Study On Yield Estimation Of Main Crops By Remote Sensing Technology Over The Middle Reaches Of Heihe River Basin

Heihe River Basin is the second largest inland river and an important commodity grain production base in China.The climate and water conditions in the middle reaches of the Heihe River Basin are most suitable for the growth of crops.The main crops’yield,such as maize and wheat,were cultivated in the study.Knowing the production and distribution of major crops is of great importance to the development of strategies and plans on agriculture or economy by relevant national authorities.There are many methods to estimate crops’ production using remote sensing technology.By comparing with others,the CASA model has many advantages,such as less input parameters,stronger mechanism and more accurate results,it was used to estimate the crops’ yield in the middle reaches of Heihe River Basin.The climate of the study area is dry,and irrigations offers main water for crops’ growing.In early studies,irrigation factor was not taken into the model,so this study will make some changes.Based on CASA model,software like ArcMap and ENVI,data about meteorology and remote sensing,we first estimated the NPP in the middle reaches of the Heihe River Basin,and verified the adaptability of the model in the study area.Then estimated the crops’ yield.The main contents and conclusions of this paper are as follows:1 The paper analyzed the research progress of remote sensing estimation technology in the middle reaches of Heihe River Basin.Based on the CASA model,main crops’ yield was estimated,including corn,wheat,rapeseed and barley.It has the phenomenon of "northwest lower and southeast higher" on the spatial distribution of crop production in this region.2 Processing methods for input data of the CASA were studied,thin plate smooth spline interpolation method was used to interpolate the data of temperature and rain,an area solar radiation tool of ArcMap was applied to data of solar radiation.3 To express the estimation results clearly and intuitively,we made use of remote sensing digital mapping technology designing the presentation and chosen methods of thematic map elements and colors and mapping the distribution map of the four major crops in 2007,2012 and 2014.4 In order to obtain irrigation factor,the volume of irrigation was estimated in the study area,and added to the CASA model to promote it.By comparing with the estimated NPP and other results,it proves the estimate value locate in a reasonable interval.Then analyzed the correlation to MOD17-NPP.The results show that the model is better after adding the irrigation factor,and the accuracy of the estimation is higher.5 To analyze the relationship between crops’ accumulation process and NDVI,this paper estimated the monthly yield of each crop based on the CASA model,and made compare with them.Indicating that the correlation between crop yield and monthly NDVI is significant,and then indicated that NDVI has a very significant linear correlation with crop yields.