Effects Of Nitrogen Application Rate And Planting Density On Growth And Development Of Wheat And Rice

Optimal nitrogen(N)fertilizer application and suitable cultivation density are important measures to obtain high grain yield.N fertilization and planting density can increase crop per unit yield to a certain degree.However,excessive N application will restrict yield formation and bring a series of environmental pollution.Therefore,the effects of different nitrogen dosage and densities on the growth and development of wheat and rice were studied in this paper.Meanwhile,we also compared the growth response of conventional rice and hybrid rice to different N application rates and planting densities,which could provide a theoretical basis and guidance for actual production.From 2015 to 2016,the experiment was carried out in the long-term positioning experimental field of the Agricultural Scientific Research Institute of Rugao City,Jiangsu province.In the wheat experiment,there were two main factors of wheat planting density and nitrogen fertilizer use.The test was divided into 5 nitrogen gradients:0,50,100,200 and 300 kg hm-2,which were recorded as N0,N50,N100,N200 and N300,respectively.Two density level were settled:high density(HD)with planting spacing of 22 cm and low density(LD)with planting spacing of 28 cm.However,The experiment of rice mainly includes three factors:planting density,nitrogen dosage and variety.Five N levels were settled in the rice experiment with 0,90,180,270,and 360,which were recorded as N0,N90,N180,N270 and N360,respectively.Two density levels were settled:high density(HD)with 35.71 ×104 holes per hectare;while low density(LD)with 23.81 ×104 holes per hectare.Conventional rice "Zhendao 11" and Hybrid rice "Liangyou 3218".The main conclusions of this article are as follows:1.Increasing the application rate of nitrogen fertilizer,the cumulative amount of dry matter in the ground of wheat and rice has gradually increased,which was higher under HD than that under LD.At the same time,dry matter accumulation of hybrid rice was higher than that of conventional rice.Meanwhile,the single-hole biomass of rice under LD is higher than that of HD,which indicate LD condition was benefit for growth and development of individual plant,while HD condition showed a certain advantage in population.However,The maximum number of tillers in each hole of hybrid rice is larger than that of conventional rice,but the hybrid rice has lower spike rate than conventional rice.Our results showed that,the average ear formation rate in conventional rice was 0,89,which was 0.72 in hybrid rice.2.With the increase of nitrogen fertilizer application,the yield of wheat and rice showed the trend of increasing first and then decreasing.In the experimental results,the optimum fertilization amount of wheat yield was estimated to be about 200 kg hm-2 with the maximum yield of 6183 kg hm-2,and the optimal yield of conventional rice was 150 kg hm-2 and low density planting conditions,and the optimal nitrogen rate was 90 kg hm-2 and low density planting conditions for hybrid rice,and nitrogen fertilizer to conventional rice.The increase of yield is greater than that of hybrid rice.The grain number of hybrid rice is significantly higher than that of conventional rice,which is the main reason for the yield of hybrid rice higher than that of conventional rice.3.N application levels and planting densities significantly affected the N accumulation and utilization in rice.With the increase of nitrogen fertilizer input,the N accumulation in shoots gradually increased in rice plants under HD,which was higher than that of LD.The hybrid rice was higher than conventional rice.For conventional rice,the YCN was:32.99%(LD),27.97%(HD).The hybrid rice was 22.53%(LD)and 11.55%(HD)was significantly lower than conventional rice.Moreover,Ycn is significantly greater than HD under LD conditions.There was no significant difference between nitrogen agronomy efficiency and nitrogen partial productivity LD and HD,and there was a negative correlation between nitrogen application rate and nitrogen application rate.conventional rice PEN was significantly higher than hybrid rice.In conclusion,the optimum nitrogen application rate for wheat in this study is 200 kg hm-2,and conventional rice and hybrid rice are 150 kg hm-2 and 90 kg hm-2 respectively.The main reason for the higher yield of hybrid rice than conventional rice is that it has larger panicle type and more grains per spike.The characteristics of fertilizer requirement of conventional rice and hybrid rice are different.