Water management practice that is, deficit irrigation (DI) has a greater contribution to water-saving and increase crop water use efficiency (CWUE). DI is an approach where crops are exposed to a certain level of water stress either during a specific crop growth stage or in the course of the entire developing season. Furrow irrigation system requires a lower initial investment than other water application systems. However, it is usually associated with considerable runoff and excessive filtration at the upper portion of the furrow while it also causes insufficient application at the lower fields. The DI level to improve water productivity range is between 60 to 100% of full crop evapotranspiration (ETc) needs in previous works. Enhancing water use efficiency of irrigated crops through field irrigation management is vital in water-scarce areas. The DI and furrow irrigation systems are alternatives to enhance CWUE in such areas.
This experiment has been executed in Jawi district of Amhara location. Jawi district is found at 602 km North West of Addis Ababa with a geographical location of 36o 29’17.58’’ longitude and 11o 33’22.68’’ latitude. It is characterized with hot to humid climate of low land area with high unimodal rain fall (1250 mm) from May to October. Jawi district is located in the lowland part of Awi zone and its altitude ranges from 700 to 1500 m.a.s.l with mean yearly temperature of 16oC to 32oC. The climate of Jawi is Kola according to Ethiopian agro ecological climate classification and is equivalent to hot humid climate. The average annual potential evapotranspiration of Jawi is 5.52 mm day-1. A field experiment was worked out in Jawi district of Amhara region of Ethiopia with the objective of investigating the performance of various furrow irrigation techniques and DI levels to enhance the grain yield and CWUE of soybean. Split-plot design with RCBD arrangement in 3 replications was used and contains 3 furrow irrigation methods (Conventional Furrow Irrigation (CFI), Alternative Furrow Irrigation (AFI), and Fixed Furrow Irrigation (FFI)) as main plot and three DI levels (100%ETc, 75%ETc, and 50%ETc) as sub-plot.
The result showed that DI had a significant effect on soybean above ground biomass and a very high significant (P<0.001) effect on grain yield. The advanced grain yield of 1944 kg/ha was obtained from CFI at 100% of ETc and the minimal one was recorded in FFI at 50% ETc. The highest CWUE of 1.17 kg/m3 was obtained from AFI at 100% ETc. The highest yield reduction in this experiment was obtained at AFI at 100% of the crop water application which showed 7.46% yield reduction and also saved 47.9% irrigation water as compared to CFI. Using this saved water, 35% grain yield was obtained under an AFI compared to CFI.
It could be reported that enhanced water saving and CWUE might be achieved using 100% ETc at AFI system solving water shortage problem. It can be concluded that, in areas where water is scarce alternative furrow irrigation saves 50% irrigation water in comparison to conventional furrow irrigation method. Hence, additional land could be irrigated with the saved irrigation water in similar water scarce areas. This finding could make certain the possibility of irrigation improvement in the study area and other comparable agro-ecology like the study area.