Effect of Intercropping Sonchus oleraceous with Maize and Cowpea on Biomass and Soil Conservation for Growth and Yield

Maize and cowpeas are important staple foods in Kilifi county and their productivity is highly constrained by increased incidences of pests, weeds and prolonged drought. These adversely affect maize yields and availability of cowpea leafy vegetables during the dry seasons. Sonchus oleraceaous, a common weed in most maize-cowpea cropping systems is widely used and most preferred in most households of the Kenyan coast as a leafy vegetable. However, its role as a vegetable and cover crop have not been exploited and or documented. This study was conceived to investigate the effects of Sonchus on maize-cowpea cropping systems, specifically as a cover crop. A randomized complete block design experiment replicated thrice was set at Pwani University Crop Science farm for two (2) cropping seasons in 2014 to 2016. Treatments included three (3) intercropping systems composed of maize, Sonchus and cowpeas, and the sole crops as a control with maize spacing of 90 by 60 and cowpea and Sonchus at 15cm by 60cm. Plant height, % ground cover, and biomass yields were determined for each treatment. High groundcover was observed in all the intercrops, and was highest where cowpea was part of the treatment. Biomass of Sonchus was highest in the sole crop, followed by the maize-Sonchus intercrop (>7.5tons/ha) and was lowest (2.5-2.78) in the Sonchus-cowpea intercrop (82-84% lower compared to the other treatments). The results showed that intercropping maize with Sonchus was feasible where in between space was sufficient. The implication is that Sonchus can be integrated in maize farming systems for crop diversification as a vegetable to maximize on land productivity and contribute to nutrition. Further research on spacing and density for maize and Sonchus intercrop should be carried out to develop an agronomic package that would ensure maximum returns for promotion to farmers.