Comparing legumes for use in multiple cropping to enhance soil organic carbon, soil fertility, aggregates stability and vegetables yields under semi-arid conditions

Abstract Including legumes in rotation systems may be regarded as a sustainable way to improve soil quality and fertility for subsequent crops. Improvements in soil quality depend on inherent soil properties, climatic conditions, adopted management practices, type of fertilization (organic, chemical, legumes or biological). Hence, the aim of this study was to compare the effect of two legume species (cowpea and fava bean) on soil organic carbon (SOC), total nitrogen (Nt), NO 3 − , NH 4 + , available P, soil aggregate stability and the subsequent yields of two vegetable crops (broccoli and melon) grown under conventional or organic systems after two multiple cropping cycles. A comparison of a broccoli monoculture, broccoli grown after cowpea (multiple cropping), a melon monoculture and melon grown after fava bean (multiple cropping) showed that the broccoli/ cowpea double cropping was significantly more effective for increasing SOC and Nt than melon/fava bean double cropping. For the cowpea/broccoli multiple cropping, conventional management contributed to increasing SOC and Nt, while organic management increased available P, aggregate stability and crop yield, although this effect was cultivar dependent. The effect of management practice was not significant for the fava bean/melon except as regard crop yield, the melon yield being greater than monocrop under conventional management. Thus, the use of cowpea in multiple cropping was better for increasing SOC, soil fertility and crop yield of the subsequent crop than the use of fava bean, probably due to rhizodeposition processes. Hence, this crop could regarded as a viable alternative for sustainable crop production under semi-arid conditions.