Effect of Maize+Cowpea Intercropping on Quality Characteristics and Residual Nitrogen Availability

Abstract

The study explores two major challenges in agricultural production the efficient management of nitrogen and the spatial arrangement of crop species. Its relevance lies in simultaneously investigating these factors, providing evidence that contributes to improved nitrogen use efficiency. The results highlight the importance of adopting appropriate cropping practices and nutrient sources to enhance nutrient use and grain quality. A two-year field study was conducted in the Central Plain Zone to evaluate the effects of maize+cowpea intercropping patterns and nitrogen management practices on crop quality characteristics and residual soil nitrogen availability. The experiment, laid out in a Split Plot Design, compared four intercropping patterns viz., Sole Maize, Sole Cowpea, Maize + Cowpea (1:1), and Maize + Cowpea (2:1) in combination with five nitrogen management regimes involving different levels of the Recommended Dose of Nitrogen (RDN) supplemented by foliar applications of Nano Urea. Intercropping maize with cowpea significantly enhanced overall system productivity and improved soil nitrogen status, primarily due to the biological nitrogen fixation potential of cowpea and better resource complementarity between component crops. It appears that the 1:1 ratio of maize and cowpea significantly enhances nitrogen in the soil. This finding is crucial in reducing the application of N fertilizer on the succeeding crop. The Maize + Cowpea (1:1) intercropping system was the most effective spatial arrangement for soil enrichment, recording the highest residual soil available N (216.42 kg/ha), and showing a numerical increase in maize grain protein content. Conversely, sole cropping maximized the N and protein content of the individual crops, with Sole Cowpea achieving the highest pod protein (19.51%), confirming that interspecific competition reduced cowpea quality under intercropping. Regarding nitrogen management, the application of 100% RDN consistently yielded the highest nutrient and protein content in both maize and cowpea. However, the treatment of 75% RDN supplemented with foliar Nano Urea at 30 and 50 DAS was statistically comparable to 100% RDN for all key quality parameters and residual soil N (206.21 kg/ha). This demonstrated that strategic use of Nano Urea enhances N use efficiency, allowing for a 25% reduction in conventional urea fertilizer without compromising system performance or soil fertility. In conclusion, the practice of Maize + Cowpea (1:1) intercropping combined with 75% RDN + Nano Urea (two sprays) is recommended as a sustainable and efficient strategy for improving crop quality, optimizing N utilization, and maintaining soil health in the Central Plain Zone.