RESUMO
Watermelon productivity in the Arba Minch irrigation scheme has been hampered by water scarcity, with only the Lady Bells watermelon variety being cultivated in the area. This challenge can be mitigated by adopting water-saving irrigation techniques and selecting water stress-resistant varieties. Hence, this study aimed to investigate the combined impact of soil mulching and deficit irrigation on the productivity of various watermelon varieties and validate the AquaCrop model. The experiment employed a randomized complete block design with two levels of water application (100 % SMD and 50 % SMD), two mulching practices (non-mulching and mulching), and four watermelon varieties: Lady Bells (V1), Green Pearl (V2), Kaolack (V3), and Koloss (V4). Soil physical properties and crop-related data were used to calibrate the AquaCrop model. Straw mulching, on average, conserved 64.50 mm and 262.75 mm of water under 100 % and 50 % water application levels, respectively. The minimum and maximum land productivity averages were 6.2 tonsha-1 (T13) and 17.6 tonsha-1 (T2), while water productivity ranged from 5.2 kgm-3 (T1) to 12.4 kgm-3 (T10). Lady Bell watermelon varieties displayed high sensitivity to water stress, with a 1.27 yield response factor under non-soil mulching treatment with 50 % water application. The mean benefit-cost ratio varied from 1.52 (T13) to 2.90 (T10). The average values of RMSE, NSE, and R2 for the AquaCrop model were 0.70, 0.65, and 0.80, respectively, indicating the model's acceptability in predicting the effects of mulching and deficit irrigation on watermelon productivity. Overall, the use of straw mulching combined with 50 % deficit irrigation, particularly for Green Pearl varieties, emerged as the most productive watermelon cultivation method in the Arba Minch region when facing limited irrigation water. Future research will focus on assessing the impact of deficit irrigation during various watermelon growth stages.
RESUMO
Improved irrigation water management is the main strategy to improve water use efficiency in areas with limited water resources. Optimizing scarce water by selecting suitable furrow irrigation systems in arid and semi-arid parts of Ethiopia is rarely practiced. A field experiment was carried out to evaluate the effect of conventional, alternate, and fixed furrow irrigation systems with three levels of irrigation (100%ETc, 75%ETc, and 50%ETc) on maize agronomy and water use efficiency in Arba Minch, Southern, Ethiopia. The experimental study had nine treatments under a randomized complete block design with three replications. Furrow irrigation system and deficit irrigation levels had a significant impact (P < 0.01) on maize agronomy, grain yield, and water use efficiency. The maximum grain yield of 7.99 ton ha-1 obtained under a conventional furrow irrigation system at 100%ETc was significantly higher than the other treatments and the minimum grain yield of 4.24 ton ha-1 obtained under a fixed furrow irrigation system at 50%ETc was significantly inferior as compared to other treatments. The maximum values of crop, field, and expense water use efficiencies were 2.49, 2.80, and 1.72 kg m-3 under conventional furrow irrigation at 50%ETc, respectively. The minimum values of crop, field, and expense water use efficiencies were 1.47, 1.28, and 1.05 kg m-3 under a fixed furrow irrigation system at 100%ETc, respectively. A conventional furrow irrigation system at 50%ETc can increase 0.64 ha net additional irrigable land pre each hectare compared to the conventional furrow irrigation system at 100%ETc. Water saving up to 50%ETc in conventional furrow irrigation can solve the water shortage problem by improving water use efficiency with insignificant yield reduction.