Evaluating crop yields, crop quality and soil fertility from organic and conventional farming systems in South Africa’s southern Cape

Abstract

Climate change, water scarcity and degraded soils jeopardise the ability of agriculture to ensure food security. The dependence on agrochemicals and monoculture practices in agriculture is not only environmentally destructive and expensive; these practices also produce foods of poor nutritional value. Here we report on the initial results of a long-term comparative controlled experiment at the NMMU Saasveld campus in George to test the differences in yield and nutritional quality of crops grown under different agricultural practices. A baseline study showed considerable variation in the soil fertility of the experimental site. As anticipated from the soil analysis results, the baseline crop had varying growth from one replication to the other. Initial organic treatment yields were lower and initial nutritional levels were inconclusive. The experimental site accommodates a randomised complete block design with four replications for three agricultural treatments: conventional, organic and controlled. The crops included cabbage ( Brassica olaracea, var. capitata L. ), sweet potato ( Ipomea batatas ) and cowpeas (Vigna unguiculata). Our results show that the cabbage and cowpea yields grown under organic conditions were 20% and 24% less than conventional yields, respectively.