Enhancing Water Security Through Automated Drip Irrigation: Impacts on Soil Moisture Dynamics and Brinjal Yield in Semi-arid Systems

Abstract

Improving irrigation efficiency is essential for sustaining vegetable production in water-limited environments, yet field-scale evaluations of practical time-based automated drip irrigation systems remain limited. This study compared an Automated Drip Irrigation Treatment (ADIT) employing scheduled time-based irrigation with a Manually Operated Drip Irrigation Treatment (MDIT) under polythene mulch for brinjal (Solanum melongena L.) cultivation in sandy loam soil during the 2025 Yala season in Sri Lanka. Soil moisture dynamics, irrigation uniformity, root distribution, wetting patterns, crop water requirement, yield, and irrigation water-use efficiency (IWUE) were evaluated using field measurements together with CropWat and HYDRUS-1D simulations. ADIT achieved consistently higher irrigation performance, with Christiansen’s coefficient of uniformity (CU) of 91–93%, emission uniformity (EU) of 90–92%, and distribution uniformity (DU) of 88%, compared with 75–80%, 78–82%, and 72%, respectively, under MDIT. Improved water distribution resulted in more stable root-zone soil moisture conditions, while HYDRUS-1D simulations predicted substantially lower deep percolation losses under ADIT than MDIT during crop development. Field observations also showed greater lateral root spread (40.7 cm vs 33.0 cm), higher irrigation water-use efficiency (4.91 vs 3.37 kg m-3), and greater marketable yield (22.3 vs 16.7 t ha-1; 2.35 vs 1.62 kg plant-1) under ADIT. Because the evaluated irrigation configurations differed in hydraulic characteristics as well as irrigation control strategy, and the study was conducted as a single-season field-scale pilot without replicated treatment plots, the findings should be interpreted as comparative evidence of system-level performance rather than effects attributable solely to automation. Nevertheless, the evaluated ADIT configuration demonstrated considerable potential for improving irrigation performance and water productivity under sandy loam, semi-arid conditions, warranting validation through replicated experiments using hydraulically identical irrigation systems.