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

Roberto De Mascellis,Fethi Bouksila,Rachida Bouhlila,Fairouz Slama,Nessrine Zemni

doi:10.3390/w11030425

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.

Highlights

In arid and semi-arid regions, the growing population is facing water scarcity and climate change hazards
Observed data demonstrated that salinity increased in the root zone during the crop season under irrigation with brackish water
As a consequence observed yields were lower than the optimum ones recorded in the region for the potato crop for both full and deficit irrigation treatments

Summary

Introduction

In arid and semi-arid regions, the growing population is facing water scarcity and climate change hazards. In Tunisia, the agricultural sector accounts for a significant share of water resources and irrigation accounts for almost 80% (about 2100 m3 ·y−1 ) of the total water demand [1]. Higher crop production and higher water use efficiency are usually achieved simultaneously with drip irrigation compared to other surface irrigation methods [4]. Among other irrigation methods, as a suitable technique in arid and semi-arid countries to irrigate row crops [5]. The purpose of introducing drip irrigation was to modernize the agricultural production systems and to save water in the context of water scarcity [6].

Objectives

Results

Conclusion