Effects of deficit irrigation strategies on soil salinization and sodification in a semiarid drip-irrigated peach orchard

Abstract

Deficit irrigation strategies save water, but may enhance soil salinization and sodification when irrigated with low-quality waters. The objectives of this five-year study performed in the middle Ebro Basin (Spain) were to quantify these processes and assess their potential deleterious impact on the response of peach trees subjected to full irrigation (FULL), sustained deficit irrigation (SDI, irrigated at 62.5% of FULL) and regulated deficit irrigation (RDI, irrigated at 50% of FULL in Stage II of fruit development). In relation to FULL, water savings were 40% in SDI and 9% in RDI. Soil salinity (ECe), chloride concentration (Cle) and sodicity (SARe) measured in the saturation extract of 480 soil samples generally increased in the irrigation seasons, particularly in the more severe deficit irrigation strategy (SDI). These increases were counteracted by the leaching of salts induced by high leaching fractions (LF) and low water deficits (WD) attained during the non irrigation seasons. The changes in ECe, Cle and SARe measured between sampling dates were significantly correlated (p<0.01) with WD and LF calculated for the periods between sampling dates. These parameters were therefore suitable to estimate the required irrigation depths for soil salinity and sodicity control. Peach trees were unaffected by the irrigation treatments, but yield productivity tended to decline above a threshold ECe of 4dSm−1. Under the irrigation salinity (mean EC=1.1dSm−1) and the semiarid climatic characteristics of the study area, the three examined irrigation strategies proved to be sustainable in the five studied years.