Remote Sensing and GIS-Based Soil Loss Estimation Using RUSLE in Bahir Dar Zuria District, Ethiopia

The severity of soil loss in the Ethiopian highlands has been increased from time to time. Hence, the assessment of soil erosion using models is very important for planning successful and sustainable soil management. This study was conducted in Bahir Dar Zuria district, Ethiopia with aiming to quantify the amount of soil loss using the GIS-based RUSLE (Revised Universal Soil Loss Equation) model. Based on the study, the most pronounced RUSLE factor that increases soil erosion was the slope length (L) and slope steepness (S). Compared with other land uses, bare land and cropland in the higher slopes were more vulnerable to erosion. As expected slope and soil losses have a direct relationship. About 80% of the study area experienced annual soil loss of less than 1.2 ton/ha/yr. Conversely, soil loss was very high for slopes greater than 30%. This indicated that slope has a great impact on regulating soil loss. The annual soil loss for cropland, vegetation, grassland, and degraded land was 19.05, 8.78, 8.82, and 71.16 ton/ha/yr., respectively. This is to means that land use land cover have a strong relationship with the amount of soil loss. The same land cover with different slopes have different soil loss amount. It was found that lack of vegetative cover during the critical period of rainfall, expansion of croplands, and absence of support practices increase soil erosion. Thus, the application of stone lines, contour tillage, terraces, and grass strip barriers are suggested to break the slope length into shorter distances, reducing overland flow velocity and soil erosion. Moreover, improving the awareness of society to reduce the illegal cutting of trees and apply conservation practices to reduce soil erosion in their farmland is very essential

Soil and irrigation water management : farmer’s practice, insight, and major constraints in Upper Blue Nile Basin, Ethiopia

This study assessed farmers’ soil and irrigation water management practices, perceptions, and major constraints at Koga, a large-scale irrigation scheme in Ethiopia. Key informant interviews, structured and semi-structured questionnaires, focus group discussions, and field visits were used for data collection. Soil samples were collected for the assessment of soil properties and a comparison with the respondents’ perception of soil-related constraints. A total of 385 respondents were involved in the questionnaire. All of the respondents had a good perception of soil acidity and its management strategies. Respondents’ perception was in line with the mean soil pH, soil texture, infiltration rate, exchangeable acidity, and soil organic carbon obtained from lab analysis and field tests. Soil acidity, unwise use of water, water scarcity, and lack of market linkages hampered the performance of the Koga irrigation scheme. Yet, respondents had a low awareness of irrigation water management. Farmers never used irrigation scheduling, but apply the same amount of water regardless of the crop type. As a result, low yield and water use efficiency were reported. To reduce soil acidity, an adequate lime supply for farmers with hands-on training on how to apply it would be desirable. Farmers should be aware of how to design effective irrigation scheduling and adopt water-saving management strategies

Wheat production and water productivity under deficit irrigation and integrated soil fertility management in Koga, Upper Blue Nile Basin, Ethiopia

Wheat is one of the staple crops in Ethiopia. Nationally, irrigated wheat production is done by resource-constrained smallholder farmers. But, in Koga, wheat productivity is declining from time to time owing to soil acidity-induced fertility problems coupled with water scarcity during the dry spell time. As a result of these factors, the soil's productive capacity has declined, and competition for scarce water has increased, resulting in lower wheat productivity despite increasing population demands for wheat production. This study was designed to explore the effects of deficit irrigation combined with improved soil management practices on wheat production and water productivity. A review of deficit irrigation and its effect on the water productivity of irrigated crops in Ethiopia was done. Besides, a detailed investigation of soil condition, irrigation water availability, irrigation project performance and major constraints that hampered irrigation development in Koga was done. Parallel to the baseline study, a detailed critical review of deficit irrigation's effect on water productivity, yield reduction and overall yield of irrigated crops was carried out. Based on the baseline study, fixed experimental plots were established at Ambomesk in the Koga irrigation scheme. Experiments were carried out under deficit and full irrigation for four consecutive irrigated seasons with two cropping intensities (2018/19 to 2019/20). Integrated soil fertility management (ISFM) treatments with three levels of lime, fixed level of manure and inorganic fertilizer were arranged in a randomized complete block design with three replications. The ISFM treatments were (i) 0.86 t ha-1 lime (60% of the lime requirement) combined with 3 t ha-1 manure and full dose inorganic fertilizer (L3), (ii) 1.15 t ha-1 lime (80% of lime requirement) combined with 3 t ha-1 manure and full dose inorganic fertilizer (L2), (iii) 1.43 t ha-1 lime (100% of lime requirement) combined with 3 t ha-1 manure and full dose inorganic fertilizer (L1), (iv) 3 t ha-1 manure combined with full dose inorganic fertilizers (M); and (v) full dose inorganic fertilizer (C) as a control. In the scenario analysis, we evaluated the effect of reducing the net irrigation requirement (100% ETc) by 50%, 40%, 20%, and 0% during the whole growth stages of wheat. The deficit irrigation (DI) strategies are expressed relative to the crop water requirements, ETc. The water application was done using a 15-cm throat width calibrated standard Parshall flume. The review results showed that DI considerably increased water productivity (WP) compared with full irrigation. Despite higher WP, the reduced yield was obtained in some of the studied DI practices compared to full irrigation. It was also found that yield reduction may be low compared to the benefits gained by diverting the saved water to irrigate extra arable land. Maize revealed the highest WP when irrigated at only the initial stage compared with being fully irrigated in all growth stages. Also, onion showed a decreasing WP with increased irrigation water from 60% crop water requirement (ETc) to 100% ETc. Increasing water deficit from 100 to 30% ETc led to an increase of wheat WP by 72%. For tomato, the highest WP was found at 75% ETc followed by 50% ETc and 85% ETc, while 100% ETc showed the least WP when DI was applied during the whole crop growing season. Teff showed the lowest WP under 25% ETc irrigation, while it was highest under 50% ETc and 75% ETc throughout the growing season. Teff is more susceptible to water stress when the crop water requirement is reduced by more than 50%. The baseline study confirmed that all of the respondents had a good perception of soil acidity and its management strategies. Respondents’ perception was in line with the mean soil pH, soil texture, infiltration rate, exchangeable acidity and soil organic carbon obtained from lab analysis and field tests. Soil acidity, unwise use of water, water scarcity and lack of market linkages hampered the performance of the Koga irrigation scheme. Over-fertilization-induced soil acidity problem hampers productivity and farmers' income in Koga. Yet, respondents had a low awareness of irrigation water management, which was confirmed by applying the same amount of water regardless of the crop type. As a result, low yield and water productivity were commonly found. Thus, to reduce soil acidity, an adequate lime supply for farmers with hands-on training on how to apply it would be desirable. Farmers should be aware of how to design effective irrigation scheduling and adopt water-saving management strategies. Our findings show significantly higher (P L2 > M > L3 > and C for both soil depths 0-10 and 10-20 cm. The Ks under plots treated with L1 was 64% and 37% higher than that of C for the 0-10 and 10-20 cm soil depths, respectively. Significantly (P<0.05) higher infiltration capacity was found at L1 followed by L2, L3 and M compared with C. Good soil structural quality (Sq) score was identified in L1, L2, L3 and M, whereas in C poor Sq score was found. In conclusion, the application of organic manure combined with lime and inorganic fertilizer enhanced the infiltration rate and water holding capacity more than the inorganic fertilizer application alone. The effect of DI and liming, as well as manuring on average grain yield and biomass, were highly significant. Under all irrigation scenarios, higher grain yield and biomass were found at L1, L2, L3 and M, compared with C. The highest WP was obtained at 50% ETc at L1, L2, L3 and M, respectively, compared with 100%, 80% and 60% ETc. Yet, the lowest WP was found at C under all irrigation scenarios compared with L1, L2, L3 and M. The WP increased when the amount of water supply decreased and liming doses increased. Under 100%, 80% and 50% ETc irrigation scenarios, full dose liming is more profitable but, at 60% ETc, manuring is more profitable. Profitability rises as irrigation water supply reduces. It could be concluded that liming and manuring could be used to mitigate the yield penalty effect of DI. In conclusion, the findings of this study demonstrate that to increase wheat production in Koga, deficit irrigation and enhanced soil management strategies are required. From a soil management viewpoint, farmers are advised to practice liming and manuring combined with inorganic fertilizers to boost soil quality which in turn, enhances wheat production and water productivity. From an irrigation water management standpoint, farmers can apply 60% ETc to save more water to irrigate extra land with less yield penalty

Implications of land management practices on selected ecosystem services in the agricultural landscapes of Ethiopia : a review

Human-induced land degradation and impairment of ecosystem services (ES) are among the serious problems in Ethiopia due to excessive pressure on land and water resources. Thus, various land management (LM) practices have been done to enhance ES and environmental sustainability. However, very little is known about the influence of efficacious LM practices on multiple ES. This study aims at assessing the implication of LM practices on crop yield, soil carbon stock, soil fertility, soil moisture, runoff, soil loss, nutrient loss, and cultural/societal services. A systematic review and synthesis methods were employed. Predefined criteria were used to screen relevant articles; thereby, 572 observations from 94 studies were extracted and synthesized. The results showed that agronomic practices increased grain yields, soil carbon stock, soil fertility, and soil moisture on average by 28, 29, 43 and 14%, respectively. Biological practices regulated runoff, soil loss, and nutrient loss on average by 46, 59 and 94%, respectively. Overall, LM practices were efficacious to enhance delivery of ES bundles but soil bund and fanyaa juu reduced the grain yield on average by 24 and 22%, respectively. This indicates that there are trade-offs between provisioning and other services like regulating, supporting and cultural under physical structures. However, landscape-level collective impact of different LM practices exhibited without any ES trade-offs. The integration of properly designed physical structures with agronomic and biological practices is imperative to enhance ES and balance the trade-offs in the agricultural landscapes. Further, it is important to find out alternative combinations of agricultural LM practices and evaluate for ES delivery

Comparative analysis of groundwater conditions on rain-fed and irrigated agriculture in the upper Blue Nile basin, Ethiopia

Study region: Upper Blue Nile Basin, Ethiopia. Study focus: This study was conducted at the Koga Irrigation Scheme in the upper Blue Nile basin (Ethiopia) to investigate the influence of irrigation activity on the groundwater system. Representative samples of six shallow wells in the irrigated fields and four shallow wells in the adjacent non-irrigated (rain-fed agricultural lands) were selected. Dipmeter and hand GPS (GARMIN 60) were used for the monitoring of water table depth and fixing the location of the wells respectively. Arc GIS 10.5 has been applied for interpolation of water table depth (WTD). Water samples were collected and analyzed in the laboratory following international standards. New hydrological insights for the region: The result shows that irrigation contributed to the water table rises of wells located in the irrigated fields which range from 0.77 m to 0.52 m and water table drops were observed in wells located in the non-irrigated fields. Investigations on the groundwater quality (GWQ) indicated that no significant effect was observed in the irrigated and non-irrigated fields. The study shows that good irrigation water management, continuous follow-up of the groundwater table and its physico-chemical properties are essential for the sustainability of the Koga Irrigation Scheme

Deficit irrigation as a sustainable option for improving water productivity in Sub-Saharan Africa : the case of Ethiopia : a critical review

Improving irrigation water management and enhancing water productivity (WP) is required to address future water scarcity in the sub-Saharan region. Maximizing WP by exposing the crop to a certain level of water stress using deficit irrigation (DI) is considered a promising strategy. To adopt DI strategies, a shred of comprehensive evidence concerning DI for different crops is required. This review aims to provide adequate information about the effect of DI on WP. The result showed that DI considerably increased WP compared to full irrigation. Despite higher WP, the reduced yield was obtained in some of the studied DI practices compared to full irrigation. It was also found that yield reduction may be low compared to the benefits gained by diverting the saved water to irrigate extra arable land. Maize revealed the highest (2.7 kg m(-3)) and lowest (0.5 kg m(-3)) WP when irrigated at only the initial stage compared with being fully irrigated in all growth stages. Also, onion showed a decreasing WP with increased irrigation water from 60% crop water requirement (ETc) (1.8 kg m(-3)) to 100% ETc (1.3 kg m(-3)). Increasing water deficit from 100 to 30% ETc led to an increase of wheat WP by 72%. For tomato, the highest WP (7.0 kg m(-3)) was found at 70% ETc followed by 50% ETc (7.0 kg m(-3)) and 85% ETc (6.9 kg m(-3)), while 100% ETc showed the least WP (6.8 kg m(-3)). Teff showed the lowest WP (1.7 kg m(-3)) under optimal irrigation, while it was highest (3.0 kg m(-3)) under 75% ETc throughout the growing season. The regression analysis for WP increment and yield reduction versus saved water showed higher values, indicating that DI could be an option for WP increment and increasing overall yield by expanding irrigated area and applying the saved water in water-scarce regions

Effect of deficit irrigation and soil fertility management on wheat production and water productivity in the Upper Blue Nile Basin, Ethiopia

In the Ethiopian Upper Blue Nile Basin, like in other regions in the world, agricultural productivity is declining due to water scarcity owing to longer dry seasons coupled with soil acidity-induced fertility problems. Wheat is one of the major food security crops in Ethiopia but its productivity is reduced due to water scarcity, especially during the irrigation season. Addressing these problems might be essential to increase productivity. This study explores the effect of deficit irrigation (DI) combined with lime, manure and inorganic fertilizer on wheat production and water productivity (WP) in the Koga irrigation scheme, Ethiopia. Four levels of DI strategies (100% ETc or 0% deficit as a control, 80%, 60% and 50% ETc) were applied for two irrigated seasons. Five levels of soil fertility management were applied for four consecutive cropping seasons: (i) 0.86 t ha- 1 lime combined with 3 t ha- 1 manure and full dose urea and NPS-B (hereafter referred to as inorganic fertilizer) (L3); (ii) 1.15 t ha- 1 lime combined with 3 t ha- 1 manure and full-dose inorganic fertilizer (L2); (iii) 1.43 t ha- 1 lime combined with 3 t ha- 1 manure and full dose inorganic fertilizer (L1); (iv) 3 t ha- 1 manure combined with full dose inorganic fertilizer (M); and (v) full dose inorganic fertilizer alone (C). The grain yield and biomass data were collected at harvest from a sample area of 2 m x 3 m from each plot with three replicates. The effect of DI and liming, as well as manuring on average grain yield and biomass, were highly significant. Under all irrigation scenarios, higher grain yield and biomass were found at L1, L2, L3 and M (in that order), compared with C. The highest WP was obtained at 50% ETc irrigation dose, compared with 60%, 80% and 100% ETc (in that order). Yet, the lowest WP was found at C under all irrigation scenarios compared with L1, L2, L3 and M. The WP increased when the amount of water supply decreased and liming doses increased. The application of full dose lime and manure combined with 50% ETc DI resulted in comparable grain yield, biomass and WP as 100% ETc full irrigation at L3 and M. It could be concluded that liming and manuring could be used to mitigate the yield penalty effect of DI in the study area. In scenarios where farmers have to pay for water, profitability rises as the irrigation water supply reduces. Thus, under such conditions, a 50% ETc irrigation scenario is more profitable than scenarios with 60%, 80% and 100% ETc irrigation

Effect of integrated soil fertility management on hydrophysical soil properties and irrigated wheat production in the upper Blue Nile Basin, Ethiopia

In Ethiopia, soil fertility problem caused by acidity substantially limits agricultural productivity, necessitating sustainable integrated nutrient management. This study assessed the effect of combined application of lime, manure and inorganic fertilizer on selected hydrophysical properties of an acid clay Nitisols in the Koga irrigation scheme, Ethiopia. Five levels of integrated soil fertility management treatments were tested for four consecutive cropping seasons: (i) 0.86 t ha(-1) lime combined with 3 t ha(-1) manure and full-dose inorganic (urea and NPS-B) fertilizer (L3); (ii) 1.15 t ha(-1) lime combined with 3 t ha(-1) manure and full-dose inorganic fertilizer (L2); (iii) 1.43 t ha(-1) lime combined with 3 t ha(-1) manure and full-dose inorganic fertilizer (L1); (iv) 3 t ha(-1) manure combined with full-dose inorganic fertilizer (M); and (v) full-dose inorganic fertilizer alone (C) as a control. Undisturbed soil samples were collected at 0-10 and 10-20 cm soil depths and analyzed to determine saturated hydraulic conductivity (Ks), soil-water retention characteristics, total porosity and bulk density. Disturbed soil samples were collected at the same depths to analyze soil organic carbon and texture. Infiltration capacity measurements and visual evaluation of soil structural quality were done in the field. Significantly higher (P L2 > M > L3 > and C for both soil depths 0-10 and 10-20 cm. The Ks under plots treated with L1 was 64% and 37% higher than that of C for the 0-10 and 10-20 soil depths, respectively. Significantly (P < 0.05) higher infiltration capacity was found at L1 (0.007 cm min(-1)) followed by L2, L3 and M (0.006 cm min(-1), 0.006 cm min(-1), and 0.005 cm min(-1)) compared with C (0.004 cm min(-1)), respectively. Good soil structural quality (Sq) score was identified in L1, L2, L3 and M, whereas in C poor Sq score was found. As compared with C, grain yield was improved by 69% at L1, 59% at L2, 53% at L3, and 44% at M during 2018 and by 70% at L1, 58% at L2, 55% at L3 and 46% at M in 2019. In conclusion, the application of organic manure combined with lime and inorganic fertilizer enhanced the infiltration rate, water holding capacity and grain yield more than the inorganic fertilizer application alone. There was also a significant effect of liming as such, with the highest doses showing the best results