Soil conservation measures – agronomic measures of soil conservation

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Soil conservation measures – agronomic measures
of soil conservation
7.1 Definition of soil conservation
Soil conservation is using and managing the land based on the capabilities of
the land itself involving application of the best management practices leading to
profitable crop production without land degradation.
7.2 Control of water erosion
Water erosion occurs simultaneously in two steps: detachment of soil
particles by falling raindrops and transportation of detached particles by flowing
water. Hence preventing the detachment of soil particles and their transportation can
minimize water erosion. Principles of water erosion control are
– Maintenance of soil infiltration capacity
– Soil protection from rainfall
– Control of surface runoff and
– Safe disposal of surface runoff
For a sound soil conservation programme every piece of land must be used in
accordance with the land capability classification.
7.2.1 Measures of water erosion control
1. Agronomic measures
2. Mechanical measures (Engineering measures)
3. Forestry measures
4. Agrostological measures
7.2.2 Agronomic measures of soil conservation
In soil and water conservation programmes agronomic measures have to be
considered in co-ordination with others for their effectiveness. These measures are
effective in low rainfall areas particularly in fairly erosion resistant soils having
gentle slope (< 2 %).
The different agronomic measures include
1. Land preparation
2. Contour cultivation
3. Choice of crops
4. Strip cropping
5. Crop rotation / cropping systems
6. Cover crops
7. Mulching
8. Application of manures and fertilizers
9. Application of chemicals
a) Land preparation: Land preparation including post harvest tillage influence
intake of water, obstruction to surface flow and consequently the rate of erosion.
Deep ploughing or chiseling has been found effective in reducing erosion. Rough
cloddy surface is also effective in reducing erosion.
b) 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 (Fig 7.1).
Fig 7.1 Contour Cultivation
c) Choice of crops :Row crops or tall growing crops such as sorghum, maize, pearl
millet etc.,are not effective in conserving soil as they expose majority of the soil and
hence they are known as erosion permitting crops. Where as close growing crops
such as cowpea, groundnut, green gram, black gram etc., which protect soil are
known as erosion resisting crops as they are very effective in reducing soil loss by
minimizing the impact of rain drop and acting as obstruction to runoff.
d) 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. The width
of the erosion permitting and erosion resisting crops vary as per the slope of the
field. The strip cropping resembles the intercropping.
Width of crops (m)
Slope (%)
Erosion resisting Erosion permitting
Up to 1% 9.0 45.0
1 to 2% 6.0 24.0
2 to 3% 4.0 12.0
With increase in per cent slope of the soil, the width of erosion permitting and
erosion resisting crops decreases. The normal ratio between the erosion resisting
crops and erosion permitting crops is 1: 3. Among the different crops the antierosion value of pillipesara is highest, where as cotton crop recorded the lowest
value .The strip cropping is divided into four types as follows
i) Contour strip cropping: The erosion permitting crops and erosion resisting crops
are grown in alternate strips along the contours.
ii) Field strip cropping: Alternate strips of erosion permitting crops and erosion
resisting crops are raised across the general slope not necessarily on exact contour
iii) Wind strip cropping: Strip cropping of erosion permitting and erosion resisting
crops across the direction of the most prevailing wind irrespective of the contour.
iv) Buffer strip cropping: this type of strip cropping is practiced in areas having
steep slopes and badly eroded soils where strips of permanent cover crops or
perennial legumes or grasses or shrubs are alternated with field crops.
The strip cropping is simple, cheap and effective soil conservation practice
and can be adopted by the farmers.
e) Crop rotation / cropping system: Monocropping of erosion permitting crops
accelerates soil and water loss year after year. Intercropping of erosion permitting
crops and erosion resisting crops or their rotation has been found effective for
reducing soil and water loss. Inclusion of legumes like lucerne in crop rotation
reduces soil loss even in soils having 13% slope.
f) Cover crops: Good ground cover by canopy gives the protection to the land like an
umbrella and minimize soil erosion. Besides conserving soil and moisture, the cover
crops hold those soluble nutrients, which are lost by leaching. The third advantage of
the cover crops is the addition of organic matter. The legumes provide better cover
and better protection. Among the legumes cowpea has been found to produce
maximum canopy followed by horsegram, green gram, black gram and dhaincha.
g) 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.
h) Application of manures and fertilizers : Organic manures besides supplying
nutrients improve soil physical conditions thereby reduce soil loss. Fertilizers
improve vegetative canopy, which aid in erosion control.
i) Use of chemicals: Breakdown of aggregates by the falling raindrops is the main
cause of detachment of soil particles. Soils with stable aggregates resist breakdown
and thus resist erosion. Aggregate stability can be increased by spraying chemicals
like poly vinyl alcohol @ 480 kg/ha (rate will depend on the type of soil). Soils
treated with bitumen increase water stable aggregates and infiltration capacity of the