Cover crop and early nitrogen management for common bean in a tropical no-till system

Common bean (Phaseolus vulgaris L.) has been grown under no-till (NT), but nitrogen (N) management remains unclear when a previous cover crop is part of the farming system. In this study, we hypothesized that N applied to living cover crops, preceding the main grain crop of the rotation, can increase productivity and N-use efficiency of the grain crop. Common bean was grown after palisade grass [Urochloa brizantha (Hochst. Ex A. Rich.) R.D. Webster] and ruzigrass [Urochloa ruziziensis (R. Germ. and C.M. Evrard) Crins] cover crops combined with N management [application to living cover crops 35 days before common bean seeding (DBS), 1 DBS, conventional, and control (zero-N application)] in four experiment-years. Dry matter (DM) and N content for palisade grass was consistently greater at termination relative to ruzigrass. Nitrogen application 35 DBS increased cover crop DM, N content, and the decomposition rate relative to the other N treatments. Greater common bean yield occurred following palisade grass than ruzigrass, and N application 35 DBS increased common bean yield compared to 1 DBS and conventional in one out of four experiment-years. Only minor differences in the agronomic efficiency (AE) of applied N to cover crops were detected between 35 DBS and 1 DBS, and only for one experiment-year, when palisade grass resulted in greater AE than ruzigrass. Applying N early to living crops such as palisade grass is an alternative N management strategy to the traditional approach for N fertilization in common bean.