CS 204 PRINCIPLES OF AGRONOMY 2022 [Compatibility Mode].pdf

Principle and practice of field management

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SOKOINE UNIVERSITY OF AGRICULTURE
COLLEGE OF AGRICULTURE
DEPARTMENT OF CROP SCIENCE AND
HORTICULTURE
CS 204 : PRINCIPLES OF AGRONOMY
Ms.HEKIMA B MLIGA
5/20/2022
CS 204
•PRINCIPLES OF AGRONOMY 5/20/20222
3
Learning outcomes
Upon completion of the course students are expected
to:
•Manage crops and soils for improved productivity
•Decide on the best production options given a set o f
environmental conditions
•Decide on the best farming systems for different
locations
•Make various land measurements and determine
slopes of farm plots.
•Plan and implement field crop experiments
4
Subject contents
•
Definition of agriculture
,
meaning and scope of agronomy
; History and development
of agriculture in Tanzania, Importance of agriculture in Ta nzania,
Agro climatic zones
of Tanzania
.
Tillage and tilth: objectives of tillage, characteristic o f ideal seed bed,
effect of tillage on soil properties: pore space, texture, s tructure, bulk density and
colour of the soil. Types of tillage: preparatory tillage, f actors affecting preparatory
cultivation, after cultivation and puddling
. Sowing techniques, Crop establishment;
factors affecting optimum stand establishment. Planting g eometry, competition,
effect of plant population on growth and yield.
Optimum plant density and planting
pattern
. Soil fertility considerations: fertilizers and fertiliz er formulations, application
methods. Weeds and their effects on crop production. Concepts in weed
management.
Concepts in crop irrigation for optimized yield
.
Cropping systems:
definition and principles of crop rotation, mixed cropping , relay cropping, multistoried
cropping, sole cropping and techniques and cropping sequence
. Harvesting and
postharvest technology for major agricultural crops – rice , maize, groundnut and
pulses. Principles and practices in arid and semi-arid crop production.

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Practical skills
•Simple land measurement techniques and tillage
•Fertilizer formulation, calibration, storage and fi led
application
•Seed selection, calibration and sowing techniques
•Laying out field experiment
•Simple soil sampling techniques
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INTRODUCTION
•Agriculture is derived from Latin wordsAgerand
Cultura.
•Ager means
land
or
field
and Cultura means
cultivation.
•Therefore the term agriculture means cultivation of
land.
•It is also referred as the science of producing crops
and livestock from the natural resources of the
earth.
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Introd……..
•Agricultureis defined as the
art
and
science
of growing
plants and other crops and the raising of animals for food,
other human needs, or economic gain .
•
Production, Improvement, Protection, Processing,
Marketing, Extension of crop using natural resources
•As an art-
it embraces knowledge of the way to
perform the operations of the farm in a skilful
manner.
•The skill is categorized as;
a) Physical skill: It involves the ability and capacity to
carry out the operation in an efficient way for e.g .,
handling of farm implements, animals etc., sowing
of seeds, fertilizer and pesticides application etc .
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b)Mental skill:The farmer is able to take a decision
based on experience, such as;
(i) Time and method of ploughing
(ii) Selection of crop and cropping system to suit soil
and climate
(iii) Adopting improved farm practices etc.
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•As a science •It utilizes all modern technologies developed on
scientific principles such as crop
improvement/breeding, crop production, crop
protection, economics etc., to maximize the yield
and profit. Example; new varieties, pesticides etc
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What is a crop?
An organism grown or harvested for obtaining yield,
which has economic value. e.g., rice, fish, cattle,
poultry
•Basically
,
Agriculture deals with both animals and
plant that have economic values.
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Branches of Agriculture

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•Broadly in practice, agriculture is grouped in
four
major categories as,
•A. Crop Improvement •(i) Plant breeding and genetics
•(ii) Bio-technology
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B. Crop Management •(i) Agronomy
•(ii) Soil Science and Agricultural Chemistry
•(iii) Seed technology
•(iv) Agricultural Microbiology
•(v) Crop-Physiology
•(vi) Agricultural Engineering
•(vii) Environmental Sciences
•(viii) Agricultural Meteorology
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•C. Crop Protection •(i) Agricultural Entomology
•(ii) Plant Pathology
•(iii) Nematology
•D. Social Sciences •(i) Agricultural Extension
•(ii) Agricultural Economics
•Allied science: Agricultural statistics ,English,
mathematics, biochemistry
5/20/202216 DO YOU REMEMBER THE PROCESS OF
EVOLUTION IN AGRICULTURE??????
•EXPLAIN ………

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Evolution of Agriculture
Principles of Agronomy
•The word agronomy has been derived from the two
Greek words, agrosand nomoshaving the meaning of
field
and to
manage
, respectively.
•Literally, agronomy means the “art of managing
field”.
•Technically, it means the “science and economics of
crop production by management of farm land”.
•Agronomy is the art and underlying science in
production and improvement of field crops with the
efficient use of soil fertility, water, labourer and other
factors related to crop production.
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Principles of Agronomy
•Agronomy: the art, science and economics of crop
production by management of farmland.
•Basic principles of agronomy includes:

Planining, programming and executing
Choice of crop varieties
Proper field management
Multiple cropping systems
Timely application of proper balanced nutrients
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Principles of Agronomy
choice of quality seed material
Proper water management
Plant protection measures and
suitable method of harvesting & postharvest
management technologies.
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•Among all the branches of agriculture, agronomy
occupies a pivotal position and is regarded as the
mother branch or primary branch.
•Like agriculture, agronomy is an integrated and
applied aspect of different disciplines of pure
sciences.
•Agronomy has three clear branches namely, (i) Crop
Science, (ii) Soil Science, and (iii) Environmental
Science that deals only with applied aspects.
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•Who is the agronomist? “ A scientist who studies the principles and practices of
crop production and soil management for production
of food for human beings and feed for animals.
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Roles of agronomist
•Generally agronomist studies the problems of crop
production and develops better ways of producing
food, feed and fibre.
•Agronomist aims at obtaining maximum production
at minimum cost
•Agronomist shoulder the responsibilities of all soc ial,
economic, cultural problems in addition to field
problems for the effective functioning of the farm in
general.
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•Agronomist exploits the knowledge developed by
basic and allied, applied sciences for higher crop
production.
•Agronomist carries out research on scientific
cultivation of crops.
•He has to identify various types of nutrients requi red
by crops.
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Classification of agronomic crops
•Cereals: rice, wheat, maize, barley.
•Oil seed crops: Mustard, soybean, sesame, linseed,
safflower, sunflower, groundnut
•Pulse crops: black gram, lentil, grass pea, cow-pea,
soybean, peas
•Forage crops: cowpea, maize, para grass, oats,
napier grass
•Fibre crops: cotton, stem or bark of such as jute
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•Sugar crops: sugarcane, sugarbeet
•Green manuring crops: cowpea, green gram
•Narcotic /drugs crops: tobacco, cannabis
•Beverage crops: tea, coffee, cocoa
•Special purpose agronomic crops 
Catch Crops
Cash Crops
Cover Crops
Mulch Crops
Restorative Crops
Importance of agriculture in Tanzania
Importance
Challenges
Opportunities
Read and be able to explain the three concepts 5/20/202228

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Importance of agriculture in Tanzania
•Source of income
•Food and fibres
•Feeds
•Raw materials
•Foreign exchange
•Employment
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Agro-climatic zones
•Tanzaniahas a tropical climate.
•There are 4 main climatic zones
(i) Hot humid coastal plain
(ii) The semi-arid central plateau
(iii) The high rainfall lake regions
(iv) The temperate highlands.
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Agro-ecological zones(agriculture
zones)
1. Central zone-Makutupora
2. Eastern zone-Ilonga
3. Southern zone-Naliendele
4. Northen zone-Selian
5. Lake zone-Ukiriguru
6. Southern highlands-Uyole
7. Western zone-Kihinga
8. Zanzibar-ZARI
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•Tanzania has two major rainfall regimes. One is uni-
modal (October–April) and the other is bi-modal
(October–December and March–May).
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Tanzania has two major rainfall regimes. One is
uni-modal (October–April) and the other is bi-
modal (October–December and March–May).
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ASSIGNMENT NUMBER 1
•Write short notes on the four climatic zones in
Tanzania giving out relevant examples of regions an d
crops commonly produced in the zones.
•Include reference and citation
•Use SUA format; Times New Roman,12,1.5maximum
4 pages including cover page and reference page
•ASSIGNMENT TYPE:INDIVIDUAL BASED
•Submission date: during next class session
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Topic two: Tillage
•Definition:
Tillageinvolves the mechanical manipulation of the
soil, in a number of ways to produce an
environment, which is satisfactory for the crop
development, drainage and mechanization
operations.
Such mechanical agitation of the soil involves
digging, stirring, and overturning. Examples of
human-powered tilling methods using hand tools
include shovelling, picking, mattock work, hoeing,
and raking and using power driven impliments such
as
Mouldboard
plough,
chisel,
harrow
etc
.
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General Purposes of tillage
a) Control of residues(effective use of residues)
b) To develop a desirable soil structure for a seedb ed
c) Control of competing vegetation
d) Control of flow of water(drainage)
e) Control the distribution of fertilizer.
f) To establish specific surface configuration for
planting, irrigation, drainage and harvesting
operations.
g) To incorporate and mix fertilizers, pesticides or soil
amendments into the soil.
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Primary purpose of tillage
•Reduce soil aggregates or clod size
•Form aggregates small enough around the seed and
seedling to prevent drying of the soil
•Provide adequate aeration
•Provide sufficient soil solution.
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•Two major classes:
1. Primary tillage:
Constitutes the initial major soil working operation
designed to reduce the soil strength , cover plant
materials and rearrange aggregates.
2. Secondary tillage
Breaks down
large clods into finer granules
and
aggregates producing the ‘just right’ combination of
air and water retention and easy penetration of
plant roots and emergence of seedlings
.
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Reading assignment
•Read and prepare your own notes on types of
secondary tillage implements and its functions
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Why secondary tillage?
It normally works the soil to shallower depths
It has an effect of pulverizing, leveling the soil and
killing weeds.
Refining the seedbed & controlling the weeds,
Incorporation of chemicals into the soil and
management of residues.
Secondary tillage
operations depends on the
implement used.
•
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Tillage systems/Methods
1. Conventional tillage
2. Minimum tillage
3. Zero/No tillage
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1. Conventional tillage
•Refers to seedbed preparation which involves:
a. Complete ploughing of land by disking once or twice
b.Harrowing to pulverize soil and clear rubbish and
plant stubble
c. Prepares fine seedbed free of clods and soil
aggregates
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Advantages of conventional tillage
•Deals most effective with stubble
•Provides the most uniform seedbeds
•Has the best assurance of crop stand.
•Best weed control.
•Results in better insect / diseases control
•Greater soil nutrient mineralization
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Disadvantages of conventional tillage
•Leaves the surface susceptible to splash and sheet
erosion
•Smooth surface is susceptible to crusting
•Results in higher nutrient leaching
•Results in decline in organic matter content and
increased erodibility
•Results in a limited rooting volume due to higher
resistance layer formed at shallow depths
•Its energy intensive
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When to apply conventional tillage
•On relatively flat land
•On field where weed control is the priority
•To incorporate manure and crop residues
•Where fertility management is possible through
application of organic and inorganic fertilizers
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2.Minimum tillage
•Group of soil preparation methods over the field is
less than in conventional tillage.
•It is also referred asconservational tillagesince it
leaves 30% of crop residues on the soil.
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Advantages of minimum tillage
•It reduces farm expenses
•Reduces runoff
•Reduces sheet erosion
•Increases soil moisture retention
•Increases soil organic matter
•Reduces energy requirements
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Disadvantages of minimum tillage
•Conservation tillage requires expensive equipment
or a lot of manual labor.
•Unlike traditional methods of weed and pest control,
it demands more pesticides and herbicides;
•The first positive results of conservation tillage are
visible only in long-run.
•The method contributes to greenhouse gases
emission (CH4 and N2O)-LARGE SCALE FARMS
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3.No/Zero Tillage
•No-tillage farmingis a farming practice where the
soil is minimally disturbed from planting to harvest.
•The seeds are introduced without ploughing the soil.
•During the planting process: holes are drilled into
the soil where the seed will be planted.
•Then covered up
•This method: leaves ground surface in tact
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Advantages of No tillage
•Soil erosion is reduced •Farmers save money and increase their profits
•Reduced fuel and equipment operation
•Water Conservation
•Increases in Crop Yields
•Increases in beneficial insects and soil microbes
•High Resource Availability
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Disadvantages of No-Tillage Farming
•Special Machinery is Required
•Not Appropriate for Every Soil Type
•Increase in Herbicide Use
•No Baling or Heavy Grazing
•Nitrogen-based fertilizers may still be needed
•Increase Risk of Fungal Diseases
•Increased Herbicide Application
•Involves more management
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PHYSIOLOGY OF CULTIVATED PLANTS
•Plant physiologydeals with how a plant works or what
makes the plant click.On the other hand,crop
physiologydeals with functioning of crop plants
individually as well as a community of plants
Why plant physiology?
•Know how plants work under normal as well as
abnormal (stress) conditions
•Know how different crops and cropping systems respond
to external environment.
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•To improve and stabilize yield by choosing the right
kind of cultural practices.
What a plant is and what it may become depends
upon the following:
i. Genetic make-up -genotype, e.g. days to flower,
height, seed color
ii. Environment- soil, minerals, water, light,
temperature, etc.
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So physiology helps
•Designing (breeding)right kind of crop plant for a
given location season by exploiting the
environmental resources to the maximum extent.
•Formulating cultural practices to get maximum yield
with least inputs
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Basic Plant processes
•1. Photosynthesis:the process of converting solar
energy into chemical potential energy in the form of
carbohydrates synthesized by using CO2 from air and
water as raw materials.
•Photosynthetic efficiency (biomass/per light
absorbed):Photosynthesis is known to be a true
measure of crop’s yield-ability
•Carbon compoundsaccount for 80-90% of the total
dry matter produced by plants
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•Leaf area and photosynthesis
-the rate of extension of the leaf surface determine DM
- Leaf orientation and/or inclination with respect of
incoming solar radiation also determine DM
Differences in leaf area(LA) andleaf orientationare key
factors in the process of photosynthesis as they
influence solarradiation interception.
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•If LA and leaf orientation are combined with respect
to land area under the crop canopy, an important
attribute called leaf area index (LAI) comes into being.
LAI = LA/P
Where,P = ground area under canopy cover
LAIis the total leaf area per unit area of land surface
LAI has beenproposed as the best measure of the
capacity of a crop to produce DM.
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2.0 Respiration
•The processof releasing energy by oxidizing
(burning) carbohydrates.
•CO
2
, water and energy
•The energy released in respirationis utilized for
various biosynthetic reactions resulting in normal
functioning of the cell including growth
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3. Transpiration
•Transpirationis the process of internal water loss through
stomata, cuticle and lenticels.
•It has been shown that about 600kg of wateris
transpired by plants for each 1kg or dry matter (grain
produced in maize; and this being about 75% of water
added to the field.
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4.Translocation
•Ascent and descentof sap is important in the uptake
of H
2
O and nutrients for energy assimilation
(photosynthesis); and for transfer of assimilate to
storage and other organs.
•Ascenttakes place in xylem,descentin phloem
•Assimilates are translocated from source-sink
•Sinksmay includeflowers, fruits, growing points
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Plant Ideotypes
•Strictly,a plant ideotype is an ideal plant for
maximum productivity or yield.
•It is a plant formso synthesized (through
hybridization) that it posses the optimum
combinationoraccumulation of yield controlling
factors.
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Characteristics of an ideal cereal plant
•Should have small, erect, thick leaves and of compact
tillering habit for efficient light utilization.
•Should have short stems resistant to lodging and should
have high tillering ability and high panicle number (e.g.
in rice).
•Should be widely adapted.
•Should be insensitive to day-length for control of
flowering and shortening of the life cycle (not universally
applicable.
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Principles of Field Crop Establishment
•Tillage: One way of manipulating the soil condition to suit
crop establishment is tillage
The objectives of tillage are listed below
•Prepare suitable soil tilth (fine) for seed germina tion and
root establishment (mechanical penetration, aeratio n
•Incorporate organic matter (OM) in the soil
•Improve infiltration and soil moisture level and re duce run-
off losses
•Crush insect pests, expose them of their eggs to th e sun or
rain for destruction.
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•TEST ONE DATE
•PRACTICALS-Crop identification, tillage implements
,fertilizer applications and rate, land equivalent ratio.
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•LECTURE 3
Seed production
•A seedis a unit of propagation for most crops
•It is important to sow seed of proven good quality
•Assurance of good quality seedfor the major crops
is usually a public responsibility.
•It is carried out byOfficial Seed Certification-
Tanzania Official Seed Certification Institute
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The steps involved in the production of a new seed in
Tanzania include
•A breeder develops a new variety
•The breeder requests permission from the Seed Relea se
Committee to release the variety;
•If successful, the seed is certified as breeder Seedby
TOSCI
•If TOSCI is satisfied, the seed qualifies as Foundation
Seed; and
•The Foundation Seed is tested again and if found to be
all right, it is multiplied and sent to Seed Mercha nts as
Certified seed.
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Seed Quality Attributes
•Genetic purity (species, cultivars) – the seed should be
true to type.
•Analytical purity – should be free from crop debris,
soil stones, insects, and damaged seed.
•Freedom from weed seeds, e.g. striga
•Viable- the seed should be able to grow when planted
•Vigour- health seed give better seedlings and good
final crop establishment and yield
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•Germination– given the required conditions for
germination, i.e. optimum temperate, water and oxygen,
should be germinated. A good seed should have high
germination percent (90-100%).
•Disease free– seed borne diseases cause crop failure.
Any seed intended for sowing should be free from
diseases.
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Seed Sowing and Germination
•Sowing methods:
•Drilling (mechanized sowing)
•Broadcasting
•Dibbling (random spacing)
•Sowing depth: is determined by seed size
•Small seeds have little food reserves, thus the sowing
depth must ensure that emergence period is short
•Small seeds should not be sown deeper than 2-3 cm.
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•Large seeded cropse.g. maize and field beans can
be sown at 5 cm or more.
•When soil moisture is limiting , large seeds may be
sown deeper but this delay emergence.
•When you are not aware of the sowing depthfor a
particular seed, the best estimate would be twice
the seed’s diameter.
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Factors affecting seed germination after sowing
1. Seed dormancy
A state in whichseedsare prevented from germinating
even under environmental conditions normally favorable
for germination
2. Water
Seeds would need to imbibe up to 150% of their own
weight of H
2
O to begin the germination process
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Factors affecting seed germination after sowing
3. Oxygen
Sowing into very wet seedbeds limits O
2
availability
leading to poor germination of the seed.
4. Soil Temperature:There is an optimum range of
temperature for each crop,short of which will leadto
sub-optimal or slower germination.
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Table 3:
O
p
t
im
u
m

t
e
m
p
e
ra
t
u
re
s
se
e
d

g
e
rm
in
a
t
io
n

in

v
a
ri
o
u
s
cro
p

sp
e
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e
s

__________________________________________
________________
Crop Min
o
C Optimum
o
C Max oC
Maize 8-10 32-35 40-44
Rice 10-12 30-37 40-42
Wheat 3-5 15-31 30-43
Barley 3-5 19-27 30-40
Assignment
•Read about sowing methods
highlighting theiradvantagesand
disadvantages
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Seed rates
•Seed rate may be defined as the amount of seed
required for a unit area of land to grow any crop
successfully.
•It expressed in kg/ha.
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Importance/objectives of seed rates
•To ensure the number plant population in the field.
•To reduce the wastage of seeds.
•To know in advance the amount of seed to be
required for a particular land.
•To increase the yield and quality of a crop.
•To reduce the cost of cultivation of crops.
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Factors determining seed rate
•Desired plant population: This is flexible depending on
soil fertility, crop growth type and purpose of cro p.
Plant population = (Land Area (m
2
))/ (Area per plant (m
2
)).
•Germination percentage: if the percentage is low, higher
rates are recommended.
•Sowing method: drilling and broadcasting need higher
rates than space planting
•Purpose of crop: For example, if maize is sown for fodder,
higher rates are used.
•Late sowing: higher rates are required because there is
more opportunity for gap-filling.
91
Field factors:
Incidence of birds and rodent damage – use higher
rates
Poorly prepared seedbed requires high rates
Compacted seedbed – some seeds may not emerge
Moisture availability (e.g. deep sowing in dry
conditions, use higher rates)
Pathological factors
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Factors summary
Desired plant population (DPP)
Percentage of germination (PG)
Purity percentage (PP)
Pure Percentage of safety allowance (PSA)
Weight of seed.
The number of seeds per pit.
Planting method.
Soil productivity.
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Factors summary cont…
Varied morphology.
Growing season.
Viability of seed.
Age of seed.
Size of seed.
Objectives of crop cultivation – Food purpose, Seed
purpose.
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Calculating seed rates
•Rate (Kg/ha) = (Plants/m
2
x10000 m
2
)/seed/kg x
%germination) or,
•(Plants/m
2
x 10000 x 100) / (seed/kg x germination
(%)).
•Seed rate kg/ha=Area (m
2
)
×seed weight
×10000
spacing (m
2
)
×germination (%)
×Purity (%)
×1000
×1000
•
•Seed rate g/ha=Area (m2)×seed weight×10000/
spacing (m2)×germination (%) ×Purity (%)×1000
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2 2
Plants / m x10,000m
Rate(kg / Ha)
seed / kg germination%
=
´
C
o
n
si
d
e
ri
n
g

f
ie
ld

f
a
ct
o
r
s,

2 2
Plants / m 10,000m
Rate(Kg / ha) F
Seed / kg ger min ation%
´
= ´
´

F= (field factor)

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EXERCISES
1. Calculate the seed rate of mung bean for sowing 1
hectare of crop from the following
spacing=30cm×10cm germination %=92% purity
%=85% 1000 grain weight =36g
2. Calculate the seed rate of pigeon pea for sowing 1
hectare of crop from the following:
spacing=60cm×25cm germination %=87% field
factor %=14 % 1000 grain weight =70g
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Cop Establishment and Planting Density
•The effect of varying plant population , i.e. planting
density, on yield of crops is of utmost importance to
the grower
•The importance arises from the concept of crop
competition.
•Two types: Intra-specific competition and Inter-
specific Competition
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Intra-specific competition
•Plants compete for various growth resources of the
aerial and soil environments:
•Competition for light
•Competition for water and nutrients
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Inter-specific Competition
•Occurs whentwo or more cropsare grown on the
same piece of land at the same time or season.
•One crop may shade the other, causing
competition for light between them
•Competitionforwater and soil nutrientsoccurs as
the two or more crops stretch their root systems.
•Growth factors are to be suppliedto meet the
combined demand of the crops in the environment
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