Deficit Irrigation for Efficiency and Water Saving in Poplar Plantations

Water resources are increasingly limited and less available, so improving water use efficiency is particularly pressing in the agricultural sector, where inefficient irrigation systems are often in operation. Drip irrigation is one of the most water-saving systems that can optimize distribution according to the actual needs of the crop. In the present study, an engineered drip irrigation system was applied to a poplar crop dedicated to the production of biomass for energy use. The aim was to evaluate the influence of the supply of different volumes of irrigation water on crop growth. Four levels of water supply were tested (theses T1, T2, T3, and T4), each determined by different intervention thresholds established by using four soil moisture sensors, one for each thesis (PLOT) (20, 30, 40, and 50 percent, respectively). In the third growing season, the effect of the different amounts of irrigation water supplied on plant growth was particularly evident between control T1 (104 m3 ha−1) compared with T2 (540 m3 ha−1), T3 (1924 m3 ha−1) and T4 (4549 m3 ha−1). Regarding biomass production, no statistical differences were found between T2 (8.97 Mg DM ha−1 year−1), T3 (9.99 Mg DM ha−1 year−1) and T4 (10.02 Mg DM ha−1 year−1), but they were all different from T1 (7.09 Mg DM ha−1 year−1. This leads to the conclusion, at least up to the third growing season, that with equal satisfactory levels of biomass production, water and energy savings can be achieved by choosing intermediate levels of water supply (e.g., with the sensor at 30%) as compared to the maximum value tested.