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.
