Effect of different soil moisture regimes on yield and water use efficiency of groundnut at Kobo irrigation scheme, Kobo Ethiopia

In the arid and semi-arid part of Eastern Amhara, water is the most important yield-limiting factor for agricultural production. Application of the right amount of irrigation water at a right time helps to optimize water loss and increases crop yield. Therefore, a field experiment was conducted at Kobo irrigation scheme to determine the optimal crop water requirement and irrigation frequency for yield and water use efficiency of groundnut. The CROPWAT model could generate the 100% irrigation scheduling as 40 mm irrigation water with 8 days. Field base validation and ground truthing is vital. Therefore, the treatments were formulated by the factorial combinations of the three crop water levels as 75% ETc (30 mm), 100% ETc (40 mm), 125% ETc (50 mm) with three irrigation intervals (6 days, 8 days and 10 days). The treatments arranged in randomized complete block design with three replications. The statistical analysis was carried out using Genstat 15.0 software and the mean comparison was done using least significant difference (LSD) test. The analysis revealed that the crop water use efficiency was significantly (p<0.05) affected by the main effects of crop water levels, irrigation interval and by their interaction, whereas the grain yield does not show a significant (p>0.05) response. As the water levels declined and the irrigation intervals varied, the grain yield tends a fairly constant trend. However, based on the commerciality of the crop, application 75% ETc (30 mm) with 8 days irrigation interval gave numerically maximum grain yield of 3466.9 kg/ha and it has nearly more than 200 kg relative yield advantage over most treatments. The highest water use efficiency (0.9 kg/m(3)) was recorded from the combination 75% ETc (30 mm) with 10 days; while it was statistically at par with 75% ETc with 8 days interval (0.8 kg/m(3)) applied treatment. From the result, it could be concluded that the maximum yield and maximum water productivity were simultaneously achieved by combined application of 75% ETc with 8 days interval and saves 4600 m(3 )water to irrigate an additional 1.2 ha compared with 125% (50 mm) ETc with 6 days interval applied treatment.