and if it discharges into the water
on the downstream side, it is called submerged condition.

It is easy to fabricate and install. Suitable for small flows. Sediment deposit and blockage due
to debris on the upstream side are common problems.

V = 0.61x10-3 . √2gH

Q = AV

Where, Q - Discharge rate through orifice (L/s)

A - Cross sectional area of the orifice (cm2)

g - Acceleration due to gravity (cm/s2)

H - Head (depth of water over the center of the orifice on the upstream side in case of
free flow orifice, or the difference in elevation between the water surface at the
upstream and downstream faces of the orifice plate in case of submerged orifice,
(cm)

Figure 8.6: Wiers

References:

https://www.openchannelflow.com/blog/methods-of-measuring-flows-in-open-channels

https://www.fao.org/3/t0848e/t0848e-09.htm

28
Notes:

29
PRACTICAL NO. 9
SPRINKLER EVALUATION

Sprinkler evaluation

In sprinkler irrigation, water is sprinkled to the atmosphere and allowed to fall on the soil and plant
surfaces like rainfall. This system's water application uniformity depends on operational pressure,
wind velocity, and spacing between sprinklers.

Objective

Evaluating the uniformity of application of a single sprinkler head operating under given conditions
(pressure, wind velocity, etc.).

Methodology

It involves setting up a pattern of catch cans around the sprinkler being evaluated and measuring
the catch in each can after operating the sprinkler for a specific period (Fig.).

• The water spread area around the sprinkler head is divided into squares of equal size and
the catch-cans (approx. l to 2 L cans) are placed at the middle of each grid square.
• The grids should cover the entire area of the water spread.
• Catch-cans should be placed about 2 m apart where the sprinklers are spaced about 10
m apart and about 3 m apart where the spacing is more than 10.
• Test should be carried out for a period equal to at least half of the planned duration of
application to accommodate the variation in wind speed, wind direction, solar radiation (air
temperature) and relative humidity.
• At the end of the test, the volume of water collected in each can is measured. The volumes
are converted to depths by dividing the volume by the cross-sectional area of the can.
• Uniformity coefficient (Cu) is computed using the formula proposed by Christiansen1942.

Figure 9.1: Layout of Catch can test

30
Christiansen’s formula to compute uniformity

Σ|Χ𝑖 − Χ̅| Σ|Χ𝑖 − Χ̅|

𝐶𝑢 = 100 ⟮1 − ⟯ 𝐶𝑢 = 100 ⟮1 − ⟯
𝑛Χ ΣΧ1

Where:

𝑋𝑖 -Individual observation

𝑛 -Number of observations

Χ̅ -Mean of observations (𝛴𝑋𝑖/𝑛)

|Χ𝑖 − Χ̅| -Absolute deviation from the mean

𝛴 |Χ𝑖 − Χ̅ |/ 𝑛 -Mean of deviation

Cu > 80% is considered satisfactory under normal wind conditions, however, Cu< 80% also
could be considered satisfactory in wind area. Local research is needed to arrive at a satisfactory
value for the prevailing conditions.

• ‘Cu’ can be re-computed for overlapping conditions by assuming different

spacing and arrangements (square, rectangular, triangular).
• Other parameters monitored are, discharge rate, pressure at the nozzle, wind
velocity and direction, air temperature, evaporation, relative humidity and crop
and soil damage due to drop impact.

Figure 9.2: Layout of spray area

31
Suggested sprinkler spacing to achieve good uniformity

Average wind velocity Spacing (% of the Overlapping (% of the

(km / hr) diameter of coverage) diameter of coverage)

No wind 65% 35%

0-6.5 60% 40%
6.5-13 50% 50%
>13 30% 70%

Results and discussion

Example:

Depth of water (mm) collected during a two-hour evaluation is given. Calculate the uniformity
coefficient (Cu)

3 5 8 8
5 10 15 13 Diameter of Coverage
5 10 16 15
5 13 15 13

16 m

Answer:

𝛴𝑋𝑖 = 159

N = 16

Χ̅ = 9.94 mm = 10 mm

7 5 2 2
5 0 5 3
5 0 6 5
5 3 5 3

𝛴 |Χ𝑖 − Χ̅ |= 61

Cu = 100 (1-61/159) = 62 %

32
 Exercise:

1. Conduct sprinkler evaluation

2. Do the necessary computations
3. Comment your results

Reference:

https://aces.nmsu.edu/pubs/_h/H510.pdf

https://www.canr.msu.edu/uploads/235/67987/ASAE_S436.1.pdf

https://agritech.tnau.ac.in/agricultural_engineering/spring_irrigation.pdf

Notes:

33
PRACTICAL NO. 10
1. ENGINES

Introduction

George Brayton, an American, invented the first commercial liquid-fueled internal combustion
engine in 1872. The compressed charge, four-stroke cycle engine was patented in 1876 by Nicolaus
Otto, Gottlieb Daimler, and Wilhelm Maybach. Karl Benz invented a dependable two-stroke gas engine
in 1879.

Potential energy is converted into kinetic energy by small engines. The basic concepts of heat,
force, pressure, torque, work, power, and chemistry are used in all internal combustion engines.

A two-stroke engine is an internal combustion engine that completes one power cycle with two
strokes (up and down motions) of the piston, with the power cycle being finished in one crankshaft
rotation. During two crankshaft rotations, a four-stroke engine requires four piston strokes to complete
a power cycle (Figure 1.1). The end of the combustion stroke and the start of the compression stroke
occur concurrently in a two-stroke engine, with the intake and exhaust functions occurring at the same
time.

Two stroke engine Four stroke engine

Figure 1.1: Cross section view of two stroke engine (Left) and four stroke engine (Right)

34
Two-stroke cycle

On the upstroke, the compression and ignition steps are combined, and on the downstroke, the
power and exhaust steps are combined. This method has fewer moving components, making
maintenance easier, but it produces less torque (Figure 1.2).

The two-step process includes:

1. Upstroke
(ignition/compression): The piston
goes up, air and fuel enter the
crankcase. The fuel-air mixture is
compressed and ignited.
2. Downstroke (power/exhaust): Once
the fuel is ignited, the piston is pushed
down, and the exhaust is expelled.

Figure 1.2: Two stroke cycle

Four stroke cycle

Four-stroke engines are fuel-efficient and environmentally-friendly. They operate in four steps: as
shown in Figure 1.3.

1. Intake: The intake valve is open, and fuel is drawn in with a downward stroke.
2. Compression: As the piston moves upward, the fuel is compressed.
3. Power: After the fuel is compressed, it is ignited to produce the engine’s power.
4. Exhaust: The exhaust valve opens, and the exhaust gases exit the cylinder.

Figure 1.3: Four stroke cycle

35
References:

https://primesourceco.com/latest-news/the-difference-between-a-2-stroke-and-4-stroke-engine/

https://en.wikipedia.org/wiki/Two-stroke_engine

https://www.researchgate.net/publication/260878177_Electric_and_Hybrid_Vehicles_-
_Technologies_Modeling_and_Control_A_Mechatronic_Approach/figures?lo=1

Notes:

36
2. TRACTORS

A tractor is an engineering vehicle designed to generate high torque at low speeds for dragging
a trailer or machinery used in agriculture, mining, or construction. Agricultural equipment/implements
can be trailed behind or mounted on the tractor, and if the equipment/implement is mechanized, the
tractor can also supply power.

A two-wheel drive (2WD) tractor sends engine power to two wheels to get the vehicle moving
(Figure 2.1). On the other hand, a four-wheel drive (4WD) model sends power to all four wheels, so it
can take on muddy and snowy conditions more confidently (Figure 2.2). Compared to 2WD and other
drivetrain options, a 4WD system can provide a safer and more controlled experience when you're
working under less-than-perfect conditions.

Figure 2.1: Two-wheel tractor

37
Figure 2.2: Four-wheel tractor

38
3 points link and Power take off (PTO) in tractors

The three points link (Figure 2.3) is a popular attachment for connecting ploughs and other
farming implements to a tractor. The three points resemble either a triangle, or the letter A.

Figure 2.3: Three points link and PTO

39
References:

https://www.centralarkansasmahindra.com/blog/2wd-vs-4wd-tractors--
34184#:~:text=A%202WD%20tractor%20sends%20engine,and%20snowy%20conditions%20more%20confiden
tly.

https://encyclopedia2.thefreedictionary.com/Agricultural+tractor

https://www.youtube.com/watch?v=P325ZdWSC7c

https://www.youtube.com/watch?v=pQGwNXFz8OY

Notes:

40
3. IDENTIFYING MACHINERIES FOR AGRICULTURE

Farm mechanization involves the use of mounted equipment to the tractor to accomplish tasks
previously done by man or animals. Plowing equipment attached to tractors and used for land
preparation. Proper soil preparation is required for the growth of seeds/plants.

Farm machineries used in

• Land clearing
• Tillage and seedbed preparation
• Fertilizer application
• Broadcasting or drilling of seeds
• Transplanting
• Pest and disease control
• Weed control
• Harvesting
• In-field transport of the harvested crop

3a. MACHINERIES FOR LAND PREPARATION

The purpose of land preparation is to provide the necessary soil conditions.

• Improves and restore soil fertility
• Ensures proper aeration and good root penetration
• Proper land levelling
• Improves soil workability
• Improve structure of the soil

Primary Tillage

Tillage applied to break the compacted soil into soil clods. More aggressive, deeper operation and
usually leaves the surface rough. Some of implements used in primary tillage are shown in Figure 3.1.

The purposes of primary tillage are;

• Loosen the soil structure

• Bury the plant waste
• Erosion control
• Preparation for secondary tillage
• Weed control
• Kill pest

41
Disc Plough Moldboard Plough

Rotary Tiller Chisel Plough

Subsoiler

Figure 3.1: Primary Tillage Implements

42
Secondary Tillage

Tillage applied to reduce the size of soil aggregates and to level the soil surface after done with
primary tillage. Works the soil to shallow depth. The implements use in secondary tillage are shown
Figure 3.2.

The purposes of primary tillage are;

• Break the soil clods

• Shatters the soil clods
• Level the soil surface
• Harrow the soil and plant waste (stubbles)
• Firm the soil
• Kill weeds and helps conserve moisture

Disc Harrow
Spike tooth Harrow

Spring tooth Harrow Rigid tined cultivator

Figure 3.2: Secondary Tillage Implements

43
3b. SEEDER AND TRANSPLANTER

Seeders and transplanters/planters are essential for crop establishment. Their function is to
measure and plant seeds or plants, or parts of them, in the soil. Seeders are used for generative crop
establishment, whereas planters are utilized for vegetative crop establishment. However, in certain
places of the world, a seeder is referred to as a planter.

The objective of sowing is to plant seeds at a correct depth in the soil with the best possible
spacing between them. Comparative experiments have frequently demonstrated that accurate seed
placement delivers greater and more consistent average yields than the random seed placement. The
objective of a seeder is to achieve such accurate and reliable seed planting in a timely and cost-effective
manner. Figure 3.3 illustrates a manual seeder. Figure 3.4 shows a rice transplanter. There are seeding
machines available for crop establishment in large fields.

Figure 3.3: Manual seeder

44
Figure 3.4: Rice transplanter

45
3c. WEEDER

Weeds can be cut, uprooted, thoroughly mixed with the soil and bury weed residues in the soil
by rotary cutter blades. This weeder can adjust the weeding length of rotary blades from 150mm to
300mm according to varied row spacing and can use as a multi-purpose machine for dry land weeder
and tiller.

Various types of weeders

• Ring Hoe
• Cono weeders (Figure 3.5)
• Straight-spike floating weeder
• Curved-spike floating weeder
• 2-row curved spike floating weeder
• Twisted-spike floating weeder
• Straight spike weeder
• 2-row spike and blade weeder

Figure 3.5: Cono weeder

46
3d. SPRAYER

Sprayer is a device used in agriculture used to spray liquids like water, insecticides, and
pesticides in agriculture. They are also used to spray herbicides and fertilizers to crops in agriculture.
There are number of sprayers which are designed for different spraying applications like garden,
agricultural crops including fruit and vegetable and livestock needs.

Various types of sprayers

• Knapsack Sprayer (Figure 3.6 - Left)

• Portable Power Sprayer
• Knapsack Power Sprayer
• Boom Sprayer (Figure 3.6 - Right)
• Mist Dust Sprayer
• HTP Sprayers
• Orchard Sprayers

knapsack sprayer Boom sprayer

Figure 3.6: Knapsack sprayer (Left) and Boom sprayer (Right)

References:

https://www.youtube.com/watch?v=bOvnUo6-6Ds

https://www.youtube.com/watch?v=9fMNO-1Q5es

http://www.nzdl.org/cgi-bin/library?e=d-00000-00---off-0hdl--00-0----0-10-0---0---0direct-10---4-------0-1l--11-en-
50---20-about---00-0-1-00-0--4----0-0-11-10-0utfZz-8-
00&cl=CL1.8&d=HASHe51c1b601305eaad3be351.11.5&gt=1

http://www.ricehub.org/RT/weeds/weeders/

https://www.kisankraft.com/different-types-of-sprayer-and-its-uses/

47
Notes:

48