Relay-intercropping of sunnhemp and cowpea into a smallholder maize systemin Zimbabwe

The rising real prices of purchased inputs is driving smallholder maize (Ze a mays L.) production towards lower levels of inorganic fertilizer. Legume intercrops are a source of plant N that can be produced locally and offer a practical complement to inorganic Fertilizers. Field experiments conducted on a loamy sand (Typic Kandiustalf) soil evaluated the impact of relay-int ercropping two legume crops, cowpea (Vigna unguiculata L.) and sunnhemp (Cr otolaria juncea L.) into smallholder maize in Zimbabwe. The objectives were to quantify: (i) biomass and N yield of intercropped legumes, (ii) the imp act of the legumes on companion maize yield and N uptake, and (iii) the res ponse of a subsequent maize crop to legumes. Dry matter yield ranged from 0 .6 to 4.6 Mg ha(-1) for cowpea and 0.9 to 2.9 Mg ha(-1) for sunnhemp, over two years. At the most, cowpea and sunnhemp produced 154 and 82 kg N ha(-1) , respectively. Companion maize grain yields were not reduced when the legu mes were relay-intercropped into maize fertilized at 0 to 60 kg N ha(-1). H owever, maize yields were reduced 18 to 31% when maize + legume intercrops were fertilized at 120 kg N ha(-1). In the subsequent year, maize gain yiel ds were increased by 8 to 27% following maize + legume when no fertilizer N was applied, compared with maize following maize. Legumes reduced fertiliz er needs of a subsequent maize crop by 36 kg N ha(-1). Intercropped annual legumes and small amounts of inorganic Fertilizer offers a strategy to meet the N needs on smallholder farms.