Monitoring Of Drought Index And Drought Information Of Silage Summer Maize By UAV Remote Sensing

Unmanned aerial vehicle(UAV)remote sensing can obtain high-precision drought information quickly,which is great significance to the promotion of new water-saving irrigation technology.In this study,the silage Summer Maize in Zhaojun Town experimental station of Dalat Banner,Inner Mongolia,in 2018 was taken as the research object.The multispectral and thermal infrared image data were obtained by UAV remote sensing system.The vegetation index and surface mixed temperature were extracted to determine the land temperature difference,Temperature Vegetation Drought Index(TVDI)and water deficit index(WDI)to monitor the silage summer maize drought.The correlation between drought index and soil water content/stomatal conductance under different time scales and water stress during the period was studied.and the differences between the inversion models of drought index and soil water content/stomatal conductance established by different methods were compared.The main research contents and conclusions are as follows:(1)Raw data acquisition and drought index calculation.The meteorological data and field surface data are acquired by ground equipment;the multi-spectral and thermal infrared images are acquired by UAV remote sensing system;the orthophoto images of experimental fields are acquired by remote sensing image pretreatment,and the normalized vegetation index(NDVI),enhanced vegetation index(EVI),soil-regulated vegetation index(SAVI)and surface mixed temperature are extracted.Drought index was calculated by combination.(2)The monitoring effect of land temperature difference on Silage summer maize drought was studied.The results show that the land temperature difference map can distinguish bare land,maize and irrigated areas.In different growth stages,the difference of land temperature can monitor the change of Maize Drought on the diurnal and ten-day scales.Under different water stress,the difference of land temperature can not monitor the drought of silage summer maize under 100% full irrigation;65% and 40% full irrigation,the difference of land temperature fluctuates greatly during the jointing stage,and the effect of monitoring the drought in the middle and late growth stage is stable.(3)The monitoring effect of Temperature Vegetation Drought Index on Silage summer maize drought was studied.The results show that TVDI distribution map can clearly distinguish bare land,maize and irrigated areas.At jointing stage,TVDI is suitable for monitoring maize drought at daytime scale;at 10-day scale,TVDI is ineffective for monitoring drought;under different water stress,TVDI can not monitor drought steadily.TVDI can be used to monitor maize drought at daytime scale in the middle and late growing period;TVDI calculated by NDVI and SAVI can be used to monitor soil moisture content in ten-day scale;TVDI calculated by SAVI can be used to monitor maize stomatal conductance;TVDI can not monitor maize drought under 100% full irrigation under different water stress;TVDI calculated by SAVI can be used to monitor maize drought stably under 65% and 40% full irrigation conditions.Change of soil moisture content.(4)The monitoring effect of water deficit index on Silage summer maize drought was studied.The results showed that WDI distribution map could clearly distinguish bare land,maize and irrigated areas.At jointing stage,WDI is suitable for monitoring drought changes at daytime and ten-day scales.Under different water stress,WDI can not monitor drought of Maize under 100% full irrigation,and WDI can monitor drought changes steadily under 65% and 40% full irrigation.WDI can be used to monitor maize drought at daytime scale in the middle and late growing period,and WDI calculated by NDVI and SAVI can be used to monitor the change of soil water content at ten-day scale.Under different water stress,WDI can not monitor maize drought stably.(5)The correlation of three drought indices with soil moisture content and stomatal conductance was analyzed and compared.The results showed that the land temperature difference and temperature vegetation drought index were more advantageous in monitoring the drought of silage Summer Maize at daytime scale,while the water deficit index was suitable for monitoring the drought at jointing stage and the land temperature difference was suitable for monitoring the drought at middle and late growth stages.(6)Different inversion models of drought index and soil moisture content and stomatal conductance were compared.The results show that the support vector machine model of landair temperature difference can significantly improve the inversion effect and scope of application;the support vector machine model of temperature-vegetation drought index can steadily improve the inversion effect;and the support vector machine model of water deficit index can effectively improve the inversion effect.