Orientation and root trench effects of Eucalyptus globulus boundary plantations on barley yield and soil physicochemical properties in the Gummer district, Central Highlands, Ethiopia

The expansion of Eucalyptus globules boundary plantations (EGBPs) along farm boundaries is considered to have effects on the yield of crops underneath them. We evaluated the orientation and root trenching effect of EGBP on barley yield and soil physicochemical properties in the Gummer District of Central Ethiopia. Two months before sowing, trenches were prepared on each side of the orientation of EGBP at distances of 0.5 m, 1 m, and 1.5 m using a split-split plot design with three replications. At a 1.5 m trench distance, the north-facing field showed 20.4% to 31.2% additional yield increment compared with the south-, east-, and west-facing fields. Additionally, 15.2% to 43% additional yield was observed as the field distance from the EGBP increased from 3 to 12 m. In comparison to un-trenched fields, trenched fields showed 31.9% to 73.4% additional yield variation. Regarding the soil physicochemical properties, the aspect of EGBP had no a significant effect. However, except for the texture, pH, and exchangeable K, the soil OM, TN, available P, and CEC status significantly differed among the trenches. On average, the root trench minimized the field distance effect of EGBP on barley yield by 24%. Tree root trenching is a potential tool for managing below-ground competition. Therefore, establishing a 0.5 m × 0.5 m trench at a 1.5 m distance from the EGBP is vital for maximizing barley yield and increasing land-use efficiency.