Agriculture Reference
In-Depth Information
reduction per unit increase in salinity than under low fertility. On the contrary,
the soils having balance nutrients can minimize the effect of salinity than the
unbalanced one.
The effects of soil texture and structure are revealed through their influence on
the infiltration capacity. For the same evapotranspiration rate, a sandy soil will lose
proportionately more water than a clay soil, resulting in a more rapid increase of
soil solution concentration. If good irrigation practices are followed, the sandy soil
will have to irrigate more frequently, thereby reducing the damage which may be
caused by increased concentration. The infiltration capacity of a field is an extremely
variable parameter and is a function of soil texture and structure. This variability is
largely responsible for the variability of soil salinity.
8.2.2.5 Climate
Three elements of climate - temperature, humidity, and rainfall - may influence
salinity response, out of which temperature is the most critical. High temperatures
increase the stress level to which a crop is exposed. This may be due to increased
transpiration rate or because of the effect of temperature on the biochemical trans-
formation in the leaf. The increase in the stress level results in changes in the salinity
response function.
High atmospheric humidity tends to decrease to some extent the crop stress
level, thus reducing salinity damage. High rainfall dilutes the salt concentration and
increases leaching, thus reducing the salinity level.
8.2.3 Mechanism of Salinity Hazard
It is interesting to know what causes the problem with plant growth when salt is
present in the soil solution. When plants take in water, nutrients are also present
in the water and are taken up. Plants naturally have salt present in their rooting
systems which pull water into the plant from the difference in osmotic pressure.
Salt in the soil solution decreases the osmotic potential of the system and slows or
even stops the uptake of water. As the difference in concentration decreases, the
osmotic potential decreases. When the concentration of salt in the soil increases and
approaches that of the plant attempting to grow, the osmotic potential decreases.
As the osmotic potential decreases, the movement of soil solution into the plant
decreases. Salt-sensitive plants basically perish from water deprivation. The plant
will express symptoms of drought even though the soil is saturated with water. The
water is present but is unavailable to the plant.
8.2.4 Salt Balance at Farm Level
From the principle of conservation of mass,
Total salt inflow into the soil system
total salt outflow from the soil
= change in salt content in soil
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