Effect of conservation agriculture on soil water balance and crop yield for improved dryland farming on vertisols in Northern Ethiopia

Background: In the northern Ethiopian arid and semi arid areas, water shortage is the main constraint to crop production. Changing the current tillage practices with Conservation Agriculture (CA) is one of the options to maximize the rain water use efficiency to increase in situ moisture conservation and thereby increasing crop yield. Hence, a three years (2008 to 2010) study was performed from experimental plots established in 2005 to assess the impacts of different CA practices on the water balance components and crop yield in a Vertisol in a rainfed field in Adigudem, northern Ethiopia. Methods and Materials: The experimental layout was implemented in a randomized complete block design with 3 replications on permanent plots of 5 m by 19 m. The tillage treatments were (i) permanent raised bed (PB) in a furrow and bed system with 30% standing crop residue retention and no-tillage on top of the bed, (ii) terwah tillage system (TER) with ploughing once at sowing with 30% standing crop residue retention and contour furrows made at 1.5m distance interval, and (iii) conventional tillage (CT) with a minimum of three tillage operations and removal of crop residues. All the ploughing and reshaping of the furrows was done using the local ard plough mahresha. Crops grown, from the first to the sixth year sequentially were wheat, teff, wheat, barley, wheat and teff. Glyphosate was sprayed starting from the third year (2007) at 2 L/ha before planting to control pre-emergent weed in PB and RT. The field plots were equipped to monitor all components of the soil–water balance except evapotranspiration, which was computed by solving the water balance equation. Result and Discussion: The results show that PB resulted in the highest increase in moisture storage. The applied CA practices which increased water conservation during the growing period greatly affect barley, wheat and teff yield. Biomass yield in 2008 and 2009 were higher in PB followed by TER compared to CT indicating PB remains unaffected by short dry spells. Rain water loss by Evaporation was found to be higher in CT followed by TER. PB increased consistently precipitation storage efficiency and precipitation use efficiency over the three years compared to CT. Also the systems water use efficiency was significantly higher in PB as compared to CT in 2008 and 2009 while higher in TER in 2010. Conclusion: From data of three consecutive rainy season years (2008 to 2010), it could be concluded that PB resulted in the highest precipitation storage efficiency, precipitation use efficiency and crop yield except teff yield in 2010 was higher in TER. Farmers in the area planted teff late in the cropping season to avoid excessive soil moisture conditions which may explain the presence of lower yield in PB. Planting time adjustments in PB treatments can be possible suggestion to further increase teff yield