Effect Of Low Nitrogen Rate Combined With High Plant Density On Grain Yield And Nitrogen Use Efficiency In Machine-transplanted Double Rice

Under the field experiment condition,asking hybrid rice plant Zhuliangyou 819 and conventional rice Zhongjiazao 17 as the early rice materials,and hybrid rice Taiyou 390 and conventional rice Xiangwanxian 13 as the late rice materials with four nitrogen and density levels in liuyang and hengyang.Zero-N and conventional density(0 kg N /ha,285700 holes / ha),zero-N and high density(0 kg N /ha,363600 holes / ha),low N rate and high density(120 kg N /ha,363000 holes / ha)and conventional N rate and density(150 kg N /ha,285700 holes / ha)were set up using split panel design.The tiller dynamics,dry matter content,leaf area index,yield and its components,chlorophyll relative content(SPAD value)and nitrogen use efficiency were calculated.The results were as follows:1.Under low nitrogen tight conditions,there is no significant difference in the yield of double-season rice compared with conventional cultivation.2.Under the condition of low nitrogen close planting,the nitrogen fertilizer partial productivity of Liuyang early rice hybrids,conventional varieties,late rice hybrids,conventional varieties,Hengyang early rice hybrids,conventional varieties,late rice hybrids and conventional varieties increased by 30.9%,26.7%,21.6,respectively.%,21.5%,10.2%,14.7%,23.5% and 28.5%.Nitrogen use efficiency increased by 21.4% and 8.2%,21.9% and 17.8%,2.4% and 3.2%,16.6% and 6.5%,respectively.The fertilizer utilization rate of double-season rice transplanted under low nitrogen close planting conditions was significantly improved.3.Under low nitrogen tight conditions,the dry matter accumulation of the machine inserted in late rice is significantly higher than that of conventional cultivation,the cumulative amount of dry matter in the early rice was not significantly improved compared with conventional cultivation.4.Under low nitrogen tight conditions,the nitrogen accumulation in the shoots of late rice was significantly higher than that of conventional cultivation,the accumulation of dry matter in the shoots of early rice was not significantly different from conventional cultivation.5.Under low nitrogen tight conditions,significantly improved tillering dynamics of double-season rice,leaf area index and chlorophyll relative content did not change significantly.6.Comprehensively speaking,Low-nitrogen close planting can effectively improve nitrogen use efficiency while ensuring relatively stable yield,is a relatively good rice planting mode.