Effects of relay inter-cropping summer cover crops with maize on cover crop biomass and maize yields in a warm-temperate region of South Africa

Abstract

Little research attention has been given to growing summer cover crops as part of conservation agriculture systems. Three cover crops (sorghum [Sorghum bicolor], mucuna [Mucuna pruriens] and sunhemp [Crotalaria juncea]) were relay-intercropped into maize [Zea mays] 42 days after planting maize. Biomass yields, N uptake and maize yield were measured. In sole cropping, sorghum had the highest dry weight (11 t ha⁻¹) followed by sunhemp (7.2 t ha⁻¹) and mucuna (6.1 t ha⁻¹). However, cover crop biomass yields dropped significantly (85% for sorghum, 70% for sunhemp and mucuna) when relay-intercropped into maize. Nitrogen uptake followed a similar pattern with mucuna having the highest N-uptake of 70 kg N ha⁻¹ in relay-intercropping as compared to the > 250 kg N ha⁻¹ in the sole cropping system. Maize biomass and grain yields were not affected by relay-intercropping cover crops. The low cover crop biomass yields in relay-intercropping may not be viable for sustainable conservation agriculture.