Agl509

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Rain-fed Agriculture
(AGL509)
Mr. Rohitashv Nagar
Assistant Professor
Department of Agronomy
School of Agricultural Sciences
Career Point University, Kota (Raj.)

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Lecture-1
Dry land farming & Drought

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Dry land farming-introduction and definition and importance
Introduction:
Agriculture is the single largest livelihood sources in India with nearly two
thirds of people depend on it. Rainfed agriculture is as old as agriculture it
self. Growing of crops entirely under rainfed conditions is known as
dryland agriculture. Depending on the amount of rainfall received, dryland
agriculture can be grouped into three categories:

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a) Dry farming: is cultivation of crops in regions with annual rainfall less
than 750 mm. Crop failure is most common due to prolonged dry spells
during the crop period. These are arid regions with a growing season
(period of adequate soil moisture) less than 75 days. Moisture
conservation practices are necessary for crop production.
b) Dry land farming: is cultivation of crops in regions with annual
rainfall more than 750 mm. In spite of prolonged dry spells crop failure is
relatively less frequent. These are semi arid tracts with a growing period
between 75 and 120 days. Moisture conservation practices are necessary
for crop production. However, adequate drainage is required especially for
vertisols or black soils.

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C) Rainfed farming: is crop production in regions with annual rainfall
more than1150 mm. Crops are not subjected to soil moisture stress during
the crop period. Emphasis is often on disposal of excess water. These are
humid regions with growing period more than 120 days.

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Dryland vs. rainfed farming
Constituent Dryland farming Rainfed farming
Rainfall (mm) <800 >800
Moisture availability to
the crop
Shortage Enough
Growing season (days) <200 >200
Growing regions Arid and semiarid as well as
uplands of sub-humid and humid
regions
Humid and subhumid
regions
Cropping system Single crop or intercropping Intercropping or
double cropping
Constraints Wind and water erosion Water erosion

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Importance of Dry farming in Indian Agriculture
1. About 70% of rural population lives in dry farming areas and their
livelihood depend on success or failure of the crops
2. Dryland Agriculture plays a distinct role in Indian Agriculture occupying
60% of cultivated area and supports 40% of human population and 60 %
livestock population.
3. The contribution (production) of rainfed agriculture in India is about 42
per cent of the total food grain, 75 per cent of oilseeds, 90 per cent of
pulses and about 70 per cent of cotton.

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Problems or constraints for crop production in dry farming regions
The low productivity of agriculture in dry farming regions is due to the
cumulative effect of many constraints for crop production. The
constraints can be broadly grouped in to:
A) Climatic constraints
B) Soil related constraints
C) Socio economic constraints

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A) Climatic constraints:
1. Rainfall characteristics: Among the different climatic parameters rainfall
is an important factor influencing the crop production in dry regions.
(i) Variable rainfall: Rain fall varies both in time and space dimension. The
average annual rainfall of India is 1192 mm where as in Andhra Pradesh it
is 890 mm. More than one third of total geographical area in India receive
rainfall less than 750 mm.
(ii) Intensity and distribution: In general, more than 50 per cent of total
rainfall is usually received in 3 to 5 rainy days. Such intensive rainfall
results in substantial loss of water due to surface runoff. This process also
accelerates soil erosion. Distribution of rainfall during the crop growing
season is more important than total rainfall in dryland agriculture.

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iii) Aberrations or variations in monsoon behaviour
(a) Late onset of monsoon: If the onset of monsoon is delayed,
crops/varieties recommended to the region cannot be sown in time.
Delayed sowing lead to uneconomical crop yields.
(b)Early withdrawal of monsoon: This situation is equally or more
dangerous than late onset of monsoon. Rainy season crops will be
subjected to terminal stress leading to poor yields. Similarly, post-rainy
season crops fail due to inadequate available soil moisture, especially
during reproductive and maturity phases.

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(c) Prolonged dry spells: Breaks of monsoon for 7-10 days may not be a
serious concern. Breaks of more than 15 days duration especially at
critical stages for soil moisture stress leads to reduction in yield.
B) High atmospheric temperature: Because of high atmospheric
temperature the atmospheric demand for moisture increases causing high
evapotranspiration losses resulting in moisture stress.
C) Low relative humidity: Low relative humidity results in high ET
losses causing moisture stress whenever moisture is limiting.

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B. Soil Constraints:
a) Inadequate soil moisture availability: The moisture holding capacity of soils in
dry regions is low due to shallow depth especially in alfisols (red soils), low rainfall
and low organic matter content.
b) Poor organic matter content: The organic matter content in most of the soils
under dryland conditions is very low (< 1 %) due to high temperature and low
addition of organic manures. Poor organic matter content adversely affects soil
physical properties related to moisture storage.
c) Poor soil fertility: Due to low accumulation of organic matter and loss of fertile
top soil by soil erosion the dry land soils are poor in fertility status. Most of the
dry land soils are deficient in nitrogen and zinc.

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C. Socio-economic constraints: The economic condition of the dryland
farmers is very poor because.
a) Less access to inputs
b) Non availability of credit in time
c) The risk bearing capacity of dryland farmer is very low
Hence the dryland farmers resort to low input agriculture which results in
poor yields.

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Drought:
The irrigation commission of India defines drought as a situation occurring in
any area where the annual rainfall is less than 75% of normal rainfall.
Effect of drought on crop production:
a) Water relations: Alters the water status by its influence on absorption,
translocation and transpiration. The lag in absorption behind transpiration
results in loss of turgor as a result of increase in the atmospheric dryness.
b) Photosynthesis: Photosynthesis is reduced by moisture stress due to
reduction in photosynthetic rate, chlorophyll content, leaf area and increase
in assimilates saturation in leaves (due to lack of translocation).

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c) Respiration: Increase with mild drought but more serve drought lowers
water content and respiration.
d) Anatomical changes: Decrease in size of the cells and inter cellular
spaces, thicker cell wall , greater development of mechanical tissue.
Stomata per unit leaf tend to increase.
e) Metabolic reaction: All most all metabolic reactions are affected by water
deficits.
f) Hormonal Relationships: The activity of growth promoting hormones like
cytokinin, gibberlic acid and indole acetic acid decreases and growth
regulating hormone like abscisic acid, ethylene, etc., increases.

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g) Nutrition: The fixation, uptake and assimilation of nitrogen is affected. Since dry
matter production is considerably reduced the uptake of NPK is reduced.
h) Growth and Development: Decrease in growth of leaves, stems and fruits.
Maturity is delayed if drought occurs before flowering while it advances if
drought occurs after flowering.
i) Reproduction and grain growth: Drought at flowering and grain development
determines the number of fruits and individual grain weight, respectively. Panicle
initiation in cereals is critical while drought at anthesis may lead to drying of pollen.
Drought at grain development reduces yield while vegetative and grain filling stages
are less sensitive to moisture stress.

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j) Yield: The effect on yield depends hugely on what proportion of the total
dry matter is considered as useful material to be harvested. If it is aerial
and underground parts, effect of drought is as sensitive as total growth.
When the yield consists of seeds as in cereals, moisture stress at
flowering is detrimental. When the yield is fibre or chemicals where
economic product is a small fraction of total dry matter moderate stress
on growth does not have adverse effect on yields.

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Strategies for drought management
1. Adjusting the plant population: The plant population should be lesser
in dryland conditions than under irrigated conditions. The rectangular
type of planting pattern should always be followed under dryland
conditions. Under dryland conditions whenever moisture stress occurs
due to prolonged dry spells, under limited moisture supply.
2. Mid season corrections: The contingent management practices done in
the standing crop to overcome the unfavourable soil moisture conditions
due to prolonged dry spells are known as mid season conditions.

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3. Mulching: It is a practice of spreading any covering material on soil
surface to reduce evaporation losses. The mulches will prolong the
moisture availability in the soil and save the crop during drought
conditions.
4. Weed control: Weeds compete with crop for different growth resources
are seriously under dryland conditions. The water requirement of most of
the weeds is more than the crop plants. Hence they compete more for soil
moisture. Therefore the weed control especially during early stages of
crop growth reduce the impact of dry spell by soil moisture conservation.

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5 Water harvesting and life saving irrigation: The collection of run off
water during peak periods of rainfall and storing in different structures is
known as water harvesting. The stored water can be used for giving the life
saving irrigation during prolonged dry spells.

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Crop Management Practices
Intercropping: Intercropping refers to growing two or more crops in the
same field with specific row arrangement during the same season. In
areas where the annual rainfall is in the range of 600-850 mm,
intercropping is being recommended and practiced. The different
intercropping systems are followed in different regions of the country
based on soil, rainfall, market price and marketing facilities.
Intercropping systems are subject to change due to change in market price
of component crops. Intercropping is widely practiced in dry farming
since it offers many advantages as outlined below.

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• Intercropping is a risk minimization strategy and provides an insurance against
complete crop failure due to rainfall abnormalities.
• It provides more yield and income per unit area per unit time than sole
cropping
• Stability in production is achieved
• Multiple products for home consumption as well as for marketing are made
available
• When legumes are included in intercropping, soil fertility is enriched
• Intercrop canopy suppresses weed growth
• One crop provide physical support to other crop.

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b) Conservation tillage: The objectives are to achieve soil and water
conservation and energy conservation through reduced tillage operations. This
systems usually leave crop residue on the surface and each operation is planned
to maintain continuous soil coverage by residue or growing plants. The
conservation tillage practices may advance some of the goals of alternative
farming such as increasing organic matter in soil and reducing soil erosion, but
some conservation tillage practices may increase the need for pesticides.
Conservation tillage changes soil properties in ways that affect plant growth, and
reduce water runoff from fields.

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Agronomic practices for moisture conservation
1) Conservation tillage: The objectives are to achieve soil and water
conservation and energy conservation through reduced tillage operations. This
systems usually leave crop residue on the surface and each operation is planned
to maintain continuous soil coverage by residue or growing plants. The
conservation tillage practices may advance some of the goals of alternative
farming such as increasing organic matter in soil and reducing soil erosion, but
some conservation tillage practices may increase the need for pesticides.
Conservation tillage changes soil properties in ways that affect plant growth,
and reduce water runoff from fields.

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2) Contour cultivation (Contour farming): A line joining the points of equal
elevation is called contour. All the cultural practices such as ploughing, sowing,
intercultivation etc. done across the slope reduce soil and water loss. By
ploughing and sowing across the slope, each ridge of plough furrow and each row
of the crop act as obstruction to the runoff and provide more time for water to
enter into the soil leading to reduced soil and water loss.
3) Strip cropping: It is a system of growing of few rows of erosion resisting crops
and erosion permitting crops in alternate strips on contour (across the slope) with
the objective of breaking long slopes to prevent soil loss and runoff. Close
growing erosion resisting crops reduce the transporting and eroding power of
water by obstructing runoff and filtering sediment from runoff to retain in the
field.

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4) Mulching: Mulching of soil with available plant residues reduce soil loss
considerably by protecting the soil from direct impact of raindrop and reducing
the sediment carried with runoff .A minimum plant residue cover of 30 per cent
is necessary to keep runoff and soil loss within the acceptable limits. Vertical
mulching also reduce soil loss particularly in vertisols by increasing
infiltration.
5) Deep tillage: of 25-30 cm is beneficial for deep heavy clay soils to improve
permeability and to close cracks formed while drying. In soils with hard pans,
deep tillage once in 2-3 years with chisel plough up to 35-45 cm depth at 60-
120 cm interval will increase effective depth for rooting and moisture storage.
Deep tillage is preferable for cotton, red gram and other deep rooted crops. It is
not to be recommended for shallow, gravelly, light textured soils.

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Alternate land use systems
A pattern of land use that is different from the existing or the conventional can be
described as an alternative land use system. The term alternate land use is applicable
to all classes of land to generate assured income with minimum risk through
efficient use of available resources. The advantages of alternative land use systems
are
1. Optimising resource use by enhancing biological productivity and profitability,
2. Conserving and enhancing the quality of resource base,
3. Integrating crops (arable and pastoral) and livestock,
4. Making agriculture less dependent on off-farm inputs,
5. Generating employment potential

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Shifting cultivation: Shifting cultivation is the type of cultivation in which the
farmers cut trees and clear the land for cultivation. They also burn the
uprooted trees and mix their ashes in the soil so as to fertile the soil. After
cultivation and harvesting they move on to other land and repeat the same
process.

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Classification of drought
Drought can be classified based on duration, nature of users, time of occurrence
and using some specific terms.
1. Based on duration:
a. Permanent drought: This is characteristic of the desert climate where sparse
vegetation growing is adapted to drought and agriculture is possible only by
irrigation during entire crop season.
b. Seasonal drought: This is found in climates with well defined rainy and dry
seasons. Most of the arid and semiarid zones fall in this category. Duration of the
crop varieties and planting dates should be such that the growing season should fall
within rainy season.

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c. Contingent drought: This involves an abnormal failure of rainfall. It
may occur almost anywhere especially in most parts of humid or sub
humid climates. It is usually brief, irregular and generally affects only a
small area.
d. Invisible drought: This can occur even when there is frequent rain
in an area. When rainfall is inadequate to meet the evapo-transpiration
losses, the result is borderline water deficiency in soil resulting in less
than optimum yield. This occurs usually in humid regions.

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2. Based on relevance to the users (National Commission on Agriculture,
1976)
a) Meteorological drought: It is defined as a condition, where the annual
precipitation is less than the normal over an area for prolonged period
(month, season or year).
b) Atmospheric drought: It is due to low air humidity, frequently
accompanied by hot dry winds. It may occur even under conditions of
adequate available soil moisture. It refers to a condition when plants show wilting
symptoms during the hot part of the day when transpiration exceeds absorption
temporarily for a short period. When absorption keeps pace with transpiration the
plants revive. (Mid day wilt).

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c) Hydrological drought: Meteorological drought, when prolonged results in
hydrological drought with depletion of surface water and consequent drying
of reservoirs, tanks etc. It results in deficiency of water for all sectors using
water. This is based on water balance and how it affects irrigation as a whole
for bringing crops to maturity.
d) Agricultural drought (soil drought): It is the result of soil moisture stress
due to imbalance between available soil moisture and evapotranspiration of a
crop. It is usually gradual and progressive. Plants can therefore, adjust at least
partly, to the increased soil moisture stress. This situation arises as a
consequence of scanty precipitation or its uneven distribution both in space
and time.

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3 Based on time of occurrence
a) Early season drought: It occurs due to delay in onset of monsoon or due
to long dry spells after early sowing
b) Mid season drought: Occurs due to long gaps between two successive
rains and stored moisture becoming insufficient during the long dry spell.
c) Late season drought: Occurs due to early cessation of rainfall and crop
water stress at maturity stage
4. Other terms to describe drought
a) Relative drought: The drought for one crop may not be a drought situation for
another crop. This is due to mismatch between soil moisture condition and crop

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selection. for Eg. A condition may be a drought situation for growing rice, but
the same situation may not be a drought for growing groundnut.
b) Physiological drought: Refers to a condition where crops are unable to
absorb water from soil even when water is available, due to the high osmotic
pressure of soil solution due to increased soil concentration, as in saline and
alkaline soils. It is not due to deficit of water supply.

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Contingency cropping: Contingency cropping is growing of a suitable crop
in place of normally sown highly profitable crop of the region due to
aberrant weather conditions. In dryland agriculture, contingency of growing
another crop in place of normally grown crop arises due to delay in the onset
of monsoon.
Contingency cropping is highly location specific due to variation in amount
and distribution of rainfall. Especially in arid regions, the spatial distribution
of rainfall is highly variable.

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Contingency crop plan for different abnormalities
Rainfall abnormality Contingency plan and midterm correction
1. Delayed onset of rainfall
a) Delay exceeding-4 weeks Alternate crops of short duration to be sown
Delay in South west monsoon
Normal - June
Delay - July
Delay - August
Groundnut
Ragi / pearl millet
Cowpea
Delay in North east monsoon
Normal - October
Delay - Early November
Delay - Late November
Cotton / Sorghum
Sunflower / Pearl millet / Ragi
Coriander / Bengalgram

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b) Delay of 1 to 2 weeks Alternate varieties of short duration of same crop Eg. Sorghum Co 19
(150 days) Co 25 (110 days), Red gram local (180 days) Co 5 (130 days)
2. Early withdrawal of rainfall Antitranspirant spray, harvesting for fodder (millets), harvesting at
physiological maturity
3. Intermediary dry spell
a. Immediately after sowing Gap filling with subsequent rains if stand reduction is less than 20%. Re-
sowing if stand reduction is more than 20%, mulching between crop
rows. Stirring soil surface to create dust mulch to reduce evaporation
b. At vegetative phase Mulching, antitranspirant spray, spraying potassium chloride, thinning of
33-50 % population
c. At flowering Antitranspirant spray, harvesting for fodder and ratooning with
subsequent rains in millets (e.g sorghum)
d. At ripening Antitranspirant spray, harvesting for fodder, harvesting at physiological
maturity

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