Study On Construction Critical Nitrogen Concentration Dilution Models Based On Plant Organs And Diagnosis And Regulation Of Wheat In The Middle And Lower Reaches Of The Yangtze River

Nitrogen fertilizer plays an important role in wheat production,and the excess or deficit of nitrogen fertilizer will affect the growth,yield and quality of wheat.Scientific nitrogen fertilizer management,not only can improve crop yield and quality,but also improve crop nitrogen use efficiency,reduce production costs and reduce environmental pollution,resulting in a huge social,economic and ecological benefits.In this study,the dry matter weight,nitrogen concentration,leaf area index of plant shoots were carried out and tested in the key growth stages in wheat plot experiments involving multi-species and nitrogen treatment in Rugao City,Huai'an City and Sihong County,Jiangsu Province;Stem and leaf ratio,carbon and nitrogen ratio were used to analyze the changes of these growth indexes and nitrogen nutrition index.The model of wheat nitrogen concentration dilution and model parameter estimation based on different organ index were established.The nutrient status of nitrogen nutrition index(NNI),nitrogen deficit(AND,kg.ha-1),nitrogen requirement(N requirement,NR,kg.ha-1).On the basis of this,a nitrogen fertilizer regulation algorithm based on nitrogen nutrition index and nitrogen fertilizer control method based on nitrogen fertilizer optimization algorithm(NFOA)were constructed.First,the wheat nitrogen concentration model was constructed by using different nitrogen fertility experiments in different regions,varieties and years(Nc = 3.61LDM-0.19,R2 = 0.77;Nc = 2.50SDM-0.44,R2 = 0.89;Nc = 4.16PDM-0.41,R2 = 0.87;and Nc = 3.82LAI-0.36,R2 =0.81),and the critical nitrogen concentration model under each index was comprehensively compared.The NNI,AND and NR indexes of four critical nitrogen concentration models were systematically analyzed.The relationship between the critical nitrogen concentration model on SDM based and PDM-basis was the best.The NNI based on different indicators of the critical nitrogen concentration models estimate the relative production(RY),found that the NNI based on SDM will be the best to estimating RY.Furthermore,the quantitative relationship between canopy vegetation index,stem/leaf ratio and C/N ratio and model parameters were analyzed by using the model parameter estimation method to clarify the parameter variation of wheat nitrogen concentration dilution model based on different organ index.First,the variance analysis of the parameters a and b of the critical nitrogen concentration model of wheat in different years,varieties and regions showed that there was no difference between the parameters b and there was a significant difference between the parameters a.Therefore,when estimating the parameters of the nitrogen concentration model,only the parameter a value is estimated.The results show that the canopy vegetation index has the best estimation result for the parameter a at the jointing stage,and the result of the estimation of the parameter a based on the canopy vegetation index is based on the normalized vegetation index(NDVI)The estimated value of the parameter a is a = 13.527*x-4.2339,R2=0.8600;based on the ratio vegetation index(RVI):a = 0.8963*x + 0.2967,R2 = 0.8532;Ste/leaf ratio(S/L)is one of the reasons for the decrease of plant nitrogen concentration.C/N ratio also plays an important role in plant growth.Therefore,NDVI can be used to analyze stem and leaf ratio and carbon and nitrogen.The results are as follows:S/L = 0.0786e3 7658x,R2 = 0.8335,RRMSE = 0.1334;C/N = 3.8445e0.8176x,R2 = 0.7102,RRMSE = 0.1360.The estimated values of the parameter a were the best at the jointing stage.Based on the ratio of S/L to the critical nitrogen concentration of wheat plant,the parameter a was estimated to be a = 4.2113*(S/L)+0.7074,R2 = 0.8584,while based on the ratio of C/N to the critical nitrogen concentration of wheat plant,the parameter a was estimated to be a =2.5696*(C/N)-12.254,R2=0.8605.Finally,a new nitrogen fertilizer regulation method based on NFOA and NNI were established.Using the historical test data,the parameters of nitrogen fertilizer regulation model were quantified.The experimental data were used to test the model.It was found that the two methods could control the nitrogen fertilizer,and the corresponding nitrogen fertilizer treatment and nitrogen fertilizer treatment could be regulated by nitrogen fertilizer.(NAE,kg.kg-1),nitrogen use efficiency(NUE,%),nitrogen partial productivity(PFP,kg.kg-1),nitrogen fertilizer physiological efficiency(NAE,kg.kg-1)reached a high level.