Comparison of soil organic carbon pools, microbial activity and crop yield and quality in two vegetable multiple cropping systems under mediterranean conditions

© 2019 Elsevier B.V.The use of legumes in multiple cropping may play an important role in nutrient cycling as it has an impact on organic matter dynamics and biological activity in the soil, although its effects depend on the specific plant species included in the multiple cropping. Organic management is in addition expected to decrease the negative impacts of conventional intensive farming through enhancements of the soil C sequestration and activation of microbial populations. Thus, the aim of this study was to compare the effect of different cultivars of two legume species (cowpea ¿unusual in the study area- and faba bean ¿traditional in the study area) on soil C and pools, soil N, soil enzyme activities, and crop yield and quality of subsequent vegetable crops (broccoli and melon, respectively) grown under conventional or organic systems after two crop cycles. A comparison of a broccoli monoculture, a broccoli crop grown after cowpea (multiple cropping), a melon monoculture and a melon crop grown after faba bean (multiple cropping) showed that the broccoli/cowpea system was significantly more effective for increasing soil organic C (SOC), N and soil enzyme activities than melon/faba bean multiple cropping. In the cowpea/broccoli cropping, organic management contributed to the highest C sequestration. In the faba bean/melon cropping, conventional management practice led to the highest SOC and crop yield. In addition, the faba bean/melon cropping under organic management practice increased fruit length and sugar content respect to conventional management. The legume cultivar significantly affected soil N and dehydrogenase activity. Hence, the use of cowpea in multiple cropping with non-legume vegetables seems to be a sustainable option under semiarid conditions, since it improves soil microbial activity as a result of a higher C and N rhizodeposition. The use of faba bean can enhance melon quality, and so, obtain a higher income in the organic food market.