Indian Agricultural: Growth, Generation, Policy & Problem Indian Agricultural | Page 16

Pg.no. 15
called contour plowing may be used to prevent soil erosion and conserve rainfall. Researchers in
agricultural soil science also seek ways to use the soil more effectively in addressing associated
challenges. Such challenges include the beneficial reuse of human and animal wastes using
agricultural crops; agricultural soil management aspects of preventing water pollution and the build-up
in agricultural soil of chemical pesticides.
Kind of soil and their variables
Some soil variables of special interest to agricultural soil science are:
Soil texture or soil composition: Soils are composed of solid particles of various sizes. In decreasing
order, these particles are sand, silt and clay. Every soil can be classified according to the relative
percentage of sand, silt and clay it contains.
Aeration and porosity: Atmospheric air contains elements such as oxygen, nitrogen, carbon and
others. These elements are prerequisites for life on Earth. Particularly, all cells (including root cells)
require oxygen to function and if conditions become anaerobic, they fail to respire and metabolize.
Aeration in this context refers to the mechanisms by which air is delivered to the soil. In natural
ecosystems soil aeration is chiefly accomplished through the vibrant activity of the biota. Humans
commonly aerate the soil by tilling and plowing, yet such practice may cause degradation. Porosity
refers to the air-holding capacity of the soil. See also characterization of pore space in soil.
Drainage: In soils of bad drainage the water delivered through rain or irrigation may pool and
stagnate. As a result, prevail anaerobic conditions and plant roots suffocate. Stagnant water also
favors plant-attacking water molds. In soils of excess drainage, on the other hand, plants don't get to
absorb adequate water and nutrients are washed from the porous medium to end up in groundwater
reserves.
Water content: Without soil moisture there is no transpiration, no growth and plants wilt. Technically,
plant cells lose their pressure (see osmotic pressure and turgor pressure). Plants contribute directly to
soil moisture. For instance, they create a leafy cover that minimizes the evaporative effects of solar
radiation. But even when plants or parts of plants die, the decaying plant matter produces a thick
organic cover that protects the soil from evaporation, erosion and compaction. For more on this
subject see mulch.
Ramesh Kumar P