An Integrated Method for Crop Condition Monitoring

It is possible to evaluate the crop condition and yield status before the harvest for a large scale of area. This paper introduces an integrated method for crop condition together with water shortage monitoring with remote sensing during the crop season. Both NOAA AVHRR and SPOT VGT data are used. VGT data can be used directly since it has been calibrated and corrected before being delivered to the users. AVHRR data are not lucky enough, it need to process on radiance calibration, atmospheric correction,and cloud masking, which generates a consistency AVHRR dataset for the whole China territory since 1991. The non-arable land is masked too in order to highlight the crop information on the arable land. The land use map at a scale of 1:100 000 is used. There are two ways to monitor the crop condition. The differential image of 10 day composite NDVI images in current decade and the same decade in previous year is used to monitor the current crop conditions. The differential image is divided into five categories and assigned with red, yellow, green, cyan and blue to indicate the conditions. Crop condition figures at provincial level are calculated for paddy field and upland area. The result allows users to quickly assess where the crop conditions have been deteriorated, remained or improved. Except for the differential image, the time series of NDVI during the crop season at different scale, such as nation-wide, main production region, province, county, and at different types of paddy field and upland, are used to evaluate the trend of crop condition and compared with the same profile at previous year. The profile also shows the information of crop yield if you look at the peak value, increase or decrease rate, and pattern of curve. A GIS is developed to integrate crop condition information and provide an environment of analysis and evaluation. The GIS can automatically generate the differential image and draw time series of NDVI by retrieving the data from existing database. The ground survey data are integrated into the GIS to review the real situation at field and validate the monitoring results. The meteorological data, like temperature, rainfall, and sunshine duration are integrated too to provide the background information for the analysis. The methods are used to monitor the crop condition over the China since 1998. During the crop season, the bulletin of crop condition are generated every 10 days from later March to Later October. These information are invaluable to decision makers and analysts within government bodies for better management of agricultural production and grain administration. In 1998, China suffered serious flood problem, but the damage to the crop was only limited to narrow areas along the rivers, and the damage were compensated by remote area where had good water supply.