Canopy Spectral And Yield Monitoring Of Winter Wheat Under Combined Application Of Nitrogen And Phosphorus

Winter wheat is an important grain crop in China.Accurate monitoring of winter wheat yield is of great significance to national security and people's livelihood.Hyperspectral remote sensing technology is widely used in different crop yield estimation because of its real-time,fast,large-scale characteristics.Early monitoring of winter wheat yield can timely guide the management of water and fertilizer during crop growth period,and has a certain practical significance for increasing winter wheat yield.In order to explore the response law of canopy spectrum of Winter Wheat under combined application of nitrogen and phosphorus,clarify the changing law of spike number,grain number per spike,1000-grain weight and yield of winter wheat,and realize rapid yield estimation under combined application of nitrogen and phosphorus as soon as possible,the data of canopy spectrum,spike number,grain number per spike,1000-grain weight and yield of Winter Wheat under combined application of nitrogen and phosphorus were collected.By analyzing the correlation between canopy spectrum and winter wheat yield at different growth stages,the response of spectral reflectance to different treatments was studied.Using partial least squares regression to establish a monitoring model of yield three factors and yield,the results show that:(1)The spectral reflectance of winter wheat at different growth stages is obviously different.The canopy spectra of winter wheat at jointing stage,booting stage,flowering stage and early filling stage have the spectral characteristics of green vegetation.Winter wheat at late filling stage and mature stage do not have such characteristics because of yellowing and shedding of leaves.The reflectance trend of canopy spectra was the same under different treatments,mainly in visible and near infrared bands.(2)The spike number,grain number per spike,1000 grain weight and yield of winter wheat were different under different nitrogen and phosphorus treatments.With the same amount of phosphorus application,the higher the amount of nitrogen application,the greater the number of panicles,the grain number per panicle,1000-grain weight and yield were increased first and then decreased.With the same amount of nitrogen,the higher the amount of phosphorus applied,the number of ears and grains per ear increased first and then decreased,the 1000-grain weight decreased,and the yield increased.(3)The correlation between canopy spectrum and spike number,grain number per spike,1000-grain weight and yield of Winter Wheat under combined application of nitrogen and phosphorus was higher and showed certain regularity.From the band point of view,the correlation between 400 nm and 1349 nm is more regular,and the correlation between 1449 nm and 1800 nm and 1942 nm-2450 nm is more disorderly.From the growth stage,the overall correlation of jointing stage,booting stage,flowering stage and early filling stage is higher,but the overall correlation of late filling and mature stage is lower.(4)Using partial least squares regression(PLSR)to establish a three-factor and yield monitoring model for winter wheat yield at different growth stages.The canopy spectrum monitoring yields at different growth stages have different effects on the three factors and yield models.The better performance period is mainly grouting.In the early stage,the best monitoring period of panicle number was early filling(RC2=0.76,RMSEC=73.67,RV2=0.71,RMSEV=78.66);the best monitoring period of kernel number was early filling(RC2=0.80,RMSEC=5.34,RV2=0.75,RMSEV=5.77);the best monitoring period for 1000-grain weight is early filling(RC2=0.74,RMSEC=3.64,RV2=0.70,RMSEV=3.87);the best monitoring period for yield is early filling(RC2=0.78,RMSEC = 980,RV2 = 0.71,RMSEV = 997).