Study On Nitrogen Diagnostic Method Using Active Crop Sensors Of Cotton

Nitrogen (N) is one of the most important nutrients influencing both yield and grainquality. And N supply is one of the few production factors that can be controlled and which isknown to effectively influence crop performance. Xinxiang is one of the most importantproduction bases of cotton. Xinjiang still produces and consumes more than one-thirds of theChinese cotton. The yield depends on chemical fertilizer, especially N. Unreasonablefertilization caused environmental pollution and increased costs. In order to improve thenitrogen using efficiency,real-time, rapid, nondestructive testing technique have been used toobtain the growth and nutrient status of cotton.This was did at agriculture experiment station of Shihezi University College. Theexperiment set up4N levels (N0：0kg hm-2、N1：150kg hm-2、N2：300kg hm-2、N3：450kg hm-2),4water levels(W0：160m3hm-2、W1：240m3hm-2、W2：320m3hm-2、W3:400m3hm-2).Cotton species was Xin Lu Zao45(XLZ-45).NDVI and RVI of cotton canopy have beentested by Greenseeker and obtain SPAD of the function leaves with SPAD-502. The relationbetween NDVI、RVI、SPAD and the status of nitrogen metabolism. The variety law of theseindex was studied after different water and N status. Elucidated the correlation of these indexand the optimal period for N. N diagnose model based Greenseeker and SPAD-502was built.The main results are as following:1.NDVI had significant difference between different N levels except W0, general trendof NDVI was N3>N2>N1>N0；RVI has no significant difference between different N levels,general trend of RVI was N0>N1>N2>N3. The trend of SPAD is similar to NDVI.2.At various periods,NDVI and SPAD are positive correlated with dry weightaccumulation、leaf Area Index(LAI)、leaf nitrogen content、plant nitrogen content and cottonyield. NDVI were significant or highly significant correlation with the parameters inflowering and boll stage. The correlation between NDVI and seed cotton yield was significantin the boll stage. RVI is a negative correlation between the other all growth stages and did notreach significant levels. SPAD of each growth stage were highly significant or significantpositive correlation between other parameters except LAI.3. Based on the results of correlation analysis between the various parameters,Theestablishment of various growth parameters and estimation model based on NDVI Nitrogencanopy. NDVI at flowering and boll stage can be used to fit the plant dry matter accumulation,leaf area index, leaf nitrogen content and nitrogen plant nitrogen accumulation. Thecoefficient of determination in flowering were:0.7064,0.7339,0.8258,0.7622, bloomingperiod were0.5113,0.5653,0.5189,0.6952coefficient of determination, have reached asignificant level; NDVI in boll seed cotton yield estimation model of coefficient of0.5042inthe decision significant level4. Correlation analysis between reference to the parameters, each growth parameters andestimation model based on SPAD Nitrogen canopy were be established. Prediction modelbased SPAD about dry matter accumulation of cotton to fit a quadratic function of the highest degree. In the squaring stage, flowering, blooming period and boll stage, R20.5458,0.7703,0.9048and0.7948, respectively; SPAD and leaf nitrogen content of the linear regressionequation, R2in four growth stages, respectively was0.8230、0.8292、0.7835and0.6846.SPAD yield estimation model fit in the bell of up to0.7358.5. Based field data collection at each growth stage, the results of the model were tested:Estimation model based NDVI of dry matter accumulation, LAI, leaf nitrogen content,nitrogen accumulation amount at flowering stage R2was0.6442,0.8270,0.7704and0.4903;during the blooming period was0.6374,0.6496,0.5874,0.8275, respectively; NDVI yieldestimation model fit in the bell of up to0.6650.6. R2max of dry matter estimate model based SPAD was0.6485in the bloomingperiod,leaf N R2was0.5780in squaring stage. SPAD accumulation of plant nitrogen fitnesslevels were not significant in each stage. SPAD to predict the suitability of seed cotton yieldin addition to squaring stage are very significant level, up to the bell of fitness0.7908.7. Comprehensive results of this study: NDVI and SPAD value based on spectralparameters of active remote sensing can be used for growth monitoring and nitrogen diagnosis,RVI was not competent. Best diagnostic period based on Greenseeker were flowering and bollstage, the optimal diagnosis indicators was LAI, nitrogen diagnosis based on SPAD, Leafnitrogen content of indicators is the best choice. Insufficient moisture conditions (W0) is unfitfor nitrogen nutrient diagnosis.