Soil erosion control and moisture conservation using contour ridge tillage in Bougouni and Koutiala, southern Mali

Soil erosion is among the critical environmental constraint for crop production in southern Mali. Contour ridge tillage (CRT), a water conservation technique had been locally applied since 1990. The objective of this study was to determine the effects of CRT compared with farmer conventional agriculture practice (NoCRT) on runoff, soil loss, nutrient loss, moisture conservation and cereals yields under rainfed conditions in two Southern Mali sites, in 2016 and 2017 in farmer fields. Measurements were performed on erosion plots composed of CRT and NoCRT plots from which water samples were collected to determine sedimentation levels, concentration and nutrients losses using pairwise comparison. Average runoff coefficient in NoCRT plots was 35.62% compared to 19.25% for the CRT plots explaining a runoff reduction of 46%. Mean soil losses of 12,095 t·ha−1 and 4970 t·ha−1 were respectively measured in NoCRT and CRT plots. Losses in calcium, magnesium and potassium nutrients in the NoCRT plots were 80%, 66%, 75% higher compared to CRT ones, respectively. Sorghum grain yield was at least two folds higher in CRT plots compared to the NoCRT plots. Maize average grain yield was 87% higher in CRT plots than in the NoCRT. For sustained soil productivity, CRT is advocated as a better soil and water management technique than the NoCRT one

Hydrological modelling of sustainable land management interventions in the Mizewa watershed of the Blue Nile basin

The current paper discusses the use of hydrological modelling tool to understand sustainable land management interventions in the Blue Nile basin of Ethiopia. A micro-watershed named Mizewa with a drainage area of 27 km2 in Fogera district was selected and instrumented with hydrological cycle observation networks in the year 2011. The SWAT hydrological modelling tool was used to simulate landscape-wide Soil and Water Conservation (SWC) investments. Simulations of the selected investments modelled in this analysis suggest that improvements in infiltration, decreases in surface runoff and decreases in erosion are achievable in the watershed. Further simulations suggest that a landscape-wide approach of terrace and bund construction has the greatest effect in terms of decreasing surface runoff, decreasing sediment yield and increasing groundwater flow and shallow aquifer recharge. A comprehensive landscape investment of terraces on slopes greater than 5% and bunds maintained on slopes less than 5% would decrease surface flow by almost 50%, increase groundwater flow by 15% and decrease sediment yield from erosion by 85%. However, constructing terraces in areas with greater than 5% slope (without constructing bunds in areas under 5% slopes) has a similar effect whereby surface flow and sediment yield decreases by 45 and 83%, respectively and groundwater flow increases by 13%. Residue management also has a significant effect on surface flow and erosion in the Mizewa watershed. Average annual surface flow decreased 17 when adopting residue management on all agricultural land and 26% when coupling terracing on steep slopes with residue management in mid-range slopes. These analyses provide the foundation for understanding feasible outcomes given a more comprehensive investment strategy. Results stemming from the current work can be paired with household level socio-economic data in order to assess program investment alternatives taking into account household constraints to Sustainable Land and Watershed Management (SLWM) investment and maintenance on private and public lands

Hydrological modelling of a catchment using the SWAT model in the upper Blue Nile basin of Ethiopia

Sustaining upland agriculture and food security is very much constrained by continuing land degradation brought by soil erosion due to lack of effective rainwater management strategies. Recently a large body of research evidence has established that significant potential exists to increase agricultural productivity through sustainable rainwater management interventions. Hydrological models are essential to understand the hydrological response of a catchment. The current paper focuses on hydrological modelling of catchment with SWAT model using its two versions, SWAT-CN and SWAT-WB. It is also aimed to verify the impact of existing land and water management practices on runoff yield and the applicability of the model for water resource assessment in the watershed. The model was applied on two watersheds, Mizewa (27 km2) and Gumara (1278 km2) that are located in the upper Blue Nile basin of Ethiopia in Fogera district. Data needed for modelling work was collected from available nearby stations and from the recently installed hydrological-meteorological stations. Model performances were compared prior to parameter optimization . After these initial findings, the SWAT-CN model was calibrated and validated and hence reasonable results were obtained. The results indicate that the model performance was in acceptable range and there are no many changes to predict the flow by the two versions of SWAT model. The concept of rainwater management is at an infant stage, though water scarcity and catchment degradation are serious threats in Mizewa watershed. HRU analysis indicates that agricultural land is the most runoff generating areas. Soil evaporation compensation factor (ESCO) and initial SCS curve number II value (CN2) are the two most sensitive parameters indicating that effective rainwater management interventions has a great impact in reducing soil erosion and land degradation. Some future management interventions were proposed such as discussing with local farmers and stakeholders

Mizewa watershed of the Blue Nile Basin

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Improving crop-livestock productivity and household income through the use of contour bunding and agroforestry options

A field study was carried out at Kani, Noupinesso, and Mpessoba in the Soudano-Sahelian zone of Mali to assess the impact of tillage, soil fertilization, and leguminous crops on runoff, soil erosion, soil moisture, and the growth and yield of cotton, sorghum, and fast-growing tree species. Experiments of 2 types were conducted. The treatments for the first trial consisted of 2 tillage practices (contour bunding (CB) and no contour bunding (NCB) which was the farmers’ practice) and 4 types of soil fertilization on cotton (control, organic manure, micro-dose, and recommended dose). The same trial was conducted on 6 different farms. The second trial consisted of 2 tillage practices (CB and NCB) and 3 cultural systems; (sorghum sole crop, soybean sole crop, and intercropped sorghum*soybean); the same trial was conducted on 9 different farms and in the Technology Park of Mpessoba. The experiment was laid out in a Split Plot with 4 replications. CB out-yielded NCB in all the measured parameters. The percentage of runoff coefficient in NCB plots was 34.89 - 38.79% and was decreased by CB to 17.46 - 21.48%. CB increased the water table dynamic at Noupinesso; the distance of groundwater to soil surface decreased to attain a minimum value of 2.61 m for the measuring tubes in the CB plot, 4.58 m in the NCB plot, and 1.02 m next to the outlet of the watershed. CB increased soil moisture in the horizon 0 - 100 cm at the 3 sites. The differences were high at the horizon 60-100 cm and at the end of the rainy season. The soil horizon (0 - 100 cm) under trees was slightly more humid than outside the trees in NCB, and the difference was higher in the CB plot. Organic manure increased cotton yield by 25.3% in Remon Sanou’s field, biomass yield by 29.66% in the field of Salif Berthe, cotton height and diameter by 72.36% and 34.54% in the trial of Barnabe Traore. The application of manure produced significantly (p < 0.05) less cotton growth and production than the applications of micro-dose (T3) and scale doses (T4). The T4 increased cotton yield by 144.79% and T3 by 130.21% in Bourama Dembele’s field, and biomass yield by 99.03% and 93.70% respectively in Sekou Berthe’s field. The use of CB technology significantly affected the growth and yields of cotton for all the 6 trials. in the field of Barnabe Traore cotton yield was higher by 42.5% in the CB plot compared to the NCB. Cotton height with CB increased by 29.30% in the trial of Bourama Dembele. Micro-dose treatment gave the best profitability as indicated by the VCR in the range of 4 to 8 for the 6 trials. Intercropping soybean and sorghum increased sorghum growth and yields for all the 9 trials. In some of the trials, yields of sorghum associated with soybean got more than twice the yields of sorghum cultivated alone. The trial of Youssouf Berthe give 1138 kg ha-1 grain yield with sole sorghum cultivation and 2325 kg ha-1 for the intercrop. The use of tillage methods affected sorghum and soybean growth and yields for all the 9 trials: the use of the CB method increased grain and biomass yield of sorghum and soybean by 50% and their height and diameter by 30%. The CB technology increased the growth of Gliricidia sepium and Leucaena leucocephala at the three research sites. Height (+35%), diameter (+25%), and crown radius (+40%) were increased in Gliricidia and in Leucaena by +58%, +69%, and +50% respectively. Key words: contour bunding, runoff and erosion, soil moisture, water table, micro-dose, intercropping, fodder plants

Runoff estimation and water management for the Holetta river in Ethiopia

The hydrology of Holetta River and its seasonal variability is not fully studied. In addition to this, due to scarcity of the available surface water and increase in water demand for irrigation, the major users of the river are facing a challenge to allocate the available water. Therefore, the aim of this research was to investigate the water availability of Holetta River and to study the water management in the catchment. Soil and Water Assessment Tool (SWAT) modelled the rainfall runoff process of the catchment. Statistical (coefficient of determination [R2], Nash- Sutcliffe Efficiency Coefficient [NSE] and Index of Volumetric Fit [IVF]) and graphical methods used to evaluate the performance of SWAT model. The result showed that R2, NSE and IVF were 0.85, 0.84 and 102.8, respectively for monthly calibration and 0.73, 0.67 and 108.9, respectively, for monthly validation. These indicated that SWAT model performed well for simulation of the hydrology of the watershed. After modelling the rainfall runoff relation and studying the availability of water at the Holetta River, the water demand of the area assessed. CropWat model and the survey analysis performed to calculate the water demand in the area. The total water demand of all three major users was 0.313, 0.583, 1.004, 0.873 and 0.341 MCM from January to May, respectively. The available river flow from January to May obtained from the result of SWAT simulation. The average flow was 0.749, 0.419, 0.829, 0.623 and 0.471 MCM from January to May respectively. From the five months, the demand and the supply showed a gap during February, March and April with 0.59 MCM. Therefore, in order to solve this problem alternative source of water supply should be studied and integrated water management system should be implemented