Effects of Reducing and Postponing Nitrogen Application on Population Quality and Grain Yield of japonica Rice Under Paddy-upland Crop Rotations in Yunnan Plateau |
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| Authors: | XIA Qiongmei HU Jiaquan DONG Linbo QIAN Wenjuan HE Yongfu LI Guiyong LONG Ruiping ZHU Haiping YANG Congdang |
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| Institution: | 1. Institute of Food Crops, Yunnan Academy of Agricultural Sciences, Kunming 650205, China;2. Qiling District Agricultural Technology Extension Center, Qujing 655000, China;3. Yuezhou Township Integrated Agricultural Station, Qujing 655000, China; |
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| Abstract: | 【Objective】The objective is to study the effect of reducing and postponing nitrogen application from earlier stage to later stage on population quality and yield, and to improve the nitrogen utilization efficiency for japonica rice on paddy-upland crop rotation in Yunnan Province.【Method】With two conventional japonica rice varieties(Huijing 17 and Chujing 28) as materials, a field plot experiment was carried out at six nitrogen application levels (270 kg/hm2, 243 kg/hm2, 216 kg/hm2, 189 kg/hm2 and 162 kg/hm2 with the corresponding basal, tillering, spikelet-promoting and spikelet-sustaining nitrogen ratios of 5:5:0:0, 3:3:2:2, 2.5:2.5:2.5:2.5, 0:2:5:3, 0:0:6:4, 0:0:0:0).【Result】The yield, over 8 t/hm2 at zero nitrogen fertilizer level in 2016 and 2017, increased significantly with rising nitrogen application level. As compared with conventional fertilization treatment (270 kg/hm2 and 5:5:0:0), with the increasing ratio of spikelet-promoting fertilizer while reduced total nitrogen application rate, an increasing trend was observed in yield and nitrogen agronomic efficiency. The optimum treatment was a reduction of 40% in nitrogen application rate. With the reduction of nitrogen application rate, the yield increased by more than 20% and the nitrogen agronomic efficiency increased from less than 10 kg/kg to more than 20 kg/kg. After reducing and postponing nitrogen application from earlier stage to later stage, the period of young panicle differentiation was prolonged. With longer functional leaves, the ordinal number of leaf length from the top of 2-3-1-4, the efficient leaf area ratio more than 80%, and appropriate leaf area index at full heading stage, the high photosynthetic efficient population formed, which promoted the differentiation of spikelets. At the same time, the panicle-bearing tiller percentage increased, with a higher population growth rate and dry matter accumulation after heading. 【Conclusion】Optimizing the nitrogen fertilizer management can effectively reduce the application amount of nitrogen fertilizer in paddy field and improve grain yield and the utilization rate of nitrogen fertilizer of japonica rice in Yunnan. Among them, spikelet-promoting nitrogen fertilizer application with zero basal-tiller fertilizer in the rice growing season required the least input but generated the most output. |
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| Keywords: | japonica rice reduce and postpone nitrogen application to later stage grain yield population quality |
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