Growth Indicator Monitoring Study Based On Maize Canopy Spectral NDVI

The size of the normalized vegetation index is a better indicator of the crop's growth.When a crop is subjected to water or nutrient stress,it causes changes in leaf area index,biomass,chlorophyll content and cover and thus have an impact on NDVI of the crop population.Above-ground biomass,leaf area index(LAI)and chlorophyll content(SPAD)are important agronomic indicators of crop growth.parameters,and there is a close relationship between the three.Accurate estimation of these growth indicators is important for crop growth monitoring,yield estimation,nitrogen nutrition diagnosis and field management.Translated with www.DeepL.com/Translator(free version)The experiments were conducted in 2019 at Tongzhou Experimental Base,Beijing Academy of Agricultural and Forestry Sciences(Experiment 1)and Gongzhuling Experimental Station,Institute of Crop Science,Chinese Academy of Agricultural Sciences(Experiment 2),respectively,and the test materials were Xianyu 335(XY335)and Zheng dan 958(ZD958),and the plots were designed as randomized zone groups.Experiment 1 was used to analyze the developmental status of maize growth and yield formation in response to nitrogen application,and Experiment 2 was used to construct a monitoring model of maize growth indicators based on canopy spectroscopy.By obtaining canopy spectral data and ground agronomic parameters for different treatments,the dynamic characterization of canopy spectral characteristics of maize under different treatments in spring was clarified,and a monitoring and diagnostic model of maize leaf area index,above-ground biomass and nitrogen nutrient status was established to provide technical support for timely,rapid and non-destructive acquisition of maize growth status and nitrogen nutrient status.The main findings of this study are as follows.1.The dynamic variation of LAI between the two species under different nitrogen treatments showed an increasing and decreasing trend,reaching its maximum at the spike stage.Nitrogen treatment significantly increased the proportion of dry matter accumulation after maize spit,and N5 treatment increased the proportion of dry matter accumulation in ZD958 and XY335 by 10.1%and 14.3%,respectively.The contribution of dry matter to the dry matter of the seeds was 0?20.2%after spitting,while the N1 treatment of the XY335 variety contributed the most,up to 20.2%,and there was no significant difference between the nitrogen treatments of ZD958.Nitrogen fertilizer utilization was not different between the fertilizer treatments,and the intermediate productivity and agronomic efficiency of the two products were significantly different between the nitrogen treatments.2.The dynamics of NDVI change in the corn canopy of the two maize species under different planting densities and different nitrogen treatments showed a single peak trend of increasing and then decreasing,and the effect of nitrogen treatment on the NDVI of the two maize species was significant(p<0.05)during the fertility period.At N2 and N3,there was a significant difference in NDVI between the three planting densities from the nodulation stage to the mouth stage with D3>D2>D1.3.ZD958 and XY335 predicted LAI best by fitting power function models to NDVI and LAI in the spit,lactation and waxing canopy.The best predictions were made by the power-function model of NDVI and aboveground biomass in the mature canopy,and the better predictions were made by the different types of models of NDVI and aboveground biomass in the nodulation,spit,lactation and wax maturation periods.The prediction accuracy of the power function model fitted to the canopy NDVI and SPAD was highest at the lactation and wax maturity periods,while the model types fitted to the NDVI and SPAD models were different but had higher prediction accuracy at the nodal and maturity periods.4.A dynamic model suitable for RNDVI dual-logistics was constructed,and the accuracy of the XY335 model was higher than that of ZD958 at a planting density of 37500 plants/hm2,R2 was 0.632 and RMSE was 0.149 for the ZD958 model,R2 was 0.994 and RMSE was 0.101 for the XY335 model,and the accuracy of the ZD958 model was higher than that of XY335 at a planting density of 67 500 plants/hm2,R2 was 0.996 and RMSE was 0.102 for the ZD958 model,R2 was 0.983 and RMSE was 0.122 for the XY335 model.5.At both planting densities,the NO treatment was nitrogen-deficient from nodulation to wax maturity,and the planting density was 37500 plants/hm2.From nodulation to wax maturity,the N1 treatment NNI was slightly less than 1,which was slightly nitrogen-deficient.XY335 was in a nitrogen-deficient state with NNI<1 under N1 and N2 treatment from the spike stage to the wax maturity stage.The planting density was 67,500 plants/hm2,and XY335 was slightly nitrogen deficient with NNI<1 from spike to wax maturity with N1 treatment and N3 treatment with NN1>1,with excessive nitrogen nutrients.In summary,this study clarified that nitrogen application not only promotes the growth and development of maize but also significantly affects the NDVI of maize canopy,and constructed an optimal estimation model between NDVI and maize growth indicators.