The Institute for Agricultural research (IAR), Zaria has developed and released some improved sorghum varieties that are early maturing, but their performances under irrigation and water limited areas has not been widely investigated. The study aimed to determine the effect of deficit irrigation and Nitrogen rates (N-rates) on yield, seasonal crop water use and yield response factor of three sorghum varieties (Samsorg 40, Samsorg 45 and Samsorg 49).The experiment was carried out in a randomized complete block design with split-plot arrangement with three replications at three different irrigation water depths (I100%, I75% and I50% of weekly reference evapotranspiration) and three N-rates (N100%, N75% and N50% of fertilizer recommended rate of 60 kg N/ha : 30 kg P/ha : 30 kg K/ha). Irrigation depths were assigned to main plots while sorghum varieties and N-rates were allocated to sub plots. The crop Yield varied between 1.08 to 2.93 t/ha for Samsorg 40, 1.04 to 3.59 t/ha for Samsorg 45, and 0.86 to 1.91 t/ha for Samsorg 49.The seasonal crop water use (SCWU) ranged from 250.6 to 471.4 mm for Samsorg 40, 302.9 to 490.0 mm for Samsorg 45 and 277.9 to 454.2 mm for Samsorg 49.The yield response factor (Ky) was found to be 0.79, 0.65 and 1.26 respectively for Samsorg 40, Samsorg 45 and Samsorg 49. Samsorg 45 variety performed best interms of yield and exhibited more water stress tolerance (Ky = 0.65) compared to the others, hence is recommended for water-limited environments.
Key words: Sorghum varieties, Irrigation water application regimes, Nitrogen application rates, yield, Seasonal crop water use and yield response factor
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