Unit 6. SOIL-WATER-CROP RELATIONSHIP. INTRODUCTION. Both soil and water are essential for plant growth. The soil provides a structural base to the plants and allows the root system (the foundation of the plant) to spread and get a strong hold.
The three zones, beginning from the surface downward are:
Zone A :
Zone B :
Zone C :
SOIL WATER SYSTEM
According to textural gradations a soil may be broadly classified as:
• Class: there are five recognized classes in each of the primary types. These are very fine, fine, medium, coarse and very coarse.
• Grade:Grades are termed as structure less, weak, moderate, strong and very strong depending on the stability of the aggregates when disturbed.
Ratio of volume of voids to total volume of soil mass.
It varies with:
pH value of soils:
Depth of soil:
(i) Adequate storage of water (ii) root penetration & sustain relatively long periods between irrigation.
These soils are formed by successive deposition of silt transported by rivers during floods, in the flood plains and along the coastal belts.
Changing the crops to be grown in the land every year for the 3 reasons,
Usual crop rotation:
i) Wheat – great millet gram, ii)Rice-gram iii)Cotton-wheat-gram iv) cotton-wheat-sugarcane v)cotton-great millet-gram
c) Drainability : drain off excess water
d) Leachability :removal of soluble salts by passing good quality of water.
It is defined as suspended water in the uppermost belt of soil of zone of aeration lying near enough to surface to be discharged into atmosphere by transpiration of plants or by evaporation from the soil.
It includes :
Un available Water:
Soil moisture content:
The amount of water present in a soil is termed as soil moisture content, expressed as mm of water depth present in 1 m depth of soil. It is not constant but varies with time.
Permanent wilting point.