A possibility of estimating the field capacity (FC), wilting point (WP), total available water (TAW), and readily available water (RAW) of soils was investigated from their saturation percentage(SP). Regression equations were obtained from the data from 166 Nigerian soils with wide variations in texture and other physico-chemical properties. The results showed a strong linear relationship between saturation percentage and the gravimetric percentage moisture contents at FC (r=0.972, P<0.001), and WP (r=0.949, P<0.001), but a weak linear relationship with TAW (r=0.771, P<0.01) and RAW (r=0.489, P<0.05). The regression equations calculated between these soil moisture constants and SP predicted the FC and WP of 25 independent soils very well, but were not good predictors of TAW and RAW. Reliable and satisfactory estimates of TAW were obtained by subtracting estimated WP from estimated FC, and of RAW by subtracting estimated moisture content at – 100 kPa matrix potential from estimated FC.
Communications in Soil Science and Plant Analysis 04/1998; 29(7-8-7-8):913-922. DOI:10.1080/00103629809369995