CONCLUSIONS AND RECOMMENDATIONS

Chapter 7 CONCLUSIONS AND RECOMMENDATIONS 7.1 Conclusions 7.1.1 The traditional tillage system. Farmers in Ethiopia use an indigenous plow called Maresha for all stages of tillage. Because of the triangular geometry of the plow, V-shaped furrows are created that leave unplowed strips of land between adjacent passes. In order to deal with the unplowed strips of land, farmers carry out cross plowing. Cross plowing increases the time and energy requirement of seed bed preparation because the plow is moved over the already plowed area in order to access the unplowed parts. Moreover, cross plowing entails laying furrows along the hillslope in one of any two consecutive tillage operations, which can encourage high surface runoff. Farmers start tillage as early as February and continue doing so until July. In most cases, tef fields are plowed 3 to 5 times while maize fields are plowed 3 to 4 times. Farmers realize that repeated plowing with the Maresha Plow causes evaporation losses due to exposure of the lower moist layers. However, they can not avoid plowing which is needed to break the surface crust formed by rainfall that follows a wetting-drying cycle. Moreover, the need for controlling weeds that emerge before planting and that cause loss of soil moisture through unproductive transpiration, forces farmers to plow during dry spells. Farmers do not plow their fields before the rains start to avoid high draft power requirement, excessive pulverization leading to compaction by subsequent rains, higher weed infestation and formation of too many clods. They also want to let weeds emerge for a better control. The main purposes of tillage in the production of maize and tef at Melkawoba and Wulinchity are soil moisture conservation and weed control. Farmers also perceive soil warming as one of the purposes of tillage. Plow pans were found at depths ranging from 0.18 m to 0.25 m. 7.1.2 The Maresha modified conservation tillage implements The implements that were developed as modifications to the traditional tillage implement, the Maresha Plow, were found to be suitable to the respective operations they were developed for while maintaining simplicity, light weight and low cost nature of the traditional plow. The Subsoiler, when operated along furrows made by the Maresha plow, penetrated up to a depth that enables disruption of the hard pan created under the traditional cultivation system. The use of the Row Planter to plant maize resulted in early and twice as much seedling emergence as manual placement of seeds, under moisture stress situations leading to increased grain yields, in addition to saving labor and time by up to 85%. The Tie-ridger made furrows with larger cross sectional areas than those made by the Maresha Plow and the inverted BBM while requiring lower

draft forces. The lifting force required by the Tie-ridger, when tying furrows, was lower than that required by the Maresha plow and the inverted BBM. The Maresha Modified Plow reduced tillage frequency because of U-shaped furrow cross-sections and better weed control. It also increased depth of tillage leading to more infiltration and higher yields. 7.1.3 The locally adapted conservation tillage systems. Reduced water productivity and hence lower crop yields in Ethiopia are caused by the traditional tillage system, which limits the water available to the crop. Among the conservation tillage systems tested on tef the one that involves initial soil opening with the Maresha Plow along the contour leaving narrow unplowed strips at a spacing of 0.75 m followed by one time plowing with the Maresha Modified Plow, subsoiling and planting with the Sweep (ITS) resulted in the least surface runoff, highest transpiration and the highest yields. Water productivity using total evaporation and rainfall were the highest for ITS followed by conventional tillage (CONV) and minimum tillage (MT). Minimum tillage performed worse than conventional tillage because of lower infiltration and higher weed infestation. Among the conservation tillage treatments tested on maize, the one that involved strip tillage at 0.75 m spacing followed by subsoiling and planting over the same lines (STS) resulted in the least surface runoff, highest transpiration and the highest crop yields followed by the one that did not involve subsoiling (ST) and the traditional tillage system (CONV). However, when the time between the last tillage operation and planting was more than 26 days the reverse occurred because of higher weed transpiration and surface compaction by rainfall. The effect was more pronounced with an increase in the cumulative rainfall occurring between the last tillage operations in the STS/ST treatments and planting. A simple conceptual model simulated soil moisture in the root zone better than a physically based model that employed Richards equations. This could be because preferential flows are dominant in the semi-arid tropics while the tested physically based model did not estimate the influences of such flows on the hydrology of the unsaturated zone. Closing furrows in STS/ST treatments gave significantly higher grain yield apparently because of reduced soil evaporation. Fertilization had a significant effect on grain yield of maize except in seasons when there was severe moisture stress. Financial analysis carried out on the average yields of the three years showed that ST was the most profitable tillage system while STS had the highest profitability when the time between the last tillage operation in STS/ST and planting was less than a week. Tillage systems did not result in any significant difference in the physical and chemical properties of the soil. The experiments have shown that it is indeed possible to introduce new insights and new technology into traditional farming systems, provided these innovations increase yields, reduce labor and are affordable. Farmers are eager to adopt a new

technology if these conditions are met and if they are proven to be effective in the field. With the suggested additional research required to fill some of the gaps observed during the study, it is concluded that the tested conservation tillage systems can be applied to increase water productivity and grain production by positively altering rainfall partitioning in the dry semi-arid areas of Ethiopia while being affordable by smallholder farmers. 7.1.4 Participation of farmers in research. Involvement of farmers beginning from the inception of on-farm research benefits both the researcher and the farming community. In addition to tapping their indigenous knowledge and properly managing research fields, involvement of farmers in research boosts their confidence in newly introduced technologies making them enthusiastic to try them by themselves. This has the potential of quicker development and adoption of appropriate technologies. 7.2 Recommendations Based on the consistent performance of the improved tillage system tested on tef, ITS is recommended for popularization among smallholder farmers in semi arid areas. The Maresha modified implements can also be popularized among farmers. The conservation tillage system that was tested on maize and that involved strip tillage followed by subsoiling (STS) has shown promising results when the time between the last tillage operation and planting was less than a week. Additional studies are required to verify the performance of the tillage system paying particular attention to the timing of subsoiling. The use of the sweep that does not expose the lower moist soil while breaking surface crust and controlling weeds during dry spells should be tested further as a means to solve the dilemma that farmers face during the dry extended periods between tillage commencement and planting. Farmers believe that plowing helps to warm up the soil thereby improving seed germination. Further investigation is required to study the effect of plowing on soil temperature and thus on seedling emergence. Farmers’ techniques of tillage timing, which they believe helps improve soil workability and infiltration and reduce soil evaporation should be explored further for possible incorporation in the design of appropriate conservation tillage systems. Studies are required to measure the water balance at a watershed scale, which will enable the measurement of stream flows (surface and rapid ground water flows) that could have an impact on the uniformity of stream flows during rainy and dry periods, through increased infiltration and groundwater recharge, for the benefit of downstream users. Moreover, soil loss studies resulting from the application of conservation and conventional tillage systems should be carried out both on field scale and over watersheds. Further studies are required on preferential flows occurring in semi arid areas of Ethiopia for a better understanding of the hydrology of unsaturated flow.