Responses of upland NERICA rice varieties to nitrogen and plant density

Improved varieties, nitrogen fertilizer, and plant spacing have been identified for increasing upland rice productivity. However, these factors have not been adequately investigated on interspecific rice, New Rice for Africa (NERICA1). Different levels of nitrogen (0, 30, 60 and 120 kg ha71) and plant spacing (dibbling: 30 6 30 cm, 20 6 20 cm, and drilling: 25 6 5 cm) on the growth and yield of three interspecific rice varieties and a check variety were evaluated on Terre de barre soils. Rainfall in both years was unevenly distribution which caused drought in both years. Across both years, rice yield was significantly depressed with 60N and 120N by 53–81%, compared with other N levels. NERICA4 with 30N gave the highest panicles density and harvest index, and the best yield (1.2Mg ha71). Wide spacing of 20 6 20 cm or 30 6 30 cm with four plants stand71 was optimum for the NERICA. Drilling rice at 25 6 5 cm with one plant stand71 depressed yield. Results showed that in smallholder upland ecosystems prone to unpredictable drought, wide spacing and low N can be recommended for production of NERICA.

现有研究已明确可提升旱稻生产力的改良品种、氮肥施用量及种植行距，但针对非洲新稻（New Rice for Africa, NERICA1）这一种间杂交水稻，上述因素的相关研究仍不够充分。本研究在黏红壤（Terre de barre soils）上开展田间试验，设置梯度氮肥水平（0、30、60和120 kg·ha⁻¹）与种植行距配置（点播模式：30×30 cm、20×20 cm；条播模式：25×5 cm），共评估3个种间杂交水稻品种及1个对照品种的生长与产量表现。试验两年间降雨分布均不均衡，引发了干旱胁迫。综合两年的试验数据来看，与其他氮肥水平相比，施用60 kg·ha⁻¹和120 kg·ha⁻¹氮肥会使水稻产量显著降低53%~81%。施用30 kg·ha⁻¹氮肥的NERICA4表现最优，其穗密度、收获指数均达峰值，产量亦为最高（1.2 Mg·ha⁻¹）。对于NERICA品种而言，每穴留苗4株、采用20×20 cm或30×30 cm的宽行距种植为最优方案；而采用25×5 cm条播且每穴留苗1株的处理则会显著降低产量。研究结果表明，在易遭遇不可预测干旱的小农旱作生态系统中，可推荐采用宽行距种植与低氮肥施用量的方案开展NERICA水稻生产。