Effet du déficit hydrique sur la croissance, le rendement et l’efficience d’utilisation de l’eau chez la luzerne (Medicago sativa L.) au Tadla

The study of crop response to water deficit is important in areas where water resources are limited. This study was conducted over the period 2009-2011 with the aim to study the effect of water deficit on alfalfa productivity in the irrigated perimeter of Tadla. Under flood irrigation, four water regimes (100%, 80%, 60% and 40% ETc) were compared. Under drip irrigation, the same regimes were associated with spacing between ramps (50 cm and 75 cm). Observations were made on the soil, root system and dry biomass at each cut. The results showed that the average maximum biomass yield was 23.2 T.ha-1. The contribution of the spring cycles to annual yield varies from 55% under 100% ETc to 65% under 40% ETc. In addition to amount of water, alfalfa productivity depend also on the moment when water is applied within a cycle. The water use efficiency varies from one cycle to another and between seasons. It is highest in spring and lowest in winter. Drip irrigation, in comparison with flood irrigation, allows similar biomass yield but with less water and more agronomic efficiency.