Response of Yield and Water use efficiency to different Irrigation Levels under Furrow systems of Soybean

Introduction: 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 ۶۰ to ۱۰۰% 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. Materials and Methods: This experiment has been executed in Jawi district of Amhara location. Jawi district is found at ۶۰۲ km North West of Addis Ababa with a geographical location of ۳۶o ۲۹’۱۷.۵۸’’ longitude and ۱۱o ۳۳’۲۲.۶۸’’ latitude. It is characterized with hot to humid climate of low land area with high unimodal rain fall (۱۲۵۰ mm) from May to October. Jawi district is located in the lowland part of Awi zone and its altitude ranges from ۷۰۰ to ۱۵۰۰ m.a.s.l with mean yearly temperature of ۱۶oC to ۳۲oC. 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 ۵.۵۲ mm day-۱. 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 ۳ replications was used and contains ۳ furrow irrigation methods (Conventional Furrow Irrigation (CFI), Alternative Furrow Irrigation (AFI), and Fixed Furrow Irrigation (FFI)) as main plot and three DI levels (۱۰۰%ETc, ۷۵%ETc, and ۵۰%ETc) as sub-plot. Results: The result showed that DI had a significant effect on soybean above ground biomass and a very high significant (P<۰.۰۰۱) effect on grain yield. The advanced grain yield of ۱۹۴۴ kg/ha was obtained from CFI at ۱۰۰% of ETc and the minimal one was recorded in FFI at ۵۰% ETc. The highest CWUE of ۱.۱۷ kg/m۳ was obtained from AFI at ۱۰۰% ETc. The highest yield reduction in this experiment was obtained at AFI at ۱۰۰% of the crop water application which showed ۷.۴۶% yield reduction and also saved ۴۷.۹% irrigation water as compared to CFI. Using this saved water, ۳۵% grain yield was obtained under an AFI compared to CFI. Conclusions: It could be reported that enhanced water saving and CWUE might be achieved using ۱۰۰% ETc at AFI system solving water shortage problem. It can be concluded that, in areas where water is scarce alternative furrow irrigation saves ۵۰% 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.

Keywords:

Water Productivity , Crop water use efficiency , Deficit irrigation , Furrow irrigation systems , soybean