Subsurface Hydrological Processes and Surface Irrigation Management.

Irrigation water use efficiency need to be continuously improved to meet the world growing food demand. Subsurface hydrological processes and pedological features influencing them (drainage, leaching, presence of a compacted layer, root development) act at different spatial scales and are generally neglected in managing irrigation at the whole field scale, in absence of adequate identification and quantification of their influence. Real time GPS equipped monitoring tools now allow us to identify the effect of capillary rise, compacted zones or differential crop water uptake on the surface water potential and the consequent irrigation needs acting at different spatial scales. Ongoing research taken from surface and subsurface irrigated crops (lettuce and cranberry) indicates that important water savings (30 to 80%) and gain in water and crop productivity (50%) can be achieved by implementing procedures that take into account subsurface processes in managing surface irrigation of crops. Given these results, long-term efforts should be put to implement such approaches at the farm scale.