Nitrogen Management for Common Bean After Forage Grasses Under No-till System.

Perennial forage grasses inclusion in no-till system, by intercropping them with grain crops has been an interesting alternative to provide satisfactory soil cover, keeping the system sustainability and increasing subsequent crop yield. In this system, some farmers have applied nitrogen (N) on cover crop early, several days before desiccation, aiming at N supply for the subsequent crop, including common bean (Phaseolus vulgaris L.). The objective was to evaluate the effect of N fertilization management forms on common bean crop grown under a no-till system after perennial forage grasses, implanted intercropped with corn. An experiment was carried out in Botucatu, São Paulo State, Brazil, during two agricultural years. A randomized block design, with split-plots scheme and four replications was used. Plots comprised two cover crops (Brachiaria brizantha (Hochst. ex A. Rich) Stapf – cv. Marandú and Panicum maximum Jacq. – cv. Mombaça) and subplots comprised six N management forms (0-0 (control), 100-0, 70-30, 50-50, 30-70, and 0-100 kg ha^-1 of N, broadcasted on the surface 19 d before cover crops desiccation or side-dressed on common bean (third-fourth trifoliate leaf expanded), respectively). Common bean cv. Pérola was sown 14 d after cover crops desiccation in 2007-2008 and 20 d in 2008-2009. Nitrogen source was ammonium sulfate. Nitrogen application, mainly on side-dressing, increased N concentration in common bean leaves. Pods per plant and grain yield of common bean were increased by N fertilization. In 2008-2009 common bean grain yield was higher in succession to P. maximum. Nitrogen application increased 15.3% common bean grain yield on average in 2007-2008 and 21.0% in 2008-2009. Early N application in cover crop did not interfere significantly in common bean grain yield, when compared with side-dressing application.