Sequential cropping effects of vegetable cowpea on cassava in cassava-cowpea intercrop, Umudike, southeast Nigeria

Abstract

Objective: A field crop experiment was conducted in 2015 and 2016 cropping seasons with the aim of quantifying the effect of sequential planting of vegetable cowpea on crop growth, yield and productivity of component crops in cassava and cowpea intercrop as well as to assess the nutrient status of the soil at harvest. Materials and Methods: The treatments comprised of four cassava cultivars intercropped with vegetable cowpea grown using sequential method in the system (NR 8082//cowpea, TMS 30572//cowpea, TME 419//cowpea, TMS 98/0505//cowpea) and their respective mono-crops. The experiment was laid out in a randomized complete block design with three replications at Umudike (05°29’N, 07E33’E, 122 m.a.s.l.), Southeastern Nigeria. In the systems, intercropping exhibited lower values in all the plant variables evaluated compared with their respective mono-cropped component crops in the plots. Results: The findings showed that there was a higher degree of complementarity between cassava and cowpea and also increased nutrient status of the soil in cowpea sown plots at harvest. The productivity indices indicated that NR 8082//cowpea intercrop exhibited highest total land equivalent ratio (LER), land equivalent coefficient and %-land saved compared to other mixes. However, financially TMS 98/0505//cowpea intercrop was more productive with the highest total gross monetary return, net return (NR) and benefit cost ratio (BCR) relative to the other treatments in the systems. The sequence of BCR in the mixes was in the order: TMS 98/0505//cowpea>NR 8082//cowpea>TMS 30572//cowpea>TME 419//cowpea. Conclusion: The regression relationships between BCR and total crop yield and between LER and %-land saved were linear and positive. Therefore, sequential cropping of vegetable cowpea in cassava intercrop exhibited strong and positive impact on the productivity of the system.