Input for Agriculture

Gypsum Valuable Input for Agriculture
By Sarvesh Shah

India ranks second on the basis of population in the world. Agricultural land utilised by the burgeoning population, the cultivable land resource is shrinking day by day. To meet the food, fibre, fuel, fodder, and other needs of the growing population, the productivity of agricultural land has to be increased rationally. This requires the use of all resources judiciously. In India, the mineral gypsum is mostly used in the manufacture of cement, fertiliser, plaster of Paris, ceramics and distemper. Smaller quantity is used as soil conditioner, for carving and statuary purposes. India has huge resources of natural gypsum of the order of 1120 million tonnes, of which recoverable reserves are estimated at 237 million tonnes. Over 95 per cent of the natural gypsum come from Rajasthan.

Gypsum is chemically calcium sulfate dihydrate (CaSO4.2H2O). When dissolved in water, it yields calcium ions (Ca2+) and sulfate-sulfur ions (SO42-). Both of these ions are essential major nutrients for growing plants. In addition to this, calcium also plays a vital role in establishing and maintaining good chemical balance in soil, water and plants. Gypsum is one of those rare materials that perform in all three categories of soil treatment: an amendment, conditioner, and fertilizer. The usage of gypsum in agriculture can be grouped into following heads:

Reclaims soil sodicity: The sodic soils have exchangeable sodium percentage (ESP) more than 15, it must be lowered for soil improvement as well as better crop growth. The calcium supplied by gypsum replaces the sodium held at the clay-exchange sites. The replaced sodium can be leached from the soil as sodium sulfate to an appropriate sink.

Decreases the toxic effect of NaCl salinity: Calcium from gypsum has a physiological role in inhibiting the uptake of sodium by plants. Thus plant are mitigate the sodium toxicity, which is more pronounced in the salt affected soils.