Effects of nitrogen levels and crop arrangements on the incidence of Megalurothrips sjostedti Trybom and Maruca vitrata Fab in maize/cowpea intercrop

Abstract

Four nitrogen levels (0, 20, 30 and 60 kg N/ha) and five crop arrangements were evaluated for their effects on the incidence of Megalurothrips sjostedti and Maruca vitrata and on the grain yield of maize (Zea mays L.) andcowpea (Vigna unguiculata Walp). The crop arrangements were one row of maize alternating with one row of cowpea (1:1 inter-row alternate arrangement), one row of maize alternating with two rows of cowpea (1:2 inter-row alternate arrangement) and two stands of maize alternating with two stands of cowpea along the same row (2:2 intra-row alternate arrangement). The other two crop arrangements were the sole maize and sole cowpea control treatments. Nitrogen levels were assigned to the main plots while crop arrangements were assigned to the sub-plots in a split-plot design. Populations of Megalurothrips sjostedti and Maruca vitrata were significantly affected by crop arrangements. In most cases the 1:1 inter-row alternate arrangement gave the lowest population of these insects. The interaction effects of nitrogen levels and crop arrangements were significant in the case of both thrips and pod borers (Maruca vitrata). The yields of both maize and cowpea were affected significantly by the crop arrangements, with sole maize and sole cowpea recording the highest grain yields.