Effects of Nitrogen Management Practices on Nutrient Use Efficiency, Growth, and Biomass Production of Lowland Rice (Oryza sativa L.)

Rice (Oryza sativa L.) productivity is often constrained by low nitrogen use efficiency (NUE), leading to reduced yields and increased environmental nitrogen losses. This study evaluated the effects of different nitrogen management practices on the growth, yield, biomass accumulation, and NUE of lowland rice under screen house conditions at the Federal University of Agriculture, Abeokuta, Nigeria. The experiment was arranged in a Completely Randomized Design (CRD) with seven nitrogen treatments: control, conventional split application, phenology-based split application, slow-release nitrogen, green manure + reduced nitrogen, foliar nano-urea, and poultry manure + reduced nitrogen, each replicated three times. Nitrogen management practices did not significantly affect plant height during the early growth stages but showed significant differences at 14 weeks after transplanting (WAT), where conventional split application (197.1 cm) and slow-release nitrogen (196.1 cm) produced the tallest plants compared with the control (153.1 cm). Tiller production differed significantly at 8–12 WAT, with poultry manure + reduced nitrogen producing the highest number of tillers. Yield components, including panicle length, grains per panicle, 1000-grain weight, and grain yield per plant, were not significantly affected (p ≥ 0.05), although conventional split application recorded the highest numerical grain yield. Partial factor productivity was significantly improved by phenology-based split application (23.83) and conventional split application (21.83). Poultry manure + reduced nitrogen also produced the highest whole-plant wet (381.7 g) and dry (134.77 g) biomass. These findings indicate that split nitrogen application and integrated organic–inorganic nitrogen management can improve NUE and biomass production, contributing to more sustainable lowland rice production.