Moisture Release Pattern and Available Water Content in Normal and Sodic Clay Soils

The data collected regarding moisture release pattern and hydraulic properties suggests that the definition of upper and lower limits of soil water availability does not hold good in sodic Vertisols and even to some extent in normal clay soils. These concepts gave only rough indices in normal soils and are highly altered in sodic clay soils. The water, above and below these limits may be available to the crops in a normal clay soil whereas, in sodic clay soils, the plant growth may be retarded or plants may even die long before the so-called wilting point. Water extraction by plant roots may continue well beyond 15 bars suction in normal clay soil for survival of the plants due to its favourable hydraulic properties and micro-pore structures. The available water becomes a limitation for growing crops in sodic clay soils due to its very poor release and deteriorated pore structure. Thus the hydraulic properties of a normal clay soil are boon to rainfed/dryland farming but these become a setback when this soil turns to sodic phases.