Effects Of Nitrogen Application Rate And Sowing Density On Growth And Yield For Mechanical Direct Seeding Rice

For the sake research of suitable nitrogen application rate and sowing density of mechanical direct seeding rice in Jianghan Plain,Hubei Province,three rice varieties(C Liangyou Huazhan,Fengliangyou 4 and Huanghuazhan)were used as experimental materials from 2018 to 2019.The split zone test design was carried out,we designed three nitrogen application levels as the main area.:240 kg/hm~2 (N240),195 kg/hm~2(N195)and 150 kg/hm~2(N150),and no nitrogen fertilizer(N0)as control.In the experiment.The three planting densities were subregion:25 cm×14 cm(D14),25 cm×16 cm(D16)and 25 cm×18 cm(D18).In this experiment,the effects of nitrogen application rate and sowing density on population growth,lodging resistance and yield of mechanical direct seeding rice were studied.The results show that:1. The yield of different rice varieties was different:C Liangyouhuazhan>Fengliangyou 4>Huang Huazhan.The application of nitrogen fertilizer could significantly increase the yield of rice,but there were differences among different varieties.The yield of C Liangyou Huazhan and Fengliangyou 4 increased at first and then decreased with the increase of nitrogen application.For Huang Huazhan,there was no significant difference in yield between treatment N195 and treatment N150,but the yield of treatment N240 increased significantly.The effects of sowing density on the yield of different varieties were different:the yield of C Liangyou Huazhan and Fengliangyou 4 increased at first and then decreased with the increase of sowing density,and the yield of Huang Huazhan was proportional to the sowing density.Under the interaction of fertilizer and density,the yield of C Liangyou Huazhan,Fengliangyou 4 and Huang Huazhan was the highest under treatment N195D16,N195D16 and N240D14/N240D16,respectively.2. The application of nitrogen fertilizer increased the panicles and grains per panicle,but decreased the seed setting rate.Reducing the sowing density slightly increased the grains per panicle and seed setting rate of rice,but the effect of sowing density on the effective panicle of Huang Huazhan was not significant.3. The tillers,dry matter accumulation and light energy interception rate of direct seeding rice showed a parabola trend under different nitrogen application rates.The SPAD value and LAI of rice were the highest in treatment N240/N195,but there was no significant difference among different sowing densities.4. The application of nitrogen fertilizer increased the center of gravity height,Internode length,lodging coefficient and stem plumpness of rice,which was not conducive to lodging resistance of rice.Low sowing density is beneficial to the ontogeny of rice,thus enhancing the lodging resistance.5. The brown rice rate,milled rice rate,head rice rate and protein content increased with the increase of nitrogen application rate,at the same time,the chalky grain rate and chalkiness degree of rice also increased,and the amylose content of rice was inversely proportional to the nitrogen application rate.Reducing the sowing density slightly improved the rice quality.To sum up,under the condition of machine direct seeding,for C Liangyou Huazhan and Fengliangyou 4,the sowing density of nitrogen application 195kg/hm2combined with 25cm*16cm was suitable in this region,while for conventional rice variety Huang Huazhan,nitrogen application rate 240kg/hm2 combined with sowing density 25cm*14cm and 25cm*16cm was suitable.According to the different varieties and planting requirements of direct seeding rice,the cultivation measures of low nitrogen application rate combined with high sowing density and high nitrogen application rate with low sowing density are also worth popularizing.