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Finding effective ecosystem services (ESS) management practices to counteract land degradation and poverty is becoming increasingly urgent in the Ethiopian highlands, where livelihood security is strongly dependent on local ESS, particularly those provided by water and soil. In this paper, we test the effects of widely implemented soil and water conservation (SWC) interventions on storm flow and sediment concentration in the Debre Mawi watershed (representative of watersheds in the upper Blue Nile basin and Ethiopian highlands). The SWC interventions were tested with a Parameter Efficient Distributed (PED) model. The PED model simulates saturation excess runoff from degraded and saturated valley bottoms, and base and interflow from hillsides. The model was calibrated with observed runoff and sediment data in a 95-ha subcatchment. We found that the PED model simulated the discharge and soil loss well by decreasing the proportion of degraded lands due to installing SWC practices. The results show that four years after the implementation of SWC practices, the infiltration of rainwater was improved in 53% of the degraded lands. Thus, installing SWC practices on hillsides where infiltration is limited is most beneficial and will result in greater water availability during the dry phase, especially in locations where volcanic dikes block the lateral flow. [ABSTRACT FROM AUTHOR]

This study employed geomorphometric analysis to characterize the four major watersheds (Gilgel Abay, Gumara, Rib, and Megech) of Lake Tana sub-basin, Ethiopia, and prioritize the watersheds for the implementation of SWC practices using GIS and remote sensing techniques. Also, the study analyzed streamflow and sediment data recorded at the outlets of each watershed to associate the geomorphometric prioritization result with recordings of the watersheds. Geomorphometric analysis results indicated that the Rib watershed is the most susceptible watershed for soil erosion and should be prioritized for the implementation of SWC practices. The analysis of streamflow and suspended sediment concentration suggest that the Rib watershed had the second maximum sediment yield (14.3 t ha−1 yr−1) compared to the other three watersheds. This is because of the low streamflow response of the watershed compared with the Gumara watershed which had the highest sediment yield (18.9 t ha−1 yr−1). [ABSTRACT FROM AUTHOR]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jenvman.2010.03.019 Byline: Joshua W. Faulkner, Zachary M. Easton, Wei Zhang, Larry D. Geohring, Tammo S. Steenhuis Abstract: Vegetative treatment areas (VTAs) are commonly being used as an alternative method of agricultural process wastewater treatment. However, it is also apparent that to completely prevent discharge of pollutants to the surrounding environment, settling of particulates and bound constituents from overland flow through VTAs is not sufficient. For effective remediation of dissolved agricultural pollutants, VTAs must infiltrate incoming wastewater. A simple water balance model for predicting VTA soil saturation and surface discharge in landscapes characterized by sloping terrain and a shallow restrictive layer is presented and discussed. The model accounts for the cumulative effect of successive rainfall events and wastewater input on soil moisture status and depth to water table. Nash-Sutcliffe efficiencies ranged from 0.65 to 0.81 for modeled and observed water table elevations after calibration of saturated hydraulic conductivity. Precipitation data from relatively low, average, and high annual rainfall years were used with soil, site, and contributing area data from an example VTA for simulations and comparisons. Model sensitivity to VTA width and contributing area (i.e. barnyard, feedlot, silage bunker, etc.) curve number was also investigated. Results of this analysis indicate that VTAs should be located on steeper slopes with deeper, more-permeable soils, which effectively lowers the shallow water table. In sloping landscapes (>2%), this model provides practitioners an easy-to-use VTA design and/or risk assessment tool that is more hydrological process-based than current methods. Author Affiliation: Department of Biological and Environmental Engineering, Cornell University, 62 Riley-Robb Hall, Ithaca, NY 14850, USA Article History: Received 16 September 2009; Revised 16 March 2010; Accepted 27 March 2010

Fire is commonly used to establish and maintain pastures in the Amazon. Fire is also known to induce soil water repellency but few published data exist for the humid tropics. The objectives of this study were to characterise the intensity and spatial variability of water repellency on previously burned pasture soils in the Amazon, and its effect on the nutrient status of the forage grass Brachiaria brizantha (Hochst.) Stapf. Surface soils of pastures and forests in north-western Mato Grosso, Brazil, were found to exhibit soil water repellency using MED and WDPT tests. Soil water repellency was found only within 0-0.01 m of the mineral soil surface, with soil below 0.01 m found to be hydrophilic in all cases. Spatial variability of repellency was high for both pasture and forest soils. For pasture soils, soil water repellency was strongest on recently burned pastures, which exhibited some extremely high values (MED >8 M). Repellency decreased rapidly with time following burning. Increasing soil water repellency was associated with decreasing N:P ratios or B. brizantha above-ground biomass ([r.sup.2] = 0.66, P= 0.004). These findings indicate that soil water repellency and pasture productivity are inversely related. Since pasture abandonment fuels continued deforestation, disrupting the processes causing pasture degradation may lead to more sustainable land use in the Amazon. Additional keywords: hydrophobicity, Brachiaria brizantha, burning, N : P, Oxisol, Ultisol., Introduction Over 75% of Amazonian deforestation in the past 30 years has been directed towards the establishment of pastures (Fearnside 1996). The productivity of Amazonian pastures declines within 4-8 years [...]

The control of soil moisture, vegetation type, and prior land use on soil health parameters of perennial grass cropping systems on marginal lands is not well known. A fallow wetness-prone marginal site in New York (USA) was converted to perennial grass bioenergy feedstock production. Quadruplicate treatments were fallow control, reed canarygrass (Phalaris arundinaceae L. Bellevue) with nitrogen (N) fertilizer (75 kg N ha−1), switchgrass (Panicum virgatum L. Shawnee), and switchgrass with N fertilizer (75 kg N ha−1). Based on periodic soil water measurements, permanent sampling locations were assigned to various wetness groups. Surface (0-15 cm) soil organic carbon (SOC), active carbon, wet aggregate stability, pH, total nitrogen (TN), root biomass, and harvested aboveground biomass were measured annually (2011-2014). Multi-year decreases in SOC, wet aggregate stability, and pH followed plowing in 2011. For all years, wettest soils had the greatest SOC and active carbon, while driest soils had the greatest wet aggregate stability and lowest pH. In 2014, wettest soils had significantly (p < 0.0001) greater SOC and TN than drier soils, and fallow soils had 14 to 20% greater SOC than soils of reed canarygrass + N, switchgrass, and switchgrass + N. Crop type and N fertilization did not result in significant differences in SOC, active carbon, or wet aggregate stability. Cumulative 3-year aboveground biomass yields of driest switchgrass + N soils (18.8 Mg ha−1) were 121% greater than the three wettest switchgrass (no N) treatments. Overall, soil moisture status must be accounted for when assessing soil dynamics during feedstock establishment. [ABSTRACT FROM AUTHOR]

Quantifying components of soil water balance in farmland of the middle reaches of Heihe River Basin is essential for efficiently scheduling and allocating limited water resources for irrigation in this arid region. A soil water balance model based on empirical assumptions in the vadose zone of farmland was developed and simulation results were compared/validated with results by the numerical model HYDRUS-1D. Results showed a good coherence between the simulated results of the water balance models and the HYDRUS-1D model in soil water storage, evapotranspiration, deep percolation and groundwater recharge, which indicated that the water balance model was suitable for simulating soil water movement in the study area. Considering the spatial distribution of cropping patterns, groundwater depth and agricultural management, ArcGIS was applied for the pre-/post-processing of the water balance model to quantify the spatial distribution of components of soil water balance in the major cropland in middle reaches of Heihe River Basin. Then, distributions of components of soil water balance in the major cropland under different water-saving irrigation practices during the growing season were predicted and discussed. Simulation results demonstrated that evapotranspiration of the main crops would be more prominently influenced by irrigation quota under deep groundwater depth than that under shallow groundwater depth. Groundwater recharge would increase with the increase of irrigation quota and decrease with the increase of groundwater depth. In general, when groundwater depth reached 3 m, groundwater recharge from root zone was negligible for spring wheat. While when it reached 6 m, groundwater recharge was negligible for maize. Water-saving irrigation practices would help to reduce groundwater recharge with a slight decrease of crop water consumption. [ABSTRACT FROM AUTHOR]

Most semi-distributed watershed water quality models divide the watershed into hydrologic response units (HRU) with no flow among them. This is problematic when watersheds are delineated to include variable source areas (VSAs) because it is the lateral flows from upslope areas to downslope areas that generate VSAs. Although hydrologic modellers have often successfully calibrated these types of models, there can still be considerable uncertainty in model results. In this paper, a topographic-index-based method is described and tested to distribute effective soil water holding capacity among HRUs, which can be subsequently adjusted using the watershed baseflow coefficient. The method is tested using a version of the Soil and Water Assessment Tool (SWAT) model that simulates VSA runoff and is applied to two watersheds: a New York State (NYS) watershed, and one in the head waters of the Blue Nile Basin (BNB) in Ethiopia. Daily streamflow predicted using effective soil water storage capacities based only on the topographic index were reassuringly accurate in both the NYS watershed (daily Nash Sutcliffe ( E) = 0·73) and in the BNB ( E = 0·70). Using the baseflow coefficient to adjust the effective soil water storage capacity only slightly improved streamflow predictions in NYS ( E = 0·75) but substantially improved the BNB predictions ( E = 0·80). By comparison, the standard SWAT model, which uses the traditional look-up tables to determine a runoff curve number, performed considerably less accurately in un-calibrated form ( E = 0·51 for NYS and E = 0·45 for BNB), but improved substantially when explicitly calibrated to streamflow measurements ( E = 0·76 for NYS and E = 0·67 for the BNB). The calibration method presented here provides a parsimonious, systematic approach to using established models in VSA watersheds that reduces the ambiguity inherent in model calibration. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: Grain production shortfalls in northern Ethiopia are commonly associated with occurrence of intra-seasonal dry spells or droughts and rapid land degradation which adversely impact crop yields. Suitable practices that use available rainwater more efficiently to mitigate impact of dry spells on crops and that protect soil are needed to stabilize and improve grain yields in the predominately rainfed agriculture. During three cropping seasons on-farm experiments tested conservation tillage techniques implemented with oxen-drawn plows on clay loam soil. Tested tillage techniques are subsoiling, open and tied ridges, no till, and conventional tillage with the local maresha plow (the control). Effectiveness in improving root zone soil moisture, limiting soil erosion, and improving sorghum (Sorghum bicolor (L.) Moench.) and chickpea (Cicer arietinum L.) grain yield were determined. Results demonstrate that performance of the tillage techniques varied with seasonal rainfall distribution and intensity and land slope gradient. Tied and open ridge increased seasonal root zone soil moisture 15–24%. Subsoiling slightly (3%) increased and no till slightly decreased soil moisture but were not statistically different from conventional tillage. Tied ridge and no till significantly reduced seasonal soil loss by up to 11Mgha−1 during seasons with moderate intensity storms, but during a season with high intensity storms tied ridge on over 9% slope gradient increased soil loss (up to 35Mgha−1). The increased soil disturbance of subsoiling led to higher soil loss rates (up to 32Mgha−1) than conventional tillage during all seasons. Grain yield decreased and runoff and erosion rates increased rapidly with increasing land slope gradient. During a season with moderate intensity rainfall open and tied ridge increased sorghum yield by 67–73% over the control (730kgha−1) while no till decreased yield by 25%. During a season when high intensity rainfall events damaged the ridges, subsoiling had the best sorghum yield with 42% increase over the control (1430kgha−1). Poor early season rainfall and fungus attacks resulted in low chickpea yields (200–320kgha−1) and statistically insignificant differences between tillage methods. Overall results of the study suggest that on slopes below 8% gradient oxen-drawn ridge tillage and subsoiling, to a lesser degree, can effectively improve conditions that mitigate impact of short dry spells especially during seasons with less intense rainfall events. [Copyright &y& Elsevier]

A curve number based model, Soil and Water Assessment Tool (SWAT), and a physically based model, Soil Moisture Distribution and Routing (SMDR), were applied in a headwater watershed in Pennsylvania to identify runoff generation areas, as runoff areas have been shown to be critical for phosphorus management. SWAT performed better than SMDR in simulating daily streamflows over the four-year simulation period (Nash-Sutcliffe coefficient: SWAT, 0.62; SMDR, 0.33). Both models varied streamflow simulations seasonally as precipitation and watershed conditions varied. However, levels of agreement between simulated and observed flows were not consistent over seasons. SMDR, a variable source area based model, needs further improvement in model formulations to simulate large peak flows as observed. SWAT simulations matched the majority of observed peak flow events. SMDR overpredicted annual flow volumes, while SWAT underpredicted the same. Neither model routes runoff over the landscape to water bodies, which is critical to surface transport of phosphorus. SMDR representation of the watershed as grids may allow targeted management of phosphorus sources. SWAT representation of fields as hydrologic response units (HRUs) does not allow such targeted management. [ABSTRACT FROM AUTHOR]

Minasny et al. (2020) proposed enhancing future global soil science research by examining the role of soils in global ecosystem functioning. They argued in particular that meaningful collaboration between high- and low-income countries is essential to generate new knowledge and facilitate capacity building. In this commentary, we provide an account of our experience with an effective cooperative research and training partnership between Cornell University and Bahir Dar University in Ethiopia. We note that, in addition to the willingness and commitment of the scientists to cooperate, support and flexibility of senior university administrators is essential for international cooperation to succeed. We illustrate these points describing our experience and show that these cooperative efforts are evolving incrementally and in many cases do not follow well-laid-out programs. [ABSTRACT FROM AUTHOR]

Urine-treated soils have been implicated as an important source of gaseous N losses to the atmosphere. The goal of our research was to quantify NH3 and N2O emissions from urine under different simplified and controlled soil conditions and to relate these results to urinary-N transformation processes in soil. We studied the influence of soil texture (coarse vs. fine sand), moisture distribution with depth, air-filled pore space, and rate of air movement, which affected both soil drying processes and emission rates. Laboratory experiments were performed with synthetic urine in both aerobic and anaerobic conditions. Texture was the most important factor controlling NH3 volatilization and N2O emission factors in urine-treated sands. Generally, the finer the sand texture, the higher the input of denitrification to the total N2O emissions; however, the air-filled pore space threshold, below which denitrification became dominant, was greater in coarse sand. In addition, the evaporation rate of the urine water component was found to be an important parameter in total NH3 and N2O emissions. Ammonia volatilization occurred during the first day of the treatments, with volatilization rates closely related to evaporation rates in both sand textures. Finer sand texture caused reductions in the urine evaporation rate and therefore in NH3 volatilization rates. Urine evaporation increased air-filled pore space, thereby improving aeration conditions in the sand that contribute to nitrification dominance of N2O production. Moreover, evaporation of urine, enriched with dissolved N2O, increased total N2O emission. Results from these simplified experiments need confirmation under field soil conditions. [ABSTRACT FROM AUTHOR]

Highlights • Soil moisture and yield were observed for 6-year grain, forage and bioenergy crops. • Potential bioethanol production and groundwater decline were calculated. • Sorghum rotation produced more bioethanol per unit of groundwater decline. • Net groundwater withdrawal for perennial switchgrass was the smallest. Abstract Managing the complex demands on available energy, food and water is a fundamental challenge for a world with increasingly tenuous resource pools. The North China Plain's groundwater crisis has become increasingly serious due to decades-long over-exploitation for irrigation to pursue high grain yield. This combined challenge motivated investigation of ways to mitigate the groundwater table decline while fostering the use of renewable bioenergy resources. To provide insights about tradeoffs among water, food and energy, we performed a six-year experiment from 2010 to 2015 in the North China Plain where groundwater use, biomass and biofuel production and water use efficiency were compared for four cropping systems. They are winter wheat-summer maize (WM, grains, 1-year cycle), ryegrass–sweet sorghum (RS, forage plus bioenergy crops, 1-year cycle), winter wheat–summer maize→ ryegrass–sweet sorghum (WMRS, forage, bioenergy plus grain crops, 2-year cycle), and perennial switchgrass (SG, bioenergy crop). Actual evapotranspiration (ET a) and recharge to groundwater were calculated and validated using observed soil moisture contents. Results showed ET a of the cropping systems were statistically similar ranging from 694 to 730 mm yr−1 with the exception of switchgrass which was significantly less at 504 mm yr-1. The water table was projected to decline by about 1.3 m yr-1 for all three multi-crop rotations and 0.4 m yr-1 for switchgrass. In terms of bioethanol production per unit land and per unit ET a , the ryegrass-sweet sorghum (RS) rotation performed best with 25.0 m3 ha-1 and 5.7 L m-3 outperforming the yearly winter wheat–summer maize (WM) rotation (11.7 m3 ha-1 and 3.3 L m-3) and switchgrass (11.4 m3 ha-1 and 2.6 L m-3). The multiple year rotation of winter wheat–summer maize→ ryegrass–sweet sorghum (WMRS) yielded 16.9 m3 bioethanol per hectare and 4.3 L m-3 bioethanol per m3 ET a. When optimizing bioethanol against net groundwater depletion, RS and switchgrass outperformed the two grain-based rotations with 15.5 L and 14.4 L of bioethanol per m3 of depleted groundwater, ahead of WMRS at 10.9 L m-3 and WM at 9.1 L m-3. These results are significant for setting governmental policies on sustainable use of groundwater by various crop mixes. [ABSTRACT FROM AUTHOR]

Abstract Soil is a critical medium that governs hydrological processes in a landscape; however, soil data quality and resolution are not given much emphasis during watershed modeling and developing practical management practices, especially in data scarce regions such as in the Ethiopian highlands. This is primarily because measuring most soil parameters is costly, laborious, and at times impractical. Infiltration models and Pedotransfer functions (PTFs) may bridge this gap by estimating such complex soil parameters from easily measurable ones. However, most infiltration models and PTFs were developed for temperate regions and there is no comprehensive experimental or modeling work done to evaluate the robustness of such approaches in the Ethiopian highlands. Therefore, this study aims to i) evaluate the performance of three infiltration models, namely Horton, Koistakov, and Philip in simulating soil infiltration rates and ii) test the reliability of nine PTFs in estimating saturated hydraulic conductivity and soil moisture contents at field capacity and permanent wilting point in a case study in the Anjeni watershed. Soils in the Anjeni watershed on average contain higher percentages of clay and silt with 42 and 34%, respectively; and have acidic pH and low organic matter. Steady infiltration rate (f s) and saturated hydraulic conductivity (Ks) ranged between 0.19 and 30.6 mm h−1 and 0.19 and 3.3 mm h−1, respectively. All the three infiltration models fitted observed data very well with R2 and Nash-Sutcliffe efficiency (NS) values between 0.95 and 0.97 each. While the Horton and Koistakov models had the same R2 and NS values, the Horton provided smaller Mean Absolute Error (MAE) and Root Mean Square Error (RMSE) values. Some of the tested PTFs showed promising results in estimating saturated hydraulic conductivity and soil moisture content; however, all PTFs showed limitations which warrant further evaluation using observed data. This study showed that soil hydrologic parameters vary significantly even within a small area, and widely available soil datasets (e.g., Africa Soil Information Service (AfSIS) and FAO Harmonized World Soil Database) fail to reflect actual field conditions. This suggests that emphasis should be given to soil data quality and resolution during watershed modeling, and land and water management planning. Highlights • The FAO and African Soil Information Service (AfSIS) datasets did not accurately represent field soil conditions • XRD test results showed that most soils in the Anjeni watershed were mixtures of kaolinite, illite, and quartz • The Horton, Koistakov, and Philip infiltration models fitted observed data very well • Pedotransfer functions could be viable options in data scarce regions liken in the Ethiopian highlands • There was no difference in performances between PTFs developed based on observations from temperate and African regions • Tested PTFs showed some limitations which warrant further evaluation using observed data [ABSTRACT FROM AUTHOR]

Abstract The effect of long-term versus short-term water content on soil organic carbon (SOC) mineralizability was evaluated in a six-week incubation trial. Soils were sampled from field sites in upstate New York used for rain-fed bioenergy crop production: nitrogen (N)- fertilized reed canarygrass, switchgrass, switchgrass + N, as well as a broadleaf-grass fallow. Within each cropping system, natural moisture gradients due to topography and subsoil structure allowed us to sample across regions with high (0.5 g g−1), mid (0.4 g g−1) and low (0.3 g g−1) water content. Moisture of the laboratory incubations was adjusted mimicking the three average field moisture levels in a full factorial design. Increasing laboratory moisture in the incubations increased cumulative carbon mineralization per unit soil (C mineralization) and cumulative C mineralization per unit SOC (C mineralizability) (main effect p < 0.0001), indicating that lower average moisture as found at this site on average limited mineralization but higher average moisture did not. C mineralizability at high field moisture was 31% (25-42%) lower than at low field moisture across all cropping systems, regardless of moisture adjustment in the incubation. The mean slow C pool size of soils from high field moisture sites (997.1 ± 0.1 mg C g−1 C) was 0.2% greater than that of soils from low field moisture sites (p < 0.0001), obtained by fitting a double-exponential model. The mean residence time of the slow mineralizing C pool for soils from low field moisture sites was 5.5 ± 0.1 years, in comparison to 8.0 ± 0.1 years for soils from high field moisture sites (p < 0.0001). While permanganate-oxidizable carbon (POXC) per unit SOC (r = 0.1) was positively correlated to C mineralizability, wet aggregate stability (r = −0.2) was negatively correlated to C mineralizability. Above-ground biomass did not affect C mineralizability (p > 0.05) and root biomass marginally influenced (p = 0.05) C mineralizability after correcting for soil texture variations. Additionally, after correcting for soil texture variations and biomass inputs, C mineralizability significantly decreased with higher field moisture (p = 0.02), indicating possible stabilization mechanisms through mineral interactions of SOC under high water content. Bulk contents of pedogenic iron and aluminum determined by oxalate extraction did not clearly explain differences in mineralizability. However, exchangeable calcium and magnesium contents were significantly (p < 0.0001) greater in high moisture soils than soils with lower moisture. Additionally, cumulative C mineralizability at 6 weeks was negatively correlated to calcium (r = −0.7) and magnesium (r = −0.6) and mean residence time of the modeled slow pool correlated positively with calcium (r = 0.4). Therefore, cation bridging by retained or illuviated base ions was more important than redox changes of iron as a stabilization mechanism in this experiment. Highlights • Soil organic carbon (SOC) was highest in bioenergy plantations under high moisture. • SOC mineralizability was 25–42% lower from high field moisture compared to low field moisture. • Mineralization increased with higher moisture in laboratory incubation. • Above-ground biomass or root biomass did not affect C mineralizability. • Aggregate stability was negatively correlated to C mineralizability. • Base cation contents negatively correlated with mineralizability. [ABSTRACT FROM AUTHOR]

• Use of Berken plow and intercropping with pigeon pea improves soil characteristics. • Root penetration resistance increased with maize roots penetrating 1.2–1.5 times deeper. • Berken plow had the greatest available storage of 56 cm and smallest runoff in both years. • Increases in infiltration resulted in increased soil moisture retention up to 60 cm depth. • Increases in maize productivity resulted in a positive net benefit. Closing the yield gap and enhancing efficiency in rainfed maize production systems in Ethiopia requires urgent action in increasing the productivity of degraded agricultural land. The degradation of land through continuous compaction and decline in the organic matter has resulted in a wide-spread formation of a hardpan that restricts deep percolation, prevents plant root development, and, ultimately can lead to increased erosion. Studies exploring practical low-cost solutions to break the hardpan are limited in Ethiopia. The main objective was to evaluate soil mechanical (i.e. modified plow or Berken plow) or biological intervention (i.e. intercropping with pigeon pea) effectiveness to enhance soil water management and crop yield of rainfed maize systems whilst reducing soil erosion and runoff. Five farm fields, each including four plots with different tillage treatments, were monitored during two rainy seasons in 2016 and 2017. The treatments were: (i) farmers practice under conventional (CT) tillage; plots tilled three times using an oxen driven local plow Maresha , (ii) no-till (NT), (iii) Berken tillage (BT), plots tilled three times using an oxen pulled Berken plow, and (iv) biological (CT + Bio), tap-rooted pigeon pea intercropped with maize on plots conventionally tilled. Results showed that mean tillage depth was significantly deeper in the BT (28 cm) treatment compared to CT and CT + Bio (18 cm) treatments. Measured soil penetration resistance significantly decreased up to 40 cm depth under BT and maize roots reached 1.5 times deeper compared to roots measured in the CT treatment. Under BT, the estimated water storage in the root zone was estimated at 556 mm, 1.86 times higher compared to CT, 3.11 times higher compared to NT and 0.89 times higher compared to CT + Bio. The positive effects on increased water storage and root development resulted in an average increase in maize grain (i.e. 15%, 0.95 t ha−1) and residual above ground biomass (0.3%, 6.4 t ha−1) leading to a positive net benefit of 138 USD ha−1 for the BT treatment compared to the CT treatment. The negative net benefit obtained under CT and CT+Bio was mainly related to the high labor cost related to plowing, weeding, planting, and fertilizer application whilst in the NT this was related to the significantly lower maize yields. The positive effects in the BT treatment, and to some extent the CT+Bio treatment show great potential for smallholder rainfed maize systems where degraded soils with hardpans and high variability in rainfall prevail. [ABSTRACT FROM AUTHOR]

A nine-year (2010–2018) field study in the Debre Mawi watershed was conducted to understand the effect of governmentally-imposed and farmer-initiated conservation practices. The watershed is in the sub-humid Ethiopian Highlands which experience high and increasing erosion rates despite years of conservation efforts. Consequently, reservoirs are filling up with sediment and soil degradation is enhanced, calling for the evaluation of conservation practices currently in use. The few past long-term experimental studies on structural practices are inconclusive. In addition, only anecdotal information is available for streamflow and sediment loss. Precipitation, stream discharge, and suspended sediment concentrations were recorded manually in the Debre Mawi watershed during the nine-year period. Groundwater depth and total saturated area measurements were taken for selected periods. From 2012 to 2014, government-mandated conservation practices were constructed, which consisted of 50-cm-deep infiltration furrows with bunds downslope. These furrows were filled in with sediment by 2018. At the same time, the acreage of eucalyptus trees planted by farmers on the most vulnerable lands tripled to 5% of the total area with most trees fully grown in 2018. Runoff coefficients and sediment concentrations decreased steadily throughout the nine years. In the saturated bottomlands, the observations suggested that government-sponsored infiltration furrows in the saturated bottomlands were ineffective and may concentrate flows and enhance gully erosion, while eucalyptus trees appear effective. The results of this observational study point to both the potential benefits of conservation practices in this sub-humid tropical highland region and to emerging long-term risks. If structural conservation is to be pursued in watersheds like Debre Mawi, due attention must be given to the safe removal of excess water from the valley bottoms. The vegetative farmer-initiated practice of planting eucalyptus trees effectively reduced streamflow and erosion, but at the same time, might dry up wells during the dry monsoon phase which should be investigated further. Image 1 • Acreage of eucalyptus planted by farmers increased three-fold in nine years. • Observed runoff and sediment yield declined with increased acreage of eucalytus. • Dry phase eucalyptus evaporation delayed saturation excess runoff in rain phase. • Infiltration furrows were not maintained, filled up, and appeared ineffective. • Groundwater irrigation is feasible when lava dikes block subsurface downhill flow. [ABSTRACT FROM AUTHOR]