Study On Variable-Rate Fertilization Algorithm And Mechanism By Hyperspectral Remote Sensing Technology

The experiment was carried out on the National Precision Agricultural ResearchBasement of Xiao Tanshang , Beijing from 2003 to 2005. This dissertation mainly studiedthe variable rate technology(VRT)through extracting the winter wheat(Triticum aestivumL.) spectrum information from the hyperspectral data and SPAD readings by ASD Fro2500spectroradiometers and SPAD meter(Chlorophyll Meter),puts great emphasis on the studyof canopy N dynamic distributing character and analyzed the fertilizer mechanism ofvariable rate technology based on hyperspectral data,and the timely obtained informationof wheat growth status, especially N status, will help us to apply fertilizer and irrigationmanagement. The study constituted the variable rate diagnostic model based on differentremote sensing data,and discussed the influence of winter wheat grain yield,quality andeconomical and environmental benefits,at last,compared with the advantage anddisadvantage of different fertilizer pattern,educed the optimum variable rate model fittingBeijing agricultural producing conditions based on hyperspectral data anddifferent-position leaf SPAD readings. The results are summarized as below: 1. Variable-Rate Nitrogen Fertilization Based on Remote Sensing Data:The Nfertilization optimization algorithm(NFOA) was developed to determine the needed N rateper 1 hm2 based on predicted yield and specific OSAVI per plot, The NFOA accounts forspatially variable potential yield, early stubble N uptake, and responsiveness of the crop toN input. This study demonstrated that crop reflectance measurements using optical sensorscan be used to set more efficient and profitable fertilization levels. The technologyincreased significantly grain yield and dry matter of the winter wheat,and decreased thevariable coefficients of grain yield and dry matter. The NO3-N concentration decreasedcompared with CK treatment in 20cm to 40cm soil,and improved the nitrogen useefficiency evidently. Variable-rate fertilization reduced soil nitrate concentration,andrestrict the potential of underground water pollution. But the grain quality retained thesame level as CK plots(balance N rates) and C plots(uniform N rates),and increasedthe spatial variety. 2. Variable-Rate Nitrogen technology Based on different site leaf SPAD readings:Thetest studied the VRT using normalized difference SPAD(NDSPAD) value for the firsttime,analyzed the influence of grain field ,grain quality,canopy spectrum anddifferent-position leaf SPAD readings. The research indicated that the ratio of inverse oneand inverse two could be used to estimate the N nutrient status,and A very high correlationhas been found between hand-held chlorophyll meter readings and N concentrations inplant tissue,it can be used to predict the total N absorbed. Compared with the CK plots andC plots,the grain yield and dry matter yield improved by VRT, and can increased 500yuan/hm2, the NO3-N concentration decreased obviously,and restrained the undergroundwater pollution. The protein content increased hardly,on the contrary,the VRT increasedthe spatial variety. 3. Variable-Rate Nitrogen technology Based on soil nutrient data:The technologyincreased significantly grain yield and dry matter of winter wheat,and decreased thevariable coefficients of grain yield and dry matter. The maximum yield and minimum yieldpresented to uniform rate plots and balance rate plots. The value/cost ratio, 6.56, was thehighest among three treatments; the variable rate treatment improved the grain yield output,cost proportion, and increased the economic benefits. 4. Variable rate technology models based on canopy spectrum and SPAD readings onwinter wheat: Set up the N fertilization optimization algorithm (NFOA) based on OSAVIvalue and SPAD readings in Beijing agricultural production conditions. It provided atechno-support for precision agriculture variable rate technology. 5. Selecting the N fertilization optimization algorithm: The results of three VRTshowed that the economic benefit of VRT based on SPAD readings is the best among threeVRT, the paper suggested tha...