Optimizing Agricultural Water Use: A Comparative Analysis of Soil Moisture and Evapotranspiration-Based Irrigation Scheduling for Carrot Crop (Daucus Carota)

Abstract

Crop production in Ethiopia is limited owing to water scarcity. Various technologies and management options are being used for efficient use of the available water resources in crop production. This study evaluated the performance of Soil Moisture (SM) and Evapotranspiration (ET) based irrigation scheduling methods on carrot yield and Water Use Efficiency (WUE), Water Productivity (WP) and field water use efficiency at water scarce areas of Arba Minch for two consecutive years/seasons of 2021 and 2022. The experimental design was a randomized complete block with three replicates. The treatments combined two scheduling techniques (soil moisture, SM, and evapotranspiration, ET). Water was delivered to furrows using an RBC flume, and data was analyzed with ANOVA at 5% significance level using SAS software and the graphs were drawn by Python.  Across 2021 and 2022 seasons, SM-based irrigation consistently required less water than ET-based scheduling, achieving 5–5.4% water savings at full irrigation levels without reducing yields. Under moderate deficit irrigation (50–75%), both methods sustained comparable yields (42–43 t/ha), but SM-based treatments showed higher WUE, FWUE, and WP, with peak values at SM50% (WUE = 31.4 kg/m³; FWUE = 22.7 kg/m³; WP = 1.78 kg/m³) compared to ET50% (WUE = 25.8 kg/m³; FWUE = 18.1 kg/m³; WP = 1.78 kg/m³). Severe deficit irrigation (25%) drastically reduced yield and all efficiency indices in both methods. Economic analysis indicated that moderate irrigation levels (50%) maximized net benefits and cost-benefit ratios. Overall, SM-based irrigation was more efficient in water use, improved yield stability, and enhanced WUE, FWUE, and WP across irrigation levels. Thus, it demonstrated its suitability for sustainable carrot production under limited water resources. This saving is particularly relevant for Ethiopia where water scarcity limits crop production. It demonstrates a practical strategy for farmers to grow more food with less water while supporting sustainable resource management.

Keywords: Soil moisture; Furrow Irrigation; Crop evapotranspiration; ET-Based irrigation; SM-based irrigation