| Abstract | Lekitatu irrigation scheme is divided into four areas of irrigation i.e. Ngolo, Absynia, Lenga and Ngarasero II based on intake location. During this study, each area within Lekitatu irrigation scheme was considered as discrete scheme depending on its water source. Based on the above phenomena this study was conducted by examining the scheme water supply versus the irrigation water requirements for all four areas, evaluating to what extent the scheme was performing in relation to irrigation water management. For this, three groups of performance indicators were considered (water balance, agricultural production and physical indicators) and AquaCrop model was later used as a tool for identification of irrigation and field management practices which could be adopted by the farmers to increase the yield and water productivity. Since the scheme was growing various crops, maize and rice crops which are dominant crops were selected for this study. During our study it was found that volume of water supplied at Lekitatu irrigation scheme for a year 2015 was 7.1 Mm3compared to 8.7 Mm3which was required to meet the gross irrigation demand. However each area was examined separately and seasonally, it was also revealed that farmers were abstracting more water than required. The quantity was varying depending on the season, for instance water diverted to Ngolo area was 0.47Mm3in wet season while the demand was 0.27Mm3. Also other areas like Ngarasero II was abstracting 0.28Mm3 less water compared to a demand of 1.36Mm3.Relative water supply for Ngolo, Absynia, Lenga and Ngarasero II were 3.2, 1.3, 1.7 and 0.8 for wet season, and, 2.8, 1.4, 1.8 and 0.8 for dry season, respectively. The relative irrigation supply for Ngolo, Absynia, Lenga and Ngarasero II were 1.7, 1.0, 1.4, and 0.2 for wet season, and, 1.8, 1.1, 1.10.2 for dry season, respectively. Water use efficiency was also computed and it was noticed that it ranged from 0.6 to 3.2for wet season and 0.6 to 2.1for dry season. Land and water productivity in terms of GAVP also ranged from 3500 to 3700 US$/ha for rice,and,200 to 290 US$/ha for maize and 0.08 to 1.4$/m3,respectively. The irrigation ratio and sustainability of irrigated area range from 0.5 to 1.5 and 0.5 to 0.8, respectively,for wet and dry season. AquaCrop model was used to simulate crop yield and water productivity for given irrigation and field management parameters. The model was used to identify the best practices for maize and rice at Lekitatu irrigation scheme in Meru DC, Tanzania. Improved spacing of 75 x 40cm for maize, and 20 x 20cm for rice were evaluated together with irrigation interval, irrigation method, net irrigation depth and field management practices. Results concluded that under plant spacing of 75 x 40cm, irrigation interval of 21 and 14 days during wet and dry season respectively, furrow as irrigation method and 60mm as net irrigation depth, maize could yield up to 2.159 ton/ha. Rice with spacing of 20 x 20 cm, irrigation interval of 21 and 14 days during wet and dry season respectively, basin as irrigation method and 56mm as net irrigation depth, could yield up to 6.481 ton/ha. |