Evaluating Multi-split Topdressing as an Option for Improving Nitrogen Management in Lowland Rice

摘要

Background and Objective: The contribution of nitrogen fertilizer to grain yield of irrigated rice is phenomenal in Ghana. However; the expected yield level based on the crop potential in this cultivation system is yet to be realized, despite the systematic increase in nitrogen fertilizer rate of application. This could be mainly attributed to inappropriate timing of fertilizer application. Fertilizer management strategy is therefore needed to ensure effective utilization by the rice crop for improved yield. Materials and Methods: The field experiment was conducted at the University of Ghana?s Soil and Irrigation Research Centre-Kpong during 2014 and 2015 cropping seasons to evaluate the influence of N fertilizer rates and timing of application on rice yield. A 3×2 factorial experiment was laid out in a randomized complete block design and replicated three times. Fertilizer rate and time of nitrogen application were the factors involved. The levels of fertilizer rate were: 0, 75, 90 and 120 kg N ha^?1, while time of the nitrogen application included; conventional practice (2 times, basal and top dress) and multi-split (weekly application till booting stage) and determined using two-way analysis of variance (ANOVA) using GenStat statistical software (12th edition). Results: High N fertilization rates increased growth and yield components , grain yield . However, better grain yield was obtained when N was multi-split for topdressing (eg. 90 kg N; 5.0 t ha^?1) than the conventional method (90 kg N; 4.6 t ha^?1). Conclusion: The study revealed that, the generally followed blanket nitrogen application rate and two-split traditional practice, was not adequate to obtain higher yields. Rice response to fertilizer was better at 120 kg N ha^?1 than the other lower N rates. However, 120 kg N ha^?1 applied at seven splits performed better (5.4 t ha^?1) than 120 kg ha^?1 applied at the conventional (5.0 t ha^?1) application of basal and top-dress at panicle initiation stage.