ASSESSMENT AND EFFECTS OF FERTILIZER AND IRRIGATION LEVEL ON MAIZE (Zea mays L.) PRODUCTIVITY AT BOLOSO SORE DISTRICT, SOUTHERN ETHIOPIA

Maize productivity under irrigation is affected by several factors including climate, soil and water management, quality of water and soil, and levels of irrigation and fertilizer application. This study consisted of four objectives to (1) analyze rainfall and temperature variability and change, (2) assess farmers' preferences for soil and water management practices, (3) assess the quality of water and soil, and (4) determine the effects of fertilizer and irrigation levels on maize productivity, for climate change adaptation in Boloso Sore district, southern Ethiopia. Climate variability and change were analyzed using the coefficient of variation, and Mann-Kendall trend test, respectively. The climate was analyzed for the past (1990-2019) and future (2030s, 2050s, and 2070s, under two representative concentration pathways; RCP4.5 and RCP8.5). Farmers' preferences for soil and water management (SWM) practices were analyzed using Multivariate Probit Model. The chemical properties of water and the physicochemical properties of soils were analyzed using standard procedures. Three irrigation levels (70, 85, and 100% crop evapotranspiration; ETc) and four fertilizer rates (0, 50, 100, and 150 kg ha-1) of blended fertilizer (nitrogen, phosphorous, sulfur, and boron; NPSB), were used for field experiments in 2020 and 2021. Randomized complete block design in factorial arrangement with three replications was followed. The impacts of climate variability and change on maize yield were analyzed for 2030, 2050, and 2070 using the AquaCrop model. The results indicate that past rainfall showed medium to very high variability (coefficient of variation; CV ≤ 38.4%), with a non-significantly increasing trend except for Belg. Past maximum temperature (Tmax) and minimum temperature (Tmin) showed low variability, with an increasing trend. Future rainfall has medium to very high variability and deviates from the baseline by up to -1.9% by 2030s, -2.4% by 2050s, and by +2.4 by the 2070s. This trend is confirmed in Belg and Kiermt seasons. A non-significantly decreasing trend of rainfall is expected in the 2030s and 2050s, with an increasing trend by 2070s. From the baseline, Tmax and Tmin would deviate by 0.7-1.2°C by 2030s, 1.3-2.2°C by 2050s, and 1.5-3.2°C by 2070s, under both RCPs. Farmers perceived that irrigation water improved their adaptive capacity to the impacts of climate change by increasing their net income (88%). Their preferences for soil and water management (SWM) practices were xviii significantly positively (p