EVALUATION OF OPTIMAL IRRIGATION REGIME AND SOWING DATE FOR WHEAT (Triticum aestivum L.) AT MELKASSA, CENTRAL RIFT VALLEY OF ETHIOPIA

Abstract

Water is essential for crop production, and any shortage has an impact on final yields. Reasonable irrigation scheduling and optimum sowing date are key factors for increased crop yield and water use efficiency. A study was undertaken to determine the effects of irrigation regimes and sowing dates on grain yield and water use efficiency of wheat at Melkassa Agricultural Research Center. Five sowing dates, i.e. October 1, October 15, November 1, November 15 and December 1 were used as a main plot and three irrigation levels (75%, 100% and 125% available soil moisture depletion levels) were used as sub plots. Split plot design with three replications was used for the experiment. Analysis of variance indicated that number of days to 90% maturity was significantly (P<0.05) affected by the interaction effects of sowing dates and irrigation levels. The highest number of days to maturity (104.33 days) was recorded for October 1st sown wheat with 75% available soil moisture depletion level and the lowest (92 days) was recorded for December 1st sown wheat at 125% available soil moisture depletion level which were statistically different from all other treatments. Grain yield and water use efficiency were significantly (P<0.01) affected by main effects of sowing dates and irrigation levels. November 1st sown wheat had maximum grain yield of 4576.9 kg ha-1 and 75% irrigation level gave significantly the highest grain yield of 3922.1 kg ha-1 in comparison with other irrigation levels. Water use efficiency was maximum for November 1st sown wheat which gave 94.74 kg ha-1 m-3. Among irrigation levels, the 75% available soil moisture depletion level gave 77.25 kg ha-1 m-3 of water use efficiency which is statistically different from other irrigation levels. The interaction effects of sowing date and irrigation level were significant on plant height (P<0.01) and thousand kernels weight (P<0.5). The tallest plant height (83.87 cm) was recorded from October 15th sown wheat at 75% available soil moisture depletion level which was statistically at par with November 1st sown wheat at all available soil moisture depletion levels. The highest thousand kernels weight (38.6 g) was obtained from October 1 at 125% available soil moisture depletion level. Results from the study revealed that maximum grain yield and water use efficiency could be achieved with wheat sown on November 1 at 75% available soil moisture depletion level and any delay in wheat sowing and increase of available soil moisture depletion level might reduce wheat yield in the study area