Crop Yields and Phosphorus Recovery in Soybean-Wheat Cropping System on a Typic Haplustert under Integrated Use of Manure and Fertilizer Phosphorus

In field experiments with soybean-wheat cropping system conducted during 1992–93 and 1993–94 on a Typic Haplustert, soybean seed yield increased significantly with FYM application up to 4 t ha⁻¹ in 1992 and 16 t ha⁻¹ in 1993. Fertilizer P up to 44 kg ha⁻¹ also progressively improved soybean yield in both the years. Conjoint use of 16 t FYM + 44 kg P ha⁻¹ gave the highest soybean yield. The yield of following wheat crop in both the years increased significantly under the treatment in which the previous crop of soybean received FYM up to 16 t ha⁻¹ and of fertilizer P up to 44 kg ha⁻¹. Integrated use of 16 t FYM (to soybean) + 44kg P ha⁻¹ (to both soybean and wheat) produced the maximum wheat grain yield. Phosphorus uptake by soybean and wheat and available P in the post-harvest soil increased significantly with increasing rates of both FYM and fertilizer P. Averaged over two years, apparent phosphorus recovery (APR) by soybean-wheat system from fertilizer-P ranged from 24.9 to 15.1%, the lower APR being at higher P levels. With FYM applied at 4, 8 and 16 t ha⁻¹, crops recovered about 96, 66 and 45% of manure-P (5.5, 11.0 and 22 kg P ha⁻¹), respectively. In combination with FYM, fertilizer P recovery was greater at all P rates as compared to those with no manure.