Assessment of strip tillage systems for maize production in semi-arid Ethiopia: effects on grain yield and water balance

Abstract. The traditional tillage implement, the Maresha plow, and the tillage systems that require repeated and cross plowing have caused poor rainfall partitioning, land degradation and hence low water productivity in Ethiopia. Conservation tillage could alleviate these problems. However, no-till can not be feasible for smallholder farmers in semi-arid regions of Ethiopia because of difficulties in maintaining soil cover due to low rainfall and communal grazing and because of high costs of herbicides. Strip tillage systems may offer a solution. This study was initiated to test strip tillage systems using implements that were modified forms of the Maresha plow, and to evaluate the impacts of the new tillage systems on water balance and grain yields of maize (Zea mays XX). Experiments were conducted in two dry semi arid areas called Melkawoba and Wulinchity, in the central Rift Valley of Ethiopia during 2003–2005. Strip tillage systems that involved cultivating planting lines at a spacing of 0.75 m using the Maresha plow followed by subsoiling along the same lines (STS) and without subsoiling (ST) were compared with the traditional tillage system of 3 to 4 times plowing with the Maresha plow (CONV). Soil moisture was monitored to a depth of 1.8 m using Time Domain Reflectometer while surface runoff was measured using rectangular trough installed at the bottom of each plot. STS resulted in the least surface runoff (Qs=17 mm-season⁻¹), the highest transpiration (T=196 mm-season⁻¹), the highest grain yields (Y=2130 kg-ha⁻¹) and the highest water productivity using total evaporation (W_PET=0.67 kg-m⁻³) followed by ST (Qs=25 mm-season⁻¹, T=178 mm-season⁻¹, Y=1840 kg-ha⁻¹, W_PET=0.60 kg-m⁻³) and CONV (Qs=40 mm-season⁻¹,T=158 mm-season⁻¹, Y=1720 kg-ha⁻¹, W_PET=0.58 kg-m⁻³). However, when the time between the last tillage operation and planting of maize was more than 26 days, the reverse occurred. There was no statistically significant change in soil physical and chemical properties after three years of experimenting with different tillage systems.