Soil Water Matric Potential at the Surface of Germinating Gram, Cotton, Soybean and Cowpea Seeds

In laboratory studies seed surface-soil water matric potentials (SS-SWMP) of germinating gram, cotton, soybean and cowpea were determined at 8.0, 12.0 and 17.0 per cent soil water contents (θ_s). In all the four crops the values increased with the rise in time of seed-soil contact but were much lower than the matric potential of bulk soil. The SS-SWMP values were much higher at θ_s 12.0 and 17.0 per cent than at 8.0 per cent. Crop species and cultivars within a species differed in their SS-SWMP values. Gram and cotton had lower potentials than soybean and cowpea. Cultivars C-235 in gram and H-14 in cotton had lower values than the corresponding cultivars G-180 and PS-10, respectively.