Potato Nitrogen Nutrition Diagnosis Based On Green Seeker And Nitrogen Nutrition Index

Nitrogen is one of the key factors determining potato yield and quality,and unreasonable nitrogen fertilizer application leads to the reduction of fertilizer utilization rate,yield and quality decline,and increase of environmental pollution risk in potato production,so reasonable nitrogen fertilizer nutrient management is imperative.To achieve these goals,accurate nitrogen nutrition diagnosis is a prerequisite.The nitrogen nutrition index based diagnosis method is one of the means to accurately reflect the nitrogen nutrition status of crops,and the diagnostic accuracy is high,but there are shortcomings such as large sampling volume,cumbersome operation and poor real-time performance,the use of remote sensing technology for nitrogen diagnosis makes up for the shortcomings of the above methods,but factors such as crop varieties,growth period and field management are prone to diagnostic errors.The combination of remote sensing and nitrogen nutrition index（NNI）has been successfully applied to the diagnosis of nitrogen nutrition in a variety of crops,but it has rarely been reported in potatoes.In order to obtain a more accurate diagnosis scheme of potato nitrogen fertilizer,this experiment explored the feasibility of using active crop sensors to estimate potato NNI by setting different nitrogen fertilizer supplies,using Green Seeker to determine the spectral index NDVI value and RVI value,screening the optimal estimation scheme,and establishing a potato nitrogen nutrition diagnosis model based on Green Seeker and nitrogen nutrition index.The main results are as follows:（1）NDVI,TNDVI and TRVI are highly correlated with potato nitrogen nutrient index,so it is feasible to non-destructively estimate potato NNI using active crop sensors.（2）Compared with the direct method and indirect method,based on spectral index substitution method,the RMSE and NRMSE values were smaller in different ways,which was the best nitrogen nutrition diagnostic method.（3）A critical nitrogen dilution curve model based on TNDVI and RVI values was constructed:Nc=0.0593RVI^-0.372,R²=0.78.The model can overcome the influence of year and variety.In this thesis,a nitrogen nutrition index model based on spectral index is constructed:NNI_VI=TNDVI/Nc _TNDVI,this model was used to diagnose the nitrogen nutrition status of potato plants during the tuber formation stage^starch accumulation stage,and was not applicable at the seedling stage.