The Hyperspectral Monitoring Of Grain Dry Matter And Nitrogen Dynamic Accumulation In Winter Wheat

Winter wheat is the third largest food crop in China after rice and corn.This study used hyperspectral remote sensing technology to realize the real time and accurate monitoring of carbon and nitrogen accumulation during grain filling stage of winter wheat after anthesis,and provided an effective technical approach for wheat field management after flowering and prediction of yield and quality.In this study,two years nitrogen research experiments were carried out.The dynamic changes of canopy spectral characteristics of winter wheat,plant and leaf nitrogen accumulation,soluble sugar content and dry matter accumulation,grain nitrogen accumulation,dry matter accumulation and accumulation rate after anthesis under different nitrogen modes were studied.Furthermore,the spectral sensitive bands of winter wheat agronomic parameters were extracted using PLS and SMLR methods,and the corresponding spectral monitoring model were established.Combining with the establishment of research approach of "Canopy Spectral-Agronomic parameters-Grain carbon and nitrogen accumulation" and the dynamic monitoring model of grain carbon and nitrogen accumulation of winter wheat.The following conclusions were drew:(1)With the development of the reproductive period after florescence,the canopy spectral reflectance of winter wheat increased in the visible region and decreased in the near infrared region.The canopy reflectance of different nitrogen treatments were varied.With the increase of nitrogen application amount,the reflectivity increased in the visible bands and decreased in the near infrared bands.Under different nitrogen application conditions,the red edge position difference is not obvious,the red edge area and the red edge amplitude increased firstly and then decreased with the increase of nitrogen application rate.And with the advance of grouting process,the area of the red edge,the amplitude of the red edge and the position of the red edge are gradually decreasing.(2)With the development of the reproductive period after florescence,the leaf dry matter accumulation decreased and the plant dry matter accumulation increased firstly and then decreased,but the grain dry matter accumulation increased gradually.Under different nitrogen application conditions,the leaf and plant dry matter accumulation increased continuously while the grain dry matter accumulation increased firstly and then decreased with the increase of nitrogen application amount.The monitoring model of plant and leaf dry matter accumulation had high accuracy based on PLS-SMLR,and there was a good correlation and quantitative relationship between grain dry matter accumulation with plant and leaf dry matter accumulation.There were high precision(R2)and lower RMSE for the dynamic monitoring model of using grain dry matter accumulation as intermediate parameters.Finally,the model with leaf dry matter accumulation as the intermediate parameter performed best.(3)With the advance of grouting process,the plant and leaf soluble sugar content and grain dry matter accumulation rate change trend was consistent and increased firstly and then decreased.But with the increase of nitrogen application,the trend is different.The plant and leaf soluble sugar content increased gradually,while the grain dry matter accumulation rate increased firstly and then decreased.The model of leaf and plant soluble sugar content established with PLS-SMLR had high accuracy,There was a good correlation and quantitative relationship between grain dry matter accumulation rate accumulation with leaf and plant soluble sugar content.The model using soluble sugar as the intermediate parameter had the best performance,and the accuracy was obviously higher than the model established directly with PLS-SMLR.The model using leaf soluble sugar content as the intermediate variable performed worst.(4)With the advance of grouting process,The variation trend of winter wheat plants and leaf nitrogen accumulation were all decreasing.However,the trend of grain nitrogen accumulation was gradually increasing.With the increase of nitrogen application,the plant and leaf nitrogen accumulation increased gradually while the grain nitrogen accumulation increased firstly and then decreased.The monitoring model of plant and leaf nitrogen accumulation based on PLS-SMLR were all good.The correlation and quantitative relationship between grain nitrogen accumulation with plant and leaf nitrogen accumulation were also fine.Thus,For all spectral monitoring model,the model using the leaf nitrogen accumulation as the intermediate variables performed best.