Intercropping organic melon and cowpea combined with return of crop residues increases yields and soil fertility

The growth of legumes, reduced tillage and addition of crop residues can be regarded as a good alternative in intercropping systems to increase soil organic matter, soil fertility and biodiversity while enhancing crop production and reducing the use of fertilizers. Despite the potential benefits, there is still a research gap about using the combination of cowpea and melon in intercropping to increase productivity and reduce external inputs. Thus, the aims of this study were to: i) assess if crop yield, crop quality and soil physicochemical properties can be improved by intercropping systems between melon (Cucumis melo L.) and cowpea (Vigna unguiculata (L.) Walp.) with reduced tillage and addition of crop residues, compared with a melon monoculture with intensive tillage and removal of crop residues, all grown under organic management; and ii) evaluated if cowpea grown as intercrop with fertilization reduced by 30% in the diversified plots can partially replace the use of fertilizers with no negative effects on total crop production. In this study we compared over three crop cycles monocrops with three different melon-cowpea intercropping patterns: mixed intercropping, row intercropping 1:1 (melon:cowpea) and row intercropping 2:1 (melon:cowpea). Our results, presented in this study, showed that intercropping systems, regardless of the pattern, kept soil organic C levels, while it significantly decreased in melon monoculture. Intercropping also significantly increased soil total N, available P and exchangeable K (0.13%, 62 mg·kg^-1 and 387 mg·kg^-1, respectively), compared to the melon monocrop (0.11%, 25 mg·kg^-1 and 306 mg·kg^-1). Total crop production was significantly higher under diversified systems, with land equivalent ratios > 1. Hence, the introduction of cowpea associated with melon, combined with reduced tillage and the incorporation of crop residues could be considered as a feasible strategy for sustainable agriculture, with environmental gains and economic savings for fertilizers and water.