Residual effect of green manuring and phosphorus on productivity of wheat in rice-wheat system

Abstract:

Continuous rice-wheat cropping without legume inclusion steadily depletes soil phosphorus reserves and organic matter. This research quantified the residual effect of three green manure species (Sesbania aculeata, Crotalaria juncea, Sesbania cannabina) incorporated during the rice phase, combined with four phosphorus levels (0, 30, 60, 90 kg P₂O₅/ha), on the succeeding winter wheat crop at the Holstein College of Dairy Sciences, Kiel, Germany, over two rotation cycles (2019-20 and 2020-21). A split-plot design placed green manure in main plots and P levels in sub-plots with three replications. Wheat grain yield under Sesbania aculeata residues + 60 kg P₂O₅/ha reached 4.92 t/ha 38.2% above the no-green-manure control at the same P rate. Residual soil available P (Olsen-P) after wheat harvest was 19.4 mg/kg in the best treatment versus 11.7 mg/kg in controls. The research confirms that incorporating a fast-decomposing legume before rice can carry meaningful fertility benefits into the following wheat crop.