Effect on intra-annual rotations with legume species on horticultural production and soil quality

Résumé

In this study we assessed the effect of preceding legumes (cowpea: Vigna unguiculata) oncrop production and soil quality in subsequent non-legumes crops (broccoli: Brassicaoleracea) during three crop years. We also assessed if cowpea cultivars (Feijão frade de fiopreto and Feijão frade de fio claro) and management practices (conventional and organic)significantly influenced crop and soil properties. The study was randomly designed in blockswith four replications, in plots of 10 m2. Soil samples (0-30 cm) were collected from eachplot at the end of the crop cycle to measure biochemical and chemical parameters in soil.Crop production and quality were determined at the end of the cycle. In cowpea, afterthree crop years and considering cultivar and management practice, we observed asignificant increase in nitrogen and phosphorus content, together with a significantdecrease in sodium and potassium content. Nitrogen was positively correlated with carbon(R > 0.65, P < 0.01) and phosphorus content (R > 0.79, P < 0.01 ), while this was negativelycorrelated with dehydrogenase activity (R > 0.74, P < 0.01 ). Soil parameters in broccoli cropdid not follow a clear pattern. There were no significant differences in crop production andquality for the subsequent broccoli crop compared to broccoli in monocrop. These resultsdemonstrated that the inclusion of cowpea in rotation significantly affected the amount ofnitrogen and phosphorus, however, this grain legume did not lead to increased cropproduction and quality in the broccoli crop.