Assessing the role of rainfall redirection techniques for arresting the land degradation under drip irrigated grapevines

Abstract Altering the soil surface features can potentially regulate water and solute movement processes in the soils, and reduce the accumulation of salts in the plant root zone. In this study, HYDRUS-2D was used consecutively for three years (2011–2014) to evaluate the potential impact of different rainfall redirection and water harvesting techniques such as no mounding or control (A), mid-row mounding (B), mid-row mounding covered with plastic (C), and plastic buried in the soil in mid-row (D) on water balance, root zone salinity dynamics, and salt balance in the soil in three grapevine producing regions (Loxton, McLaren Vale, and Padthaway) in South Australia. Simulations covered varied soil, climate, irrigation quality (0.3, 1.2, and 2.2 dS/m), and vine management conditions typical of each region. Seasonal transpiration (Tp), evaporation (Es), and drainage (Dr) accounted for 39–49, 26–44, and 17–25%, respectively, of the total drip irrigation applied to the vineyards across the three locations. Relative to the control, mounding mid-row soils (B) did not significantly alter the water balance at any site; adding an impermeable plastic layer to that mound (C) reduced Es (48–54%), and increased Dr (by two thirds) and Tp (1–16%). A tremendous ameliorative impact of mid-row mounding with plastic (C) was observed in the spatiotemporal salinity dynamics in the soils at all three locations (salt removal efficiency LEs > 1). An increased leaching fraction under the mid-row mounding with plastic (C) led to considerable (up to 14.6 t/ha) salts leaching from the crop root zone, which was double the other treatments. Buried plastic (D) showed slightly better outcomes than the control or mid-row mounding, particularly for seasonal salt leaching in heavy textured soils. Salt removal efficiency (LEs) > 1 in light- and medium-textured soils as compared to heavy-textured soils indicates better salt removal in the former soils. The results demonstrated that the mid-row mounding with plastic is an effective technique to reduce root zone salinity in the drip-irrigated horticultural crops.