“…Pioneering work carried out in this field, such as by Fischer (1975), found that wheat yields could be forecasted as a function of the leaf area at the onset of the reproductive stage, which corresponds to the timing of maximum crop green leaf area. In the case of wheat, studies have found a strong correlation between the peak of the Normalized Different Vegetation Index (NDVI, Rouse, 1974), which corresponds closely to the reproductive stage, and final wheat yields (Groten, 1993;Mahey et al, 1993;Rasmussen, 1992;Smith, Adams, Stephens, & Hick, 1995;Tucker, Holben, Elgin, & McMurtrey, 1980). Nevertheless, one of the challenges in crop forecasting over large areas, such as at the state or national scale using remote sensing data, is the variability in climatic zones, which can result in different timing of crop development.…”