Effects of soil tillage on runoff generation in a Mediterranean apricot orchard

Two different soil tillage practices (perforated topsoil and mini-catchments) were compared with no tillage (control) in an assay to reduce runoff, promote infiltration and take advantage of rainfall in a drip irrigated, hillside apricot orchard under semi-arid Mediterranean conditions. In addition, the efficiency of water harvesting was quantified for the purpose of saving irrigation water. To predict runoff generation in the three treatments, the best fit was obtained with a two-parameter exponential model, which included the product of rainfall amount and rainfall intensity as independent variable. The model explains, on average, 92% of runoff generation for three soil tillage treatments. The antecedent soil moisture content may account for part of the unexplained runoff generation. More than 30% of the rainfall was lost by runoff in the control treatment, underlining the potential risk of sloping plantations for water and soil conservation. Both soil tillage treatments (mini-catchments and perforated topsoil) decreased the runoff by an 80% compared to the control treatment. During the experimental period, the mini-catchment treatment collected 86% and the perforated topsoil 57% more than the control, providing mean irrigation water saving of about 11 and 9%, respectively. Even these relatively modest figures are very valuable in South-east Spain which suffers from severe droughts.