Evaluation of Cowpea Plant Density and Nitrogen Fertilizer for Productivity of Sorghum/Cowpea Intercrops at Abergelle, Northern Ethiopia

Abstract

As mono cropping practice limited sorghum productivity in Abergelle, an experiment on sorghum/cowpea intercropping was conducted in 2014 cropping season to evaluate the effect of density of the intercropped cowpea and nitrogen fertilizer rates on yield and yield related traits of sorghum and cowpea as well as to determine the appropriate plant density of cowpea and nitrogen fertilizer rate that maximize the productivity of the intercrop system. Treatments consisted of factorial combinations of three cowpea densities (50, 75 and 100%) and four levels of nitrogen rates (0, 20.5, 41 and 61.5kg N ha^-1) accompanied with sole sorghum and sole cowpea were carried out in Randomized Complete Block Design (RCBD) with three replications. The analyzed result showed that grain yields of the component crops were highly significantly affected (P<0.01) due to interaction effect. The highest grain yield of sorghum (1769.10 kg ha^-1) and cowpea (975.67 kg ha^-1)  was obtained from the combination of 61.5 kg N ha^-1 with 100% sole cowpea plant density and when 41 kg N ha^-1 combined with 75% of sole cowpea plant density, respectively. The land equivalent ratio (LER) and gross monetary value (GMV) showed that sorghum/cowpea intercropping was highly superior to and more advantageous over sole cropping. The highest values of LER (1.76) and GMV (14313.20 ETB ha^-1) were obtained from combination of 41 kg N ha^-1 and 75% cowpea plant density. This is, therefore, combination of 41 kg N ha^-1 and 75% sole cowpea plant density can be recommended for farmers of the study area to improve sorghum productivity and the cropping system at large.

Keywords: Cowpea, Intercropping, Nitrogen, Plant population, Sorghum