Growth, Yield and Agronomic Efficiency of Maize (Zea mays L.) under Different Nitrogen Rates in Western Viti Levu, Fiji

Abstract

Background: Nitrogen deficiency has become one of the major constraints limiting maize productivity in Fiji due to continuous cropping and poor fertilizer application. However, information on optimum nitrogen requirements for maize production under Fiji’s agro-climatic conditions is still limited. Methods: A field experiment was conducted at the Sugar Research Institute of Fiji, Ba, from November 2025 to February 2026, to evaluate the effects of different nitrogen rates on maize growth, yield and agronomic efficiency. The experiment consisted of a randomized complete block design with five nitrogen rates (0, 50, 100, 150 and 200 kg N ha-1) in four replications. Growth attributes, SPAD values, yield components, grain yield, biomass, harvest index and agronomic efficiency were measured and subjected to analysis of variance and regression analysis. Result: Nitrogen application significantly (p less than 0.05) improved plant height, leaf number, leaf area index, SPAD values, biomass production and yield attributes compared with the control. Treatment 200 kg N ha-1 recorded the highest grain yield (6.88 t ha-1), total biomass (19.46 t ha-1), harvest index (0.35) and grains per cob (327). Agronomic efficiency was highest at 50 kg N ha-1 (36.8 kg grain kg-1 N) and declined with increasing nitrogen rates. A strong positive relationship (R2 = 0.998) between grain yield and nitrogen application was recorded and no yield plateau was reached up to 200 kg N ha-1. The results show that maize has a high nitrogen demand in Western Viti Levu and more studies are needed to determine the optimum nitrogen requirement for sustainable production in Fiji.