Cover crops mixtures with more legumes maximize biomass and N input in irrigated fruit crops in Brazil

Abstract Cover crops, especially legumes, can counterbalance the depletion in soil organic matter, the low supply of nitrogen from the organic reserves and the losses of the inorganic fertilizers in irrigated fruit crops. We tested two cover crop mixtures, one with more and the other with less legume proportions, and one treatment where the spontaneous weeds were left to grow, before planting melon or intercropping in a mango orchard. Biomass of the cover crops and the weeds were cut and incorporated or left on the soil surface. In general, incororation or surface placement did not significantly differ. The average biomass productions of the cover crop mixtures over the three cycles were higher than that of the spontaneous weeds. They also acumulated more N, especially the mixture with more legumes (222 and 159 kg ha− 1 versus 60 kg ha− 1 in the weeds), about half of which came from symbiotic fixation (110 and 77 versus 55 kg ha− 1). These amounts are of the same order as those exported with the fruits. Thus, cover crops, especially those with high legume proportions, are a recommended practice, which should be adopted by producers and fostered by public policies, in semiarid regions.