Soil fertility and yield as influenced by different legume-wheat (Triticum aestivum) sequences

An experiment was conducted during 1993-95 at Ranchi on sandy loam soil low in available N and P, and medium in available K. The experiment comprised of 4 legumes, viz. soybean [Glycine max (L.) Merr.], blackgram (Phaseolus mungo L.), cowpea [Vigna unguiculata (L.) Walp.] and style (Stylosanthes hamata L.) and 1 cereal, i.e. rice (Oryza sativa L.) in kharif and followed by 5 levels of N in wheat [Triticum aestivum (L.) emend. Fiori & Paol.] in rabi with, viz. 0,25,50,75 and 100 kg N/ha. The results revealed that in blackgram plots, the soil organic carbon, available N, P and K were higher in 0-15 cm soil layer over their initial status after 2 cycles of rotation. The available soil N, P and K in other legume plots were also higher compared with rice-wheat sequence. Application of 75 kg N/ha to succeeding wheat after legume augmented available N and K in soil. The yield of wheat was markedly higher after blackgram compared with wheat after other legumes and rice. However, style-wheat system recorded the maximum wheat equivalent yield (WEY), being higher over other cropping systems. The yield of wheat and WEY increased with increasing level of N up to 75 kg/ha.