Cover Crops Biomass N Credit for Rainfed Wheat Production.

Legumes used as cover crops to enhance soil fertility and improve crop production are often limited by phosphorus (P) deficiency. The evaluate the effects of P fertilization of substituting leguminous cover crops for nitrogen (N) fertilizer and their effects on soil fertility for rainfed wheat (Triticum aestivum, L. cv. Inqalab 91) production were investigated for successive years. A randomized complete block design with Sesbania (Sesbania aculeata Linn), Rice bean (Vigna umbellate Thunb), Cluster bean (Cyamopsis tetragonaloba L.) and a fallow treatment were factored into 0, 30, 60, and 90 kg P₂O₅ ha^-1 treatments. Treatments were replicated thrice in 8 x 6 m² field plots. Sixty days after planting, the cover crops were mowed down two weeks prior to planting wheat as a succeeding crop. The fallow designated as a chemical fertilizer treatment received 90 kg N, P₂O₅ and K ha^-1, respectively. Biomass production, N concentration, and labile fraction of cover crops were measured. Results showed that P fertilization and type of cover crops had significant interaction on biomass production, labile fraction, and biomass N concentration of cover crops .Phosphorus fertilization at ³ 60 kg P₂O₅ ha^-1 for Sesbania as preceding cover crop significantly improved the growth and yield of succeeding wheat over chemical fertilizer and other cover crops treatments. Linear contrast has shown that cover crops significantly improved rainfed wheat production than chemical fertilization.