Effect of Soil Tillage Systems on Soil Hydrological Processes in Common Bean (Phaseolus Vulgaris L.) Farms in Mukono District, Uganda
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Date
2021-07-13
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Addis Ababa University
Abstract
Goal 15 of the United Nations 2030 Agenda for Sustainable Development addresses the
protection, restoration, and promotion of sustainable use of terrestrial ecosystems by halting and
reversing land degradation. Soil tillage is one of the main factors causing land degradation in sub
Saharan Africa. In this study, the effect of soil tillage systems on infiltration rate, soil moisture
content, soil water storage, surface runoff volume, suspended sediment concentration, and
sediment yield in common bean (Phaseolus Vulgaris L.) farms, at Goma and Kimenyedde
experimental sites in Mukono District, Uganda was evaluated. The study also assessed the effect
of soil tillage systems on grain yields, water use efficiency, and economic returns of the common
beans. The study further evaluated the performance of the Agricultural Policy/Environmental
eXtender model in the simulation of surface runoff volume and sediment yield. The soil tillage
systems were: no-tillage, stubble-mulching, deep tillage, and conventional tillage. Field
experiments were arranged in Complete Block Design under four soil tillage systems, consisting
of two tillage directions: tillage down the slope and tillage perpendicular to the direction of slope
during three wet seasons. The results showed the highest and lowest infiltration rate and soil
moisture content under no-tillage and conventional tillage, respectively. No-tillage and stubblemulching
improved soil water storage by 46 and 45%, respectively, compared with conventional
tillage in the 0-100 cm soil depth over the 16 months. The highest surface runoff volume was
observed during the third season at Goma site under conventional tillage with tillage down the
slope (1082 mm), while the lowest surface runoff volume was observed during the second season
in Kimenyedde site under no-tillage (165 mm). Tillage perpendicular to the direction of slope
reduced surface runoff volume by the range of 5-15%, relative to tillage down the slope. The
highest and lowest suspended sediment concentration were observed under conventional tillage
(2.65 ± 0.5 g L-1) at Goma site during the third season and no-tillage (0.43 ± 0.1 g L-1) at
Kimenyedde site in the second season, respectively. Sediment yield was highest under
conventional tillage at Goma (183.01 kg ha-1) during the third season and lowest under no-tillage
(9.19 kg ha-1) at Kimenyedde site, during the second season. Soil tillage systems significantly (p
< 0.05) affected water use efficiency, with water use efficiency values generally greater under
no-tillage and stubble-mulching than under deep tillage and conventional tillage. Grain yield was
highest under no-tillage and stubble-mulching than deep tillage and conventional tillage, with
over 5, 38, and 43% higher grain yield under no-tillage than under stubble-mulching, deep
tillage, and conventional tillage, respectively. Seasonal precipitation distribution considerably
influenced crop yield, soil water storage, and water use efficiency. The net profit was three and
five times higher under no-tillage than under conventional tillage and deep tillage, respectively.
No-tillage and stubble-mulching were the optimum soil tillage systems for increasing infiltration
rate, soil water storage, enhancing water use efficiency, improving grain yield and economic
returns in central Uganda. Evaluation of Agricultural Policy/Environmental eXtender model
performance for surface runoff volume and sediment yield simulation provided good results. For
both calibration and validation periods, Nash-Sutcliffe efficiency values were > 0.5, coefficient
of determination > 0.6, and percent bias values were within ±20% for surface runoff volume and
sediment yield. The Agricultural Policy/Environmental eXtender model can be a useful tool for
evaluating surface runoff volume and sediment yield for different management practices in
Mukono District. Adopting no-tillage and stubble-mulching would be efficient strategies for
controlling excessive surface runoff and sediment in the region.
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Keywords
Effect of Soil, Tillage Systems, Soil Hydrological Processes, Common Bean (Phaseolus Vulgaris L.), Farms in Mukono District, Uganda