A new irrigation priority index based on remote sensing data for assessing the networks irrigation scheduling

Irrigation scheduling has become an important tool that significantly influences growth, development and production of crops, especially in arid and semi-arid regions of the South Mediterranean. In these regions, most of the irrigation scheduling of the gravity irrigation networks are not optimized in terms of timing and water quantity. In this paper, we present a way of characterizing the irrigation distribution by the extensively used irrigation systems through a new irrigation index: the “irrigation priority index” (IPI). This normalized indicator takes into account the water stress coefficient and the time of irrigation with regard to the duration of an irrigation round. The IPI ranges between −1 and 1 and decreases with irrigation priority.The IPI was used to evaluate the actual irrigation scheduling in an irrigated perimeter of 2800 ha of Tensift Al Haouz plain close to Marrakech in Morocco during the 2002–2003 winter wheat season. The obtained results showed that about 32% of the R3 zone plots receive late irrigation, when the stress was maximum (IPI less than −0.3). The sensitivity of grain yield to the IPI values was evaluated on a data set of wheat yields acquired on the 2008–2009 season. The spatial yield was simply calculated using a linear relationship between wheat yields and the spatial accumulated NDVI (Normalized Difference Vegetation Index) of the last 10 days of March (R2 = 0.84). The result showed a clear relationship between grain yield and IPI. Indeed, with significantly positive IPI [0.37, 0.63], production ranged from 3.8 to 4.7 t/ha, whereas, it was less than 2.6 t/ha when the IPI values are ranged from −0.52 to −0.16.

► The assessment of the networks irrigation scheduling is presented.
► A new irrigation index named irrigation priority index; IPI based on NDVI has been used.
► IPI was used to evaluate the actual irrigation scheduling of winter wheat in Morocco.
► The sensitivity of grain yield to the IPI was evaluated in this study.