Potassium nutrition in hybrid rice
1987
Fan Mingxieng | Ge Dangzhi | Jiang Longyin (Hunan Agricultural Coll. (China))
Hybrid rice Vu 35 was studied at different K levels on a Quaternary red clay soil with pH 6.0, 2.76% organic matter, 70 ppm available K, 240 ppm slowly available K, and 0.188% N. Conventional variety Xiang 9 was the check. KCl was applied at 0, 110, 220, and 40 kg/ha in main plots with 350 kg urea and 550 kg superphosphate/ha. All the P, 2/3 N, and 1/3 K were applied before transplanting, 1/3 N and 2/3 K at tillering. The 2 varieties were transplanted in 4- x 8-m subplots with 3 replications. Samples were taken at transplanting, tillering, panicle initiation, full heading, and maturity for soil, plant, and yield analyses. K content increased with increased K fertilizer at all stages for both varieties; however, Vu 35 was more sensitive to K supplied from panicle initiation to heading and needed more K. The leaf area index was significantly correlated with plant N content (r = 0.91) at early growth stages and with plant K content (r = 0.94) at late growth stages. Total photosynthetic area and net assimilation rate had increased significantly at heading and maturing stages, which led to 13-44% increase in dry matter production with K application. Grain yield of Vu 35 increased 3-8% with K level, but increase/kg K2O applied declined resulting in lower K economic efficiency at higher K levels. Yield of Xiang 9 was significantly lower than that of Vu 35 and did not show obvious response to K fertilization.
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