||Texture and other soil properties and plant
Many of the important soil properties are related to texture. Clayey soils show high
water holding capacity, high plasticity, and stickiness and swelling whereas sandy
soils are conspicuous by the absence of these properties. The most important way
in which soil texture affects plant growth is water and with it the nutrient supply.
The available water holding capacity of soil is related to soil texture.
structure and plant growth
Soil structure influences plant growth
rather indirectly. The pores are the controlling factors governing water, air and
temperature in soil, which in turn, govern plant growth. One of the best e.g. of
the effect of soil structure on plant growth is the emergence of seedlings in the
seedbed. The seedlings are very sensitive to soil physical condition so that there
should not be any hindrance to the emergence of tender seedlings and there should
be optimum soil water and soil aeration. The soil in the seedbed should have a
structure so that the peds are soft and porous and roots of the seedling can penetrate
it easily. The hard compact layer impedes root growth.
Water is essential for plant growth.
Soil is capable of being a storehouse of water and becoming the main source of water
for land plants. Soil water plays a significant role in several natural processes-
evaporation, infiltration and drainage of water, diffusion of gases, conduction
of heat, and movement of salts and nutrients are all dependent upon the amount of
water present in soil. Plants meet their water requirement from water stored in
of crops and cropping practices on soil structure
Crops affect soil structure through
their vegetative canopy above the ground and their roots below the ground. Grasses
are conducive to well structured soil. Organic residues left by the grassroots,
root pressure, pores due to decayed roots and microbial activity in the rhizosphere
produce ideal crumb structure. The vegetative canopy protects the soil from the
beating action of rain drops and destruction of the structure of the surface soil
and prevents crusting. The role of legumes in building up soil fertility is well
known. As legumes have place in sound crop rotation practices, the beneficial effect
is usually attributed to nitrogen added to the soil by legumes.
and plant growth
Oxygen is required by microbe and
plants for respiration. Oxygen taken up and carbon dioxide evolved are stoichiometric.
Under anaerobic conditions, gaseous carbon compounds other than carbon dioxide are
evolved. Root elongation is particularly sensitive to aeration. Oxygen deficiency
disturbs metabolic processes in plants, resulting in the accumulation of toxic substances
in plants and low uptake of nutrients. Certain plants such as rice are adapted to
grow under submerged condition. These have large internal air spaces, which facilitate
oxygen transport to the roots.
Soil compaction is the process of
increasing dry bulk density of soil, reducing the pore space by expulsion of air
through applied pressure on a soil body. Soil compaction creating problems for seed
germination, water transmission and aeration. Crusting of soil is a form of soil
compaction. The crusts present a serious barrier for seedling emergence. Lowering
the exchangeable sodium percentage and incorporation of organic matter prevent crust