Preliminary Study On The Appropriate Amount Of Nitrogen Application For Annual High Yield In Rice And Wheat

This experiment was carried out in the experimental field of Shatou Town,Guangling District,Yangzhou City,Jiangsu Province,China,between 2019 and 2021.This experiment conducted a suitable annual nitrogen application for rice and wheat by combining different fertilizer applications during rice and wheat fertility periods.In the rice experiment,two conventional japonica rice varieties,Nangeng 5055 and Nangeng 5718,were planted by machine with six nitrogen levels:0 N（0 kg/667 m2=0 kg/ha）,12 N（12 kg/667 m2=180 kg/ha）,16 N（16 kg/667 m2=240 kg/ha）,20 N（20 kg/667 m2=300kg/ha）,24N（24kg/667 m2=360kg/ha）,28N（28kg/667 m2=420kg/ha）;In the wheat experiment,only one variety,Yangmai 23,was used as the test material,and five nitrogen levels were set:0N（0kg/667m2=0kg/ha）,12N（12kg/667 m2=180kg/ha）,16 N（16kg/667 m2=240kg/ha）,20 N（20kg/667 m2=300kg/ha）,and 24 N（24kg/667 m2=360kg/ha）.Field experiments were used to investigate the effects of different nitrogen application combinations of rice and wheat on yield formation and nitrogen uptake of rice and wheat.It provided a scientific backin for applying nitrogen fertilizer to rice and wheat crops on an annual basis.Main findings of the experiments:1.With increased nitrogen application,rice yield increases at first,then decreases.The 20N nitrogen application treatment produces the highest yield of 8.62 t/ha;rice yield is influenced by the nitrogen application from the previous stubble wheat season.When the previous stubble wheat nitrogen application is 0,the rice yield increases at first,and then decreases as the nitrogen application increases.The nitrogen application in the rice season does not exceed 20N;however,the rice yield gradually increases as the nitrogen application in the previous stubble wheat season increases.When the nitrogen application in the rice season exceeds 20N,the rice yield gradually decreases with the increase of the nitrogen application in the wheat season.In the middle and early fertility stages,the spike rate of rice decreased while the number of tillers increased with increased nitrogen application,and then showed increasing and then gradually decreasing levels in the later stages.The dry matter accumulation of rice increased with increasing nitrogen application from transplanting to tasseling;during the period from tasseling to maturity,it showed a significant increase,then decreased with increasing nitrogen application,reaching a maximum under the treatment of 20N nitrogen application.Rice growth rates followed the same pattern as dry matter accumulation.2.Rice had the highest nitrogen content at the jointing stage,followed by the heading stage,and finally the maturity stage.The nitrogen uptake of rice crop transplanting,jointing,and heading increased as nitrogen application increased;however,from heading to maturity,rice nitrogen uptake increased and then decreased as nitrogen application increased;nitrogen uptake was highest under 20N treatment.Rice nitrogen utilization increased and then decreased as nitrogen application increased;physiological utilization,biased productivity,and agronomic utilization all decreased as nitrogen application increased,and the decrease was more noticeable after nitrogen application exceeded 16N treatment;the nitrogen requirement of 100 kg of rice seeds gradually increased as nitrogen application increased.3.With increasing nitrogen application,wheat yield increases first,then decreases,with the 16N treatment producing the highest yield（6.4 t/ha）.The higher the nitrogen application during the wheat period was under the 0 N and 12 N treatments,the higher the yield of the preceding crop;nitrogen application during the wheat period was before 16 N,and there was still a certain role of different nitrogen application during the rice stage;nitrogen application during the wheat period was before 16 N,and there was still a certain role of different nitrogen application during the rice stage.The yield increased slightly when nitrogen application was increased from 0 N treatments to 20 N treatments in the previous crop.The yield of wheat did not increase after nitrogen application reached 20 N in the wheat season,but it did slightly decrease with further nitrogen application in the rice stage;based on yield data,the reasonable nitrogen application in the rice and wheat annual was 32-36 kg/667 m2（480-540 kg/ha）.Wheat spike rate decreased as nitrogen application was increased.With increased nitrogen application during the wheat season,the accumulation of dry matter in wheat increased.It then decreased as nitrogen application increased in the rice season under the 0N and 12N treatments,but there was no significant change in the wheat season after the 18N treatment.4.Wheat had the highest nitrogen content at the jointing stage,followed by the heading stage,and finally the maturity stage.The nitrogen content of the whole wheat plant has increased in various periods as a result of increased nitrogen application.The nitrogen application in the rice period had some effect on the nitrogen content of wheat under the treatments of 0N and 12N application in the wheat period,and the higher the nitrogen application in the previous crop,the higher the nitrogen content of wheat;however,when wheat was under the higher nitrogen application treatment,the effect of nitrogen application in the rice period was not significant.Wheat nitrogen uptake increased as the nitrogen application level increased,but did not increase significantly once the nitrogen application level reached 16N.When nitrogen application was increased,the nitrogen uptake rate of wheat increased and then decreased,reaching its maximum under the treatment of nitrogen application of 16 N in the wheat period,after which it began to decline;nitrogen application in the rice period also affected the nitrogen uptake rate of wheat,and under the treatment of 12 N in the wheat season,the nitrogen uptake rate of wheat increased as nitrogen application was increased.Nitrogen application in the wheat season increased with increasing nitrogen application in the rice season,up to the 16 N nitrogen uptake rate of wheat.Despite this,it did not change significantly after the wheat season’s nitrogen application up to the 16 N level.During the wheat season,the agronomic utilization of wheat showed a trend of increasing and then decreasing with the nitrogen application level.The higher the nitrogen application level in the wheat season,the lower the physiological utilization and bias productivity;as the nitrogen application level in the rice season increased,the nitrogen requirement of 100 kg of wheat grains decreased,then increased.