Red Edge Position Based Estimation Of Potato Nitrogen Nutrition

Hyperspectral remote sensing technology has a wide range of application prospects in agriculture and can be used to monitor the status of vegetation growth and study the relationship between the spectrum and physical and chemical properties of vegetation.The traditional vegetation index based on the red light band is prone to saturation,which has great influence on the diagnosis of crop nitrogen nutrition.The red edge position is considered to be a spectral parameter closely related to crop nitrogen nutrition and is often used to monitor the chlorophyll or nitrogen content of crops.Accurate calculations are very important.In this study,drip-irrigated potato was used as the research object to compare the accuracy and accuracy of the predicted red-side position of the six methods on the above-ground potato nitrogen concentration,the SPAD value of the plant,and the nitrogen uptake above the shoot。In order to determine the calculation method that is more suitable for the red edge position of the potato canopy spectrum,the red edge position was used to predict the ability to predict nitrogen nutrition and SPAD value of the potato during the key growth period of the potato.The results showed that(1)The reflectance of different varieties of potato varieties was different.The double peak phenomenon of the first derivative curve of canopy reflectance in the procreation period is gradually obvious,but there is no obvious effect on the extraction of the red edge position.(2)The red edge position has a good correlation with nitrogen concentration during the period from tuber formation to starch accumulation.In the three-year comprehensive data,the correlation at the seedling stage was negative.The determination coefficient of the regression model is 0.55,and the predicted value and observation value can reach 0.44.The prediction accuracy is higher,and the minimum of RMSE and RE is 3.96 g/kg and11.46%.(3)The correlation of SPAD value of the plants during the whole period of potato growth was good,with the highest correlation of tuber forming period.The regression model determines that the coefficient can reach 0.52.The predicted value and the observation value determine the maximum coefficient of 0.55 and the highest accuracy,and RMSE and RE can reach 3.45 and 7.01%.(4)During all the reproductive years of the potato,the red edge position only had a good correlation with the uptake of nitrogen in the plant on the ground during the seedlingstage to the tuber formation stage,and severe saturation occurred in the later stage of the birth.The determination coefficient of regression model was 0.50,and the predicted value was 0.61.The prediction accuracy was the lowest compared with nitrogen concentration and SPAD value,and RMSE and RE had better be 17.26 kg/ha and 22.65%.(5)The red edge position obtained by the linear extrapolation method has the largest amplitude change in all methods,is also the most sensitive to each prediction index,and can have a certain mitigation effect on the saturation phenomenon,and can select the optimal optimization band according to the change of the prediction index.But the calculation process is complex.In this study,the suitable calculation method of red edge position for potato canopy spectrum was found out and the optimal monitoring period for potato plants was determined,which provided the theoretical basis for rapid and accurate information of potato canopy nitrogen concentration.