Abstract

                                The present study was carried out to estimate the available water capacity of 130 soil samples collected from different districts of Tamil Nadu. The samples were analysed for field capacity at 1/3 bar pressure and permanent wilting point at 15 bar pressure in Pressure Membrane Apparatus besides, organic carbon and texture (particle size). The moisture retention at field capacity ranged from 6.8 % to 57.9 % and at permanent wilting point the moisture content ranged from 2.4 % to 38.0 %. The available water capacity (moisture retained between 1/3 bar and 15 bar pressure) varied from 1.2 % to 22.6 % with a mean value of 13.5 %. The soil parameters viz., organic carbon, clay, silt and sand significantly influenced the field capacity of soils with a r 2 value of 0.7386. Similar effect was recorded for permanent wilting point (r2 =0.7258). Also regression equations were derived for calculating field capacity, wilting point and available water capacity from the value of organic carbon and textural constituents.

Key words : soil moisture retention, soil texture, pressure membrane apparatus.