Reclamation and Nutrient Management for Salt-affected Soils

Abstract

Soil salinity and soil alkalinity are two major land degradation processes in agricultural lands and both adversely affect the crop yields. The genesis of salt-affected soils and poor quality groundwater is natural process and it is influenced by parent material, mineralogy, topography and human activities. Inefficient irrigation water management including canal network losses leads to the waterlogging and soil salinity/alkalinity while use of poor quality waters for crop production without due consideration to its chemical composition and leaching requirement of soil is responsible for soil salinization and alkalization in semi-arid and arid regions. Management of such soils includes reclamation through chemical amendment; salt leaching; improved agronomic, irrigation water and nutrient practices; alternate land uses; and use of salt-tolerant varieties. Solute transport in case of alkalinity is reactive and hence addition of chemical amendment is an important requirement for its reclamation. Similarly, solute transport in saline soils is non-reactive and leaching of soil mass by good quality water is sufficient for reclamation. In case of waterlogged saline soils, leaching along with water table control in root zone is a necessity. Percentage of organic carbon and availability of different nutrients for crop production in saline and alkali soils are influenced by chemical reactions taking place at the soil exchange complex and resultant chemical equilibrium among soil solution, adsorbed and precipitated/solid phases. Lesser amount of particular cation/anion in soil solution due to excess adsorption or excess leaching creates problem of deficiency of that nutrient and crops respond to its application through fertilizer. On the other hand, excess amount of particular cation/anion in soil mass creates problem of toxicity. Nutrient management of different crops with reference to different macro- and micro-nutrients is guided by the above-mentioned soil chemical processes and is standardized through field experiments conducted at different places in India.