Sustainability and agro-monetary return in beet–immature cowpea intercropping as a function of green manuring and population density

One of the questions that have been asked about the intercropping of beet with immature cowpea is how to properly use green manuring and population density of the component crops and their interaction for system sustainability. The objective of this study was to evaluate the agro-monetary benefits and sustainability of intercropping beet and immature cowpea under the influence of green manure with Merremia aegyptia and Calotropis procera and the cowpea population density in a semi-arid environment during two years of cultivation. The experimental design was randomized blocks, with treatments arranged in a 4×4 factorial scheme with 4 replications. The first factor of this scheme consisted of equitable amounts of M. aegyptia and C. procera biomass at doses of 20, 36, 52 and 68 t ha−1 on a dry basis, and the second factor was cowpea population density, with 80, 120, 160 and 200 thousand plants ha−1. The cowpea and beet cultivars planted were ‘BRS Tumucumaque’ and ‘Early Wonder’, respectively. The greatest agro-economic advantages of beet × immature cowpea intercropping were achieved with a productivity index system of 35.37 t ha−1, land equivalent coefficient of 0.35 and monetary equivalence ratio of 1.79, respectively, in the combinations with equitable biomass amounts of the green manure of 62.19, 62.07 and 61.63 t ha−1 and a cowpea population density of 142 thousand plants ha−1.