Field water balance and water use efficiency of soybean [Glycine max (l.) merr.] as influenced by phosphate fertilization in vertisols

Studies were carried out to evaluate the effect of different levels of phosphorus supplied through single super phosphate (SSP) and Jhabua rock phosphate (JRP) in combinations with and without farm yard manure, phosphorus solubilizing material (PSM) on the productivity, nutrient uptake, water use and water use efficiency of soybean crop grown on black clay soils. Highest seed yield of 1253 kg/ha and water use efficiency of 3.21 kg/ha/mm of soybean were recorded due to the treatment of Jhabua rock phosphate equivalent to 90 kg/ha P₂O_s applied in conjunction with 5 t/ha of FYM+3 kg/ha PSM and seed treatment with PSM (T₁₂). Next in order were the treatments SSP-P₆₀ (T₂), JRP-P₆₀+5 t/ha FYM+10 g PSM/kg seed treatment+3 kg PSM blended with 50 kg FYM/ha (T₁₁), JRP-P₉₀+5 t/ha FYM+10 g PSM/kg seed treatment (T₁₀) and JRP-P₆₀+5 t/ha FYM+10 g PSM/kg seed treatment (T₉), respectively, which resulted in seed yield of 1185, 1175, 1166 and 1136 kg/ha, respectively, and the differences were statistically non-significant in between them. N, P, K and S content in soybean seeds varied from 5.64 to 6.11,0.116 to 0.394, 1.40 to 2.22 and 0.311 to 0.457%, respectively. The treatments where both, PSM and FYM, were applied with JRP either @ 60 kg P/ha or @ 90 kg P/ha, good responses were observed with respect to crop yield, nutrient uptake and water use efficiency suggesting beneficial effects of PSM and FYM application. Highest water use efficiency of 3.21 kg/ha/mm by soybean was found due to the treatment T₁₂ (90 kg P/ha through JRP+seed inoculation by PSM+blended PSM+FYM). The results of this study lead to conclude that treatments involving PSM and FYM tended to increase the water use and water use efficiency and seed yield too.