Agronomic performance of maize of contrasting maturities at varying rates of nitrogen fertilizer application in a tropical rainforest agroecology

Abstract

The agronomic response of maize (Zea mays L.) to nitrogen (N) fertilizer depends on the cultivation conditions. However, there is a knowledge gap on the optimal rates of N fertilizer application for cultivars with different days to maturities in the tropical rainforest agroecology. Field trials were conducted at the Teaching and Research Farm, University of Benin, Benin City, which lies in the tropical rainforest of Nigeria in 2019 and 2020, to evaluate the agronomic performance of maize of contrasting maturities at varying rates of nitrogen fertilizer application. The experiment was arranged in a split-plot fitted into a randomized complete block design having three replications. The main plot treatment was N rate (0, 30, 60, 90 and 120 kg N ha^–1) and sub plot treatment was maize variety (extra-early maturing (TZEE-Y POP STR C4); early maturing (2008 DTMA-Y STR); intermediate maturing (BR. 9928 DWRSR) and late maturing (TZL COMP.4 C4). Results showed non-significant N rate × variety interactions for measured traits except 1000-seed weight. However, optimum grain yield was achieved at 60 kg N ha^–1 beyond which rate, additional N did not cause any significant increase, suggesting that application of N above this optimum rate to maize plants may result in fertilizer wastage. The intermediate and late maturing varieties out-yielded the extra-early and early maturing varieties, indicating better utilization of available N. Therefore, in the rainforest agro-ecology, intermediate and late maturing maize varieties should be grown at 60 kg N ha^–1 for optimum yield.