The nitrogen fertilizer replacement values of incorporated legumes residue to wheat on vertisols of the Ethiopian highlands.

Soil fertility depletion and continuous cereal cropping are reducing crop production in Ethiopia. Integrated Soil Fertility Management (ISFM) is a good approach for resource-poor farmers because ISFM can help reduce the need for inorganic fertilizer by increasing nitrogen (N) availability in the soil. The study aimed to investigate the effect of preceding crops, legume residue management practices, and N levels on wheat planted. The experiment was set up using a split plot in a randomized complete block design with three replications. The N fertilizer replacement value method was used to estimate the N contribution of legumes to a succeeding wheat crop. The results showed that grain yield and N uptake of wheat crops varied in response to N fertilizer, legume residue management treatments, and tillage practices. Legume residue incorporation positively influenced the agronomic parameters of wheat compared to teff and fallow wheat rotations. The average N fertilizer replacement value from legume rotation was 18-46 kg ha-1. This study showed that a one-year legume-in-biannual wheat rotation is preferable to lying bare fallow during the cropping season. Nevertheless, drainage during legume and wheat cropping is a condition for providing full positive impacts.

Effects of land-use-cover-changes on selected soil physicochemical properties along slope position, Coka watershed, Southern Ethiopia.

Land-use changes along slope position can have a major positive or negative impact on soil environment and agricultural productivity. Relevant information to understand the negative effect of land-use change and slope variability on soil property is a vital element to monitor, plan and make the decision to improve productivity and restore the environment. The aim was to examine the effects of land-use-cover-changes along slope position on the selected soil physicochemical properties in the Coka watershed. Soil samples were gathered from 5 nearby land uses, namely forestland, grassland, bushland, cultivated land, and bare-land, and 3 slope positions (upper, middle, and lower slope) at 0-30 cm soil-depth, analyzed in Hawassa University Soil testing laboratory. The results show that the highest field capacity, available water-holding, porosity, silt, nitrogen, pH-value, cation exchange capacity, sodium, magnesium, and calcium were in forestlands and lower-slope. The highest water-permanent-wilting-point, organic-carbon, soil-organic-matter, and potassium were in bushland; bulk density was in bare land while the highest clay and available-phosphorus were revealed in cultivated land and lower slope. Most soil properties showed a positive correlation with each other except bulk density which has a negative correlation with all soil properties. Generally, cultivated land and bare land have the least concentration in most soil properties which indicates of increasing degradation rate in the area. Thus, soil-organic-matter and other yield-limiting nutrients should be improved in cultivated land to maximize productivity by using an integrated implementation of soil fertility management through cover crops and rotation, compost, manures, and minimum tillage; and amending soil pH-value by liming.

Effect of lime rates and method of application on soil properties of acidic Luvisols and wheat (Triticum aestivum, L.) yields in northwest Ethiopia.

Soil acidity has become a major constraint that threatens sustainable agricultural production in Ethiopia. This study was conducted to evaluate effects of lime rates and application methods on selected soil properties and wheat (Triticum aestivum, L.) yields on acidic Luvisols of northwestern Ethiopia. The treatments included control, 0.5, 1, 2 and 3 t ha-1 lime drilled along the seed rows and 2, 3, 6 and 12 t ha-1 lime applied in broadcasting method. The experiment was arranged in a randomized complete block design (RCBD) with three replications. Lime rates applied for this experiment were quantified using exchangeable acidity and Buffer pH methods. To analyze selected soil properties, composite soil samples were collected immediately before sowing and after harvest. Results revealed that liming significantly increased soil pH, available phosphorus, and exchangeable bases but markedly reduced exchangeable Al3+ contents. The lime rates determined by buffer pH method were greater in ameliorating soil acidity, increasing soil nutrients status and crop yields than exchangeable acidity. Besides, lime application along the row was better in overcoming soil acidity constraints and increasing crop yields compared to broadcast application. Application of 12 t ha-1 lime in the broadcasting method, 3 t ha-1 and 2 t ha-1 lime drilling along the row increased wheat grain yield by 65.10, 49.80 and 27.05%, respectively, compared to the control. Likewise, partial budget analysis showed that the highest net benefit (51,537 Birr ha-1) was obtained from plots amended with 3 t ha-1 lime while the lowest economic profit (31,627.5 Birr ha-1) was recorded from treatments that received 12 t ha-1 lime. Thus, we concluded that application of 3 t ha-1 lime in row is a promising practice to mitigate soil acidity and increase available nutrients, exchangeable bases and crop yields in the study area and similar soil types elsewhere.

Spatiotemporal dynamics of soil loss and sediment export in Upper Bilate River Catchment (UBRC), Central Rift Valley of Ethiopia.

Soil loss is one of the major challenges for agricultural production in the Ethiopian highlands. The rate and distribution of soil loss (SL) and sediment export (SE) are essential to map degradation "hotspot" areas for prioritizing soil and water conservation measures. The objective of this study was to estimate the dynamics of SL and SE in the Upper Bilate River Catchment of Central Ethiopia. The Sediment Delivery Ratio (SDR) module of the Integrated Valuation of Ecosystem Services and Trade-offs (InVEST) model was used to estimate and map SL and SE. The primary input data were rainfall, soil data, land use, and other biophysical parameters of the study area. The model output confirmed that the average total soil loss of the catchment was 36.8 million ton/yr. It is modeled that soil loss doubles within 30 years. The average annual sediment export was about 3.62 ton/ha/yr. The mean annual soil loss of the study area was 23 ton/ha/yr, which exceeded the soil loss tolerance (SLT), estimated to range between (2-18 ton/ha/yr) in Ethiopia. Based on the soil erosion risk level, about 22% of the catchment area was classified as severely degraded, while 62 % was moderately degraded. Severe soil erosion prevails in the sub-watershed (SW)-5, SW-4, and SW-13. Therefore, these sub-watersheds need priority conservation action to restore the ecosystem processes of the study area.

Soil organic carbon and its' stock potential in different land-use types along slope position in Coka watershed, Southern Ethiopia.

Understanding organic carbon accumulations in soils is crucially essential concerning carbon sequestration, fighting climate change, increasing land productivity, improving soil properties, providing energy to the microbial community, enhancing ecological restoration, and reversing global environmental damage. This study was aimed at assessing the effects of land-use-cover change (LULC) on soil organic carbon (SOC), its' stock potential, and bulk-density (BD) along slope position in the Coka watershed. Replicated soil samples had been collected and composited from 30 cm depth topsoil of five major land use types and three slope positions. This result showed that significantly (P < 0.001) lowest and highest mean of soil organic carbon stock (SOCS) was observed under bare lands (37.835 Mg ha-1) and bushlands (144.582 Mg ha-1), respectively which was the same for SOC concentration. Barelands lose 3.82 times (3.82x) higher SOCS than bushland and 2.68x more SOCS than forestland. Both SOC-stock and SOC showed significant (P < 0.001) differences among slope positions, which were the highest in lower-slope followed by middle-slope, which had 1.8 and 2.6x higher than in middle-slope and upper-slope positions, respectively. Thus, the multivariate-test result divulges that LULC along slope positions has a strongly significant (P < 0.05) main and interaction effect on SOCS in the area. Therefore, the potential contribution of bushland and forestland uses should be improved for SOC sequestration, soil productivity improvement, and environmental protection.

Effects of habitat gradient and agro-climatic variation on selected soil physical and chemical properties in the Bale Mountains national park, south-eastern Ethiopia.

BACKGROUND: Increasing evidence suggests that anthropogenic effects are responsible for drastic changes in landscape patterns and ecosystem services. This study aims to assess the effects of landscape change and agro-climatic variation on selected soil physical and chemical properties in the Bale Mountains national park. A combination of stratified and systematic sampling techniques was employed to draw representative soil samples. A total of 72 soil samples (3 agro-climatic zones × 3 land cover types × 2 habitat gradients × 4 replications = 72) at a depth of 0-20 cm were collected for the soil physical and chemical property analysis. A two-way analysis of variance was conducted to determine the level of variation in soil parameters. Tukey's honest significance difference (HSD) test was used to compare treatment means at a 0.05 level of significance. RESULTS: The results suggest that soil parameters differed significantly (p < 0.05) among agro-climatic zones, land cover, and habitat gradients. The soil pH, SOC, TN, AP, CEC and clay content were significantly higher in the lower altitude, natural vegetation and interior habitat, whereas the soil sand and silt content as well as the soil bulk density were significantly higher in the farmland and edge habitat. CONCLUSIONS: Conservation and restoration priority should be given to those vegetation types and ecosystems that are highly affected by human interferences such as the grassland in the middle altitude, ericaceous land in the higher altitude, and moist forest in the lower altitudes.

Soil type and fertilizer rate affect wheat (Triticum aestivum L.) yield, quality and nutrient use efficiency in Ayiba, northern Ethiopia.

The blanket NP fertilizer recommendation over the past five decades in Ethiopia did not result in a significant increment of crop productivity. The main lack of success was highly linked to the extrapolating approach of one site success to others without considering the climate, soil, and ecological setting and variations. As a result, a new fertilization approach was desperately needed, and with this premise, new blended fertilizers are now being introduced to replace the conventional approach. Thus, the objective of this study was to examine the effect of NPSZnB blended fertilizer on bread wheat yield attributes, quality traits and use efficiency in two different soil types under rain-fed conditions in Ayiba, northern Ethiopia. Relevant agronomic data were evaluated and recorded from plots of each soil types for analysis. The analysis of variance revealed a significant (p < 0.001) variation on all the agronomic and grain quality traits due to the main and interaction effects of soil type and fertilizer treatment factors. Most agronomic and quality characteristics recorded the highest result in the highest treatment applications (175 and 150 kg NPSZnB ha-1) in both soils. Yield and grain quality traits of bread wheat was also found better under fertilized plots than unfertilized plots. In both soil types increasing application of the new blended fertilizer rate from 50-175 kg NPSZnB ha-1 showed an increasing trend in grain yield from 1.6 to 4.3 and 2.5 to 5.4 t ha-1 in Vertisol and Cambisol soils, respectively. The varied yield as a response of fertilizer treatments across soils signifies soil-specific fertilization approach is critically important for production increment. On the other hand, based on the partial budget analysis the highest net benefit with the highest marginal rate of return in both Vertisol and Cambisol soils were obtained when treated with 100 and 125 kg NPSZnB ha-1, respectively. Therefore, to produce optimum bread wheat yield under rainfed conditions in Ayiba (northern Ethiopia) fertilizing Vertisols with 100 kg NPSZnB ha-1 and fertilizing Cambisols with 125 kg NPSZnB ha-1 is recommended.

Expressing carbon storage in economic terms: The case of the upper Omo Gibe Basin in Ethiopia.

Terrestrial carbon storage is important for planning decisions regarding climate change. Therefore, modelling the spatial distribution of carbon storage and valuation can help restore the sustainability of the ecosystems. This study aimed at showing the spatial and temporal variations in carbon storage and valuation in the upper Omo Gibe Basin. Land use/cover and carbon pool data based on field data collection and laboratory analyses supported by GIS and remote sensing were used. The Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) software was used for modelling carbon storage. The Global voluntary carbon market price and Tropical Economics of Ecosystems and Biodiversity (TEEB) data were used for describing carbon storage in economic terms. ANOVA was carried out to detect significant differences in carbon stock correlation with parameters. The results show that the annual carbon stock declined by 0.37 t/ha and the carbon market declined from USD 25.04 billion in 1988 to USD 24.01 billion in 2018. The highest loss of carbon storage and valuation was found in forest land followed by grazing land. Moreover, carbon stock was positively correlated with NDVI and habitat quality (p < 0.05). Slopes did not affect carbon stock (p > 0.05). This study helps promote and enhance carbon trading.

Evaluation of Water Provision Ecosystem Services Associated with Land Use/Cover and Climate Variability in the Winike Watershed, Omo Gibe Basin of Ethiopia.

The provision of freshwater is essential for sustaining human life. Understanding the water provision modelling associated with the Land Use/Cover (LUC) change and climatic factors is vital for landscape water resource management. The Winike watershed is the largest tributary in the upper Omo Gibe basin of Ethiopia. This research aims to analyze the spatial and temporal change in the water yield to investigate the water yield contribution from the watershed based on the variation in input parameters. The Integrated Valuation of Ecosystem Services and Tradeoffs Tool (InVEST) water yield model was used to evaluate the spatial and temporal variation of the water yield in different years (1988, 1998, 2008 and 2018). The data required for this model include LUC data from satellite images, reference evapotranspiration, root depth, plant available water, precipitation, season factor (Z), and a biophysical table. The analysis of LUC change shows a rapid conversion of grazing land, shrubland, and forest land into cultivated land. There has been a significant variation in water provision, which increased from 1.83 × 109 m3 in 1988 to 3.35 × 109 m3 in 2018. Sub-watersheds 31, 32, and 39 in the eastern part of the watershed contributed more water due to higher precipitation and lower reference evapotranspiration. The major increase in the contribution of water yield was in built-up land by 207.4%, followed by bare land, 148.54%, and forest land by 63%. Precipitation had a greater impact on water yield estimation compared with the other input parameters. Hence, this research helps decision-makers to make informed decisions regarding new policies for LUC change improvement to maintain the water resources in the Winike watershed.

Dry matter production, nitrogen yield and estimation of nitrogen fixation of legumes on vertisols of the Ethiopian highlands.

Traditional land management techniques on vertisols frequently lead to soil fertility loss and land degradation. The objective of this study was to evaluate the impact of improved land preparation methods on the dry biomass and nitrogen (N) content of two legume species grown under two phosphorus fertilizer applications. The experimental design employed for these experiments was a randomized complete block design, with six treatments and four replications. Land preparation methods and phosphorus application significantly (P < 0.05) increased biomass production and N content in legumes. Over years and land preparation methods, vetch N accumulation was superior (P < 0.05) to clover and teff (Eragrostis teff). Such a large amount of N accumulation may have a positive contribution to subsequent crops when incorporated into the soil. Land preparation methods and years influenced soil mineral N accumulation, particularly under legumes. The N balance values indicated that it differed among species, land preparation methods, and P treatments over the year. The N balance of vetch +P ranged from 67.1 to 185.9 kg N ha-1 over years and land preparation methods, whereas the comparable figure for vetch-P was 40.3-141.9 kg N ha-1. Similarly, the N balance in clover-P ranged from 13.0 to 67.2 kg N ha-1, and in clover +P from 13.8 to 98.6 kg N ha-1. Teff's N balance has never exceeded 35 kg ha-1 over the years.

Allometric equations for selected Acacia species (Vachellia and Senegalia genera) of Ethiopia.

BACKGROUND: Allometric equations are used to estimate biomass and carbon stock of forests. In Ethiopia, despite the presence of large floral diversity, only a few site-specific allometric equations have been developed so far. This study was conducted in the Omo-Gibe woodland of south-western Ethiopia to develop an allometric equation to estimate the Above-ground Biomass (AGB) of the four Acacia species (Senegalia polyacantha, Vachellia seyal, Vachellia etbaica and Vachellia tortilis). Fifty-four (54) Acacia trees were sampled and measured within 35 temporarily established square plots. In each plot, dendrometric variables were measured to derive the models based on combinations of Diameter at Breast Height (DBH), height, and wood density as predictor variables. Model performance was evaluated using goodness-of-fit statistics. The biomass was compared using four allometric biomass models that have been widely used in the tropics. RESULTS: The model containing DBH alone was more accurate to estimate AGB compared to the use of multiple predictor variables. This study, therefore, substantiated the importance of site-specific allometric equations in estimating the AGB of Acacia woodlands. This is because a site-specific allometric equation recognizes the environmental factors, vegetation types and management practices. CONCLUSIONS: The results of this study contribute to a better understanding of allometric equations and an accurate estimate of AGB of Acacia woodlands in Ethiopia and similar ecosystems elsewhere.

Characterization and classification of soils of Bako Tibe District, West Shewa, Ethiopia.

The study was carried out at Bako Tibe District, West Shewa zone, Oromiya Region of Ethiopia, to characterize and classify agriculturally important acidic soils. Four soil types were considered and six representative pedons were opened and a total of 27 disturbed and 20 core ring soil samples were collected from identified horizons of each pedon and analyzed. The field and laboratory data revealed the soils were clay and sandy clay in texture, slightly acidic to strongly acidic in reaction (pH 5.2-6.63). The organic carbon content of the soil ranges between moderate 21.4 g kg-1 to high 30 g kg-1 for surface soil while very low (4 g kg-1) to high (26 g kg-1) for sub-surface soils. Both the surface and subsurface soils were very low (1.7-2.2 g kg-1) in total N and deficient (5.99-7.85 mg kg-1) in available P content. The cation exchange capacity (CEC) was high for all surface and sub-surface percent base saturation was low (25 cmol (+)kg-1) for Alisols and medium for Nitisols, Luvisols, and Cambisols (51 and 50 cmol(+)kg-1). The soils were sufficient in available Fe, Mn, and Zn but deficient in B and Cu. Pedon-1 was Dystric, Rhodic Nitisols (Humic); pedon-2, Dystric Nitisols (Humic); pedon-3, Umbric Nitisols; pedon-4, Rhodic Alisols (Hyperdystric); pedon-5, Rhodic Luvisols (Hypereutric); pedon-6, Leptic Cambisols (Humic). Soil characterization is helpful to use the land according to its capability and limitations. pedons 2 and 4 were categorized under LCC IIs. pedons 1, 3, and 5 were grouped within LCC IIIes while Pedon 6 was grouped under LCC IVes. All the soil profiles studied can be used for crop production with appropriate management practices. Different agronomic and physical soil and water conservation measures such as cover crops, counter farming, graded bands, and lime application are some of the corrective measures for the limitations.

Class and landscape level habitat fragmentation analysis in the Bale mountains national park, southeastern Ethiopia.

The changes of natural habitat structure and function due to human interference is hastening worldwide, and it is compulsory to preserve biological resources in a protected system. This study aims to measure the landscape ecological structure and the extent of habitat fragmentation in the Bale mountains national park. The land use/land cover change was determined by interpreting the 1985, 1995, 2005 and 2017 Landsat images with ArcGIS 10.3, and the selected landscape structural metrics was analyzed using FRAGSTATS 4.2.1. All land cover classes showed a declining trend, except the farmland, and grassland depicted the highest area reduction. From 1985 to 2017 grassland, Erica, forestland, and afro-alpine were decreased by 9.36 %, 0.26 %, 0.06 %, and 0.01 %, respectively. Whereas, farmland was increased by 43.67 %. The study area was characterized as progressively fragmented since it was signified by the escalated value of patch number (40.22 %), area-weighted mean shape index (18.84 %), and edge density (22.27 %) and a declined value of mean patch size (28.68 %) and core area (10.60 %) over the study period. Considering this result, there was a high loss in area available for core dependent species, particularly for Mountain nyala in the grasslands and woodlands, Ethiopian wolf in afro-alpine regions, and Bale monkey in the bamboo forest. Both forestland and grassland need a conservation priority since these habitats were the most fragmented and habitat lost area.

Impact of land use type and altitudinal gradient on topsoil organic carbon and nitrogen stocks in the semi-arid watershed of northern Ethiopia.

Understanding the role of soils in the soil organic carbon (SOC) and total nitrogen (TN) cycle is essential, assumed that these parameters are among the key soil quality indicators in a given landscape. Nothing but their status is in a state of continual flux due to land-use, soil management practices, and nature of topographic features. Thus, this study has evaluated the effect of land-use types and altitudinal gradient on SOC and TN concentrations and stocks at a watershed scale in northern Ethiopia. A total of 450 topsoil samples (0-30 cm depth) were collected from four different land-use types (Fig.3) across three elevational categories (Fig.1(b)), and their SOC and TN distributions were studied using descriptive statistics and geostatistical methods. Results revealed significant (p < 0.05) differences in SOC and TN concentrations and stocks by land-use type, elevation, and their interactions. The highest SOC stock was recorded at the lower elevation in GL (7.24 Mg C ha-1), followed by PF (4.65 Mg C ha-1) in the middle and GL (4.61 Mg C ha-1) in the upper elevations, respectively. On the other hand, the lowest SOC stock was observed in the BL areas of the upper (2.34 Mg C ha-1) and middle (2.75 Mg C ha-1) elevations. Spatially, the mean SOC stocks of the different land-uses were in the following order: GL > PF > CL > BL in upper elevation, PF > GL > CL > BL in middle elevation, and GL˃CL in lower elevation, respectively. The estimated total SOC and TN stocks of the study watershed were about 46,868.66 ± 7747.38 Mg C and 7,008.02 ± 441.25 Mg N, respectively. The notable difference is attributable to lack of vegetation cover, unsustainable land-use system, and land degradation via water erosion. Hence, these physical landscape disturbances result in disruption of SOC and TN's storage and stability. The SOC and TN stocks have shown a significant (p < 0.05) negative correlation with soil bulk density in the study watershed. The study concludes that variations in the land-use along topographic gradients drive the soils' SOC and TN storage. Therefore, land suitability planning, soil and water conservation measures, and reforestation practices are needed and practical worth increasing SOC and TN storage in the watershed.

Land Use/Land Cover Change and Its Driving Forces in Shenkolla Watershed, South Central Ethiopia.

Land use change is one of the challenges that aggravate environmental problems. Understanding the scope of land use change, driving forces, and consequences is very crucial for proper management of land resources. We investigated land use/land cover changes using remote sensing data (for the years 1973, 1995, and 2017), and field observation, household survey, key informant interview, and focus group discussion were used to determine the drivers and consequences of land use/land cover changes in Shenkolla watershed, south central Ethiopia. Unsupervised and supervised classification techniques were employed to get thematic information from satellite imagery. ArcGIS 10.3 and QGIS v 3.0 softwares were used to accomplish the analysis. The results disclosed that Shenkolla watershed has changed significantly during the past 4 decades between 1973 and 2017. This observed change indicates a reduction in forest land and an increase in agricultural land. Forest land was reduced from 29.51% in 1973 to 20.52% in 2017, but agricultural land was expanded from 70.49% in 1973 to 79.48% in 2017. Agricultural expansion, policy change and social unrest, population pressure, shortage of farm land, and biophysical factors were major driving forces of the LU/LC changes. Environmental implications such as climate change, biodiversity loss, scarcity of basic forest products, habitat alteration, decline in quality and availability of water, and crop yield reduction are the consequences of the LU/LC change. The expansion of agricultural land at the expense of forest cover in Shenkolla watershed has negative implications on the natural resources and the livelihood of local people. Hence, appropriate measures need to be employed to reduce the dramatic change in land use and to harmonize environmental conservation with human livelihood.

Integrated fertilizer application improves soil properties and maize (Zea mays L.) yield on Nitisols in Northwestern Ethiopia.

Soil fertility depletion is emerging as a serious challenge causing low crop yields and food insecurity in Ethiopia. An on-farm experiment was conducted in 2017/2018 cropping season to investigate the effects of combined application of compost and mineral fertilizer on selected soil properties and maize yield in North-western Ethiopia. Treatments were factorial combinations of three rates of Urea/NPSB (0/0, 50/50 and 100/100 kg ha-1) and three rates of compost (0, 5 and 10 t ha-1). The field experiment was arranged in randomized complete block design (RCBD) with three replications. Results showed that combined application of compost and mineral fertilizer significantly (p < 0.05) increased soil pH, organic carbon (OC), total nitrogen (TN), available phosphorus (AP), available sulphur (AS) and cation exchange capacity (CEC) compared to sole mineral fertilizer application and the control. On the other hand, there was significant (p < 0.01) decrease in soil bulk density. Plots amended with 10 t ha-1 compost and 100/100 kg ha-1 Urea/NPSB provided the highest maize dry biomass (18.62 t ha-1) and grain yield (6.07 t ha-1). Conversely, the lowest biomass (5.70 t ha-1) and grain (1.17 t ha-1) yields were obtained from the control. The partial budget analysis also showed that the highest net benefit (32700 Birr ha-1) was obtained from combined addition of organic and mineral fertilizer which was significantly higher than applying the highest rate of sole mineral fertilizer (27438 Birr ha-1), highest rate of sole compost (9011.3 Birr ha-1) and the control (7660 Birr ha-1). Therefore, we concluded that integrated fertilizer management improves soil properties and crop yield in the highlands of north-western Ethiopia.

Land use/land cover change effect on soil erosion and sediment delivery in the Winike watershed, Omo Gibe Basin, Ethiopia.

Information on soil loss and sediment export is essential to identify hotspots of soil erosion to inform conservation interventions in a given watershed. This study investigates the dynamics of soil loss and sediment export associated with land-use/land cover changes and identifying soil loss hotspot areas in the Winike watershed of the Omo-Gibe Basin of Ethiopia. Spatial data collected from satellite images, topographic maps, meteorological and soil data were analyzed. The land-use types in the study area were categorized into six: cultivated land, woodland, forest, grazing, shrubland, and bare land. The Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) of the sediment delivery ratio (SDR) model was used based on the analysis of land use/land cover and RUSLE factors. The results show that total soil loss increased from 774.86 thousand tons in 1988 to 951.21 thousand tons in 2018 while the corresponding sediment export increased by 3.85 thousand tons for the same period. These were subsequently investigated in each land-use type. Cultivated fields generated the highest soil erosion rate, increasing from 10.02 t/ha/year in 1988 to 43.48 t/ha/year in 2018 when compared with the grazing, shrub, forest, wood land and bare land-use types. This corresponds with the expansion of the cultivated area. This is logical as the correlation between soil loss and sediment delivery and expansion of cultivated area is highly significant (p < 0.001). Sub-watershed six (SW-6) showed the highest soil loss (23.17 t/ha/year) while sub-watershed two (SW- 2) has the lowest soil loss (5.54 t/ha/year). This is because SW-2 is situated in the lower reaches of the watershed under dense vegetation cover experiencing less erosion. The findings on the erosion hotspots presented in this study allow prioritizing the segments of the watershed that need immediate application of improved management interventions and informed decision-making processes.

Cassava response to the integrated use of manure and NPK fertilizer in Zambia.

Cassava is Africa's second most important food source in terms of calories consumed per capita. However, farmers use little or no fertilizer on cassava and scant information is available regarding the cassava yield response to mineral and organic fertilizer inputs in Zambia. This study was undertaken to determine the response of cassava to the integrated use of organic and inorganic nutrient sources in two contrasting agroecological zones of Zambia; Mansa located in Zone III and Kabangwe located in Zone II. The treatments consisted of a factorial combination of four NPK rates (unfertilized control, 50N-11P-41.5K, 100N-22P-83K, and 150N-33P-124.5K kg/ha) with four rates of chicken manure (0, 1.4, 2.8, and 4.2 t/ha). The treatments were laid out in a randomized complete block design with three replications. Cassava height, stem girth, canopy diameter, leaf area index, and chlorophyll index were monitored over time and roots were harvested at 12 months after planting (MAP). Growth parameters and yield varied significantly (p < 0.01) both with NPK, manure application, and their interaction effects at 12 MAP. The combined application of 4.2 t/ha of chicken manure and 100N-22P-83 K kg/ha of mineral fertilizer resulted in the highest yields of 35.2 t/ha at Kabangwe. But, the highest average yield of 34.4 t/ha was recorded with the application of 2.8 t/ha manure and 100N-22P-83 K kg/ha mineral fertilizer at Mansa. This increased treatment yield by 24 and 29% over the sole NPK fertilizer application at Mansa and Kabangwe sites, respectively. Harvest index (HI) was higher when 2.8 t/ha chicken manure was applied in combination with 50N-11P-41.5K kg/ha at Kabangwe. But, the highest HI at Mansa site was achieved with the combination of 2.8 t/ha manure and 100N-22P-83 K kg/ha. This combination also resulted in the highest agronomic efficiency of N, P and K at both sites. It is concluded that cassava productivity and nutrient use efficiency can be improved through the integrated use of NPK and manure in Zambia.