Modelling the Impact on Root Water Uptake and Solute Return Flow of Different Drip Irrigation Regimes with Brackish Water

Abstract

Water scarcity and quality degradation represent real threats to economic, social, and environmental development of arid and semi-arid regions. Drip irrigation associated to Deficit Irrigation (DI) has been investigated as a water saving technique. Yet its environmental impacts on soil and groundwater need to be gone into in depth especially when using brackish irrigation water. Soil water content and salinity were monitored in a fully drip irrigated potato plot with brackish water (4.45 dSm−1) in semi-arid Tunisia. The HYDRUS-1D model was used to investigate the effects of different irrigation regimes (deficit irrigation (T1R, 70% ETc), full irrigation (T2R, 100% ETc), and farmer’s schedule (T3R, 237% ETc) on root water uptake, root zone salinity, and solute return flows to groundwater. The simulated values of soil water content (θ) and electrical conductivity of soil solution (ECsw) were in good agreement with the observation values, as indicated by mean RMSE values (≤0.008 m3·m−3, and ≤0.28 dSm−1 for soil water content and ECsw respectively). The results of the different simulation treatments showed that relative yield accounted for 54%, 70%, and 85.5% of the potential maximal value when both water and solute stress were considered for deficit, full. and farmer’s irrigation, respectively. Root zone salinity was the lowest and root water uptake was the same with and without solute stress for the treatment corresponding to the farmer’s irrigation schedule (273% ETc). Solute return flows reaching the groundwater were the highest for T3R after two subsequent rainfall seasons. Beyond the water efficiency of DI with brackish water, long term studies need to focus on its impact on soil and groundwater salinization risks under changing climate conditions.

Laboratory Calibration and Field Validation of Soil Water Content and Salinity Measurements Using the 5TE Sensor

“…Water resources with good quality are limited, resulting in the use of low-quality irrigation water. This can induce soil salinization, leading to crop yield reduction, decreasing the agricultural productivity, and causing general income loss [1,2]. Thus, accurate monitoring of soil salinity in time and space is of great importance for precision irrigation scheduling to save water and avoid soil degradation.…”

“…The 5TE dielectric soil sensor, which also uses the Hilhorst model for ECp estimation, was introduced in 2007 and it is much cheaper than the WET sensor [22]. Several recent studies have investigated the 5TE probe in agricultural applications [2,23,24]. The 5TE sensor has electrodes at the end of the probe that are influenced by soil density making them sensitive to any variation in soil structure and θ content [25].…”

Special Issue “Soil Hydrology in Agriculture”

“…Overall, this study showed the potential of the distributed sensor to provide a more accurate value of soil water content at field scale and to reduce the errors in water balance for shorter wet periods. Slama et al [26] dealt with field measurements and modeling by using Hydrus 1D to evaluate the effect of drip irrigation, irrigation regime on root uptake, root zone salinity and solute return flow to groundwater. Simulations showed that relative yield accounted for 54%, 70% and 85.5% of the potential maximal value when both water and solute stress were considered for deficit, full and farmers' irrigation, respectively.…”

“…Nachshon [35] provided a review on cropland soil salinization, with examples of soil salinization processes from croplands around the world, by discussing the effects of salinity coming from different sources. Slama et al [26] also discussed the effects of different irrigation regimes on root zone salinity. Soil water content and salinity were monitored in a fully drip-irrigated potato plot with brackish water (4.45 dS/m) in semi-arid Tunisia.…”

Impact of rainfall structure and climate change on soil and groundwater salinization

“…Rajmohan and Elango (2007) used HYDRUS-2D (Šimùnek et al 1999) to simulate both nitrate and chloride transport in the vadose zone and to estimate their respective solute fluxes towards groundwater. Slama et al (2019) applied HYDRUS-1D to assess the impact of different drip irrigation regimes with brackish water on soil salinization and solute return flow. 1D unsaturated models are helpful when studying solute return fluxes to groundwater, but the integration of their results to a hydrogeological model is not an easy task.…”