Combined use of FORMOSAT-2 images with a crop model for biomass and water monitoring of permanent grassland in Mediterranean region

摘要

The aim of this study is to propose methods to improve crop and watermanagement in Mediterranean regions. At landscape scale, there is a spatial variability of agricultural practices, particularly forgrasslands irrigated by flooding. These grasslands are harvested three timesper year and produce high quality hay, but their productions decreasedsignificantly during the last few years because of the water scarcity. It istherefore important to assess the real water requirement for crops in orderto predict productions in the case of agricultural practice modifications.Until now, the spatial variability of agricultural practices was obtainedthrough surveys from farmers, but this method was tedious to describe anentire region. Thus, the specific aim of the study is to develop and assess a newmethod based on a crop model for estimating water balance and crop yield constrained by products derived from optical remote sensing data with high spatio-temporal resolution.A methodology, based on the combined use of FORMOSAT-2 imagesand the STICS crop model, was developed to estimate production, evapotranspiration and drainageof irrigated grasslands in "the Crau" region in the South Eastern France.Numerous surveys and ground measurements were performed during an experimentconducted in 2006. Simple algorithms were developed to retrieve the dynamicof Leaf Area Index (LAI) for each plot and the main agricultural practicessuch as mowing and irrigation dates. These variables computed from remote sensing were then used toparameterize STICS, applied at region scale to estimate the spatialvariability of water budget associated with the biomass productions. Resultsare displayed at the farm scale. Satisfactory results were obtained whencompared to ground measurements. The method for the extrapolation to otherregions or crops is discussed as regard to data available.