Green Manure Species and Sowing Time Effects on the Agronomic Performance of Common Bean

An evaluation of sowing date effects on the development of green manure species and the subsequent effects on the agronomic performance of common bean (Phaseolus vulgaris L.) was conducted using three consecutive years of field trials. A randomized block design was used with a factorial treatment structure of 3 yr, three sowing dates and five green manure species {sunn hemp [Crotalaria juncea L.], slender leaf rattlebox [C. ochroleuca G. Don], velvet bean[Mucuna pruriens L.], pigeon pea [Cajanus cajan (L.) Millsp.], and jack bean [Canavalia ensiformis (L.) DC.]}, aiming to determine the agronomical performance of common bean in response to species and sowing date of different green manures. The dependent variables used to evaluate green manure development were “green manure shoot dry mass (GMSDM), green manure N accumulation (GMNA) and green manure nitrogen accumulation efficiency (GMNAE)”. For common bean “common bean leaf area index (CBLAI), common bean shoot dry mass (CBSDM), number of pods per plant (NPP), number of grains per pod (NGP), total of grains per plant (TGP), 100-grain weight (100GW), grain yield (GY), grain harvest index (GHI), and nitrogen use efficiency (NUE)” were used to evaluate common bean performance. The GMSDM and GMNA both decreased when the green manure were sown in February rather than November, with the exception of velvet bean. Although the GMNA varied with year, species, and planting date, values above 90 kg ha–¹ were common after November and December sowing and were sufficient to ensure good GY levels of subsequent common bean. Pigeon pea stood out because of its positive effect on the CBLAI, CBSDM, and NUE values of subsequent common bean. The GMNAE, NPP, NGP, NUE, and GHI were significantly correlated with GY. The best combination of these variables resulted in a common bean GY of 2000 kg ha–¹, which is 57% higher than the Brazilian average. These results indicate that the use of green manure can contribute to the sustainability of organic production systems in tropical regions.