Soil carbon sequestration, carbon markets, and conservation agriculture practices: A hypothetical examination in Mozambique

Pages 167–179

Timoteo E. Simone, Dayton M. Lambert, Ivan Cuvaca, Neal S. Eash

 

Measuring flow velocity on frozen and non-frozen slopes of black soil through leading edge method

Pages 180–189

Chao Chen, Yunyun Ban, Xuefeng Wang, Tingwu Lei

 

Dredging effects on selected nutrient concentrations and ecoenzymatic activity in two drainage ditch sediments in the lower Mississippi River Valley

Pages 190–195

Matt Moore, Martin A. Locke, Michael Jenkins, Robert W. Steinriede, Daniel S. McChesney

 

The evaluation/application of Hydrus-2D model for simulating macro-pores flow in loess soil

Pages 196–201

Xuexuan Xu, Shahmir Ali Kalhoro, Wenyuan Chen, Sajjad Raza

 

Grid-cell based assessment of soil erosion potential for identification of critical erosion prone areas using USLE, GIS and remote sensing: A case study in the Kapgari watershed, India

Pages 202–211

Gurjeet Singh, Rabindra Kumar Panda

 

Deposition of eroded soil on terraced croplands in Minchet catchment, Ethiopian Highlands

Pages 212–220

Alemtsehay Subhatu, Tatenda Lemann, Kaspar Hurni, Brigitte Portner, ... Hans Hurni

 

Estimating landscape susceptibility to soil erosion using a GIS-based approach in Northern Ethiopia

Pages 221–230

Lulseged Tamene, Zenebe Adimassu, Ermias Aynekulu, Tesfaye Yaekob

 

Soil and water conservation effects on soil properties in the Middle Silluh Valley, northern Ethiopia

Pages 231–240

Solomon Hishe, James Lyimo, Woldeamlak Bewket

 

The effect of grid size on the quantification of erosion, deposition, and rill network

Pages 241–251

Xiaoyu Lu, Yingkui Li, Robert A. Washington-Allen, Yanan Li, ... Qingwu Hu

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Free full papers and open access are available at ScienceDirect : http://www.sciencedirect.com/science/journal/20956339

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Soil carbon sequestration, carbon markets, and conservation agriculture practices: A hypothetical examination in Mozambique

Pages 167–179

Timoteo E. Simone, Dayton M. Lambert, Ivan Cuvaca, Neal S. Eash

Abstract

Payments for Environmental Services (PES) are relatively novel mechanisms whereby the adoption of sustainable management practices by a stakeholder is rewarded by incentives linked to external markets. Adoption of PES for conservation agricultural practices (CAPS) by smallholder farmers may provide opportunities to increase household income or cover the technology costs of adoption if the carbon sequestration benefits of CAPS are quantifiable, adoption rates are accelerated and maintained, a mechanism exists whereby carbon sequestration services can be compensated, and carbon offset exchange markets are viable. This research suggests a methodology to examine a PES market for carbon offsets generated by the adoption of CAPS by farmers in Mozambique. Assuming a cumulative adoption of 60% over a 20-year period, revenue from PES market participation to CA adopters was two times higher than revenue earned when disadoption occurred midway through the simulation. Lower adoption targets are associated with higher per household returns when fertilizer rates typical to the region are increased. Establishing and maintaining a sustainable PES system in the study region would require significant investment in time and resources. The lack of on-the-ground institutions or local support for such a program would also challenge successful implementation. Finally, the programs where participant success depends on external markets, such as the hypothetical one suggested here, are subject to the ebb and flow of foreign demand for carbon offsets. Addressing these three broad constraints to a PES/CAPS program in the region would require grass-roots driven policy initiatives with buy-in at multiple social, economic, and political levels.

 

Measuring flow velocity on frozen and non-frozen slopes of black soil through leading edge method

Pages 180–189

Chao Chen, Yunyun Ban, Xuefeng Wang, Tingwu Lei

Abstract

Flow velocity is a major parameter related to hillslope hydrodynamics erosion. This study aims to measure flow velocity over frozen and non-frozen slopes through leading edge method before being calibrated with accurate flow velocity to determine the correct coefficient for convenience of flow velocity measurement. Laboratory experiments were conducted on frozen and non-frozen soil slopes with flumes involving four slope gradients of 5°, 10°, 15°, and 20°and three flow rates of 1, 2, and 4 L/min with a flume of 6 m long and 0.1 m wide. The measurements were made with a stopwatch to record the time duration that the water flow ran over the rill segments of 2, 4 and 6 m long. Accurate flow velocity was measured with electrolyte trace method, under pulse boundary condition. The leading edge and accurate flow velocities were used to determine the correction coefficient to convert the former to the latter. Results showed that the correction coefficient on frozen soil slope was 0.81 with a coefficient of determination (R2) of 0.99. The correction coefficient on non-frozen soil slope was 0.79 with R2 of 0.98. A coefficient of 0.8 was applicable to both soil surface conditions. The accurate velocities on the four frozen black soil slopes were approximately 30%, 54%, 71%, and 91% higher than those on non-frozen soil slopes. By contrast, the leading edge flow velocities on the frozen soil slopes were 23%, 54%, 67%, and 84% higher than those on non-frozen soil slopes. The flow velocities on frozen soil slopes increased with flow rate at all four slopes, but they increased from 5 to 15° before getting stabilized. Therefore, rill flow velocity can be effectively measured with leading edge method by multiplying the leading edge velocity with a correction coefficient of 0.80. This study provides a strategy to measure rill flow velocity for studies on soil erosion mechanisms.

 

Dredging effects on selected nutrient concentrations and ecoenzymatic activity in two drainage ditch sediments in the lower Mississippi River Valley

Pages 190–195

Matt Moore, Martin A. Locke, Michael Jenkins, Robert W. Steinriede, Daniel S. McChesney

Abstract

Agricultural drainage ditches are conduits between production acreage and receiving aquatic systems. Often overlooked for their mitigation capabilities, agricultural drainage ditches provide an important role for nutrient transformation via microbial metabolism. Variations in ecoenzyme activities have been used to elucidate microbial metabolism and resource demand of microbial communities to better understand the relationship between altered nutrient ratios and microbial activity in aquatic ecosystems. Two agricultural drainage ditches, one in the northeast portion of the Arkansas Delta and the other in the lower Mississippi Delta, were monitored for a year. Sediment samples were collected prior to each ditch being dredged (cleaned), and subsequent post-dredging samples occurred as soon as access was available. Seasonal samples were then collected throughout a year to examine effects of dredging on selected nutrient concentrations and ecoenzymatic activity recovery in drainage ditch sediments. Phosphorus concentrations in sediments after dredging decreased 33–66%, depending on ditch and phosphorus extraction methodology. Additionally, ecoenzymatic activity was significantly decreased in most sediment samples after dredging. Fluorescein diacetate hydrolysis activity, an estimate of total microbial activity, decreased 56–67% after dredging in one of the two ditches. Many sample sites also had significant phosphorus and ecoenzymatic activity differences between the post-dredge samples and the year-long follow-up samples. Results indicate microbial metabolism in dredged drainage ditches may take up to a year or more to recover to pre-dredged levels. Likewise, while sediment nutrient concentrations may be decreased through dredging and removal, runoff and erosion events over time tend to quickly replenish nutrient concentrations in replaced sediments. Understanding nutrient dynamics and microbial metabolism within agricultural drainage ditches is a crucial step toward addressing issues of nutrient enrichment in aquatic receiving systems, especially those contributing to the Gulf of Mexico.

 

The evaluation/application of Hydrus-2D model for simulating macro-pores flow in loess soil

Pages 196–201

Xuexuan Xu, Shahmir Ali Kalhoro, Wenyuan Chen, Sajjad Raza

Abstract

Soil hydraulic properties were mainly governed by soil structures especially when the structures is full of the connected soil macro-pores. Therefore, the good hydrological models need to be well documented for revealing the process of soil water movement affected by soil medium. The Hydrus-2D model with double domain was recommended in simulating water movement in a heterogeneous medium of soil. To evaluate the performance of the double domain Hydrus-2D model in loess soil, the dynamic of soil wetting front movement in differential loess soil columns under the constant water head were observed and the processes was simulated by Hydrus-2D model under conditions of different soil properties. The results indicated that the Hydrus-2D model was quite good in simulation of loess soil water movements, and the relative errors of simulation results are less than 15%, MRE less than 5%, and R2>0.9. The results provided the appropriate infiltration parameters of loess soil.

 

Grid-cell based assessment of soil erosion potential for identification of critical erosion prone areas using USLE, GIS and remote sensing: A case study in the Kapgari watershed, India

Pages 202–211

Gurjeet Singh, Rabindra Kumar Panda

Abstract

Estimation of soil erosion is of paramount importance due to its serious environmental and societal concern. Soil erosion would have impact on fertility of agricultural land and quality of water. The major objective of this study was to investigate the spatial heterogeneity of annual soil erosion on the grid-cell basis in a small agricultural watershed of eastern India. The study watershed has a drainage area of 973 ha and is subdivided into three sub-watersheds namely: KGSW1, KGSW2 and KGSW3, based on the land topography and drainage network. Average annual soil erosion was estimated on 100 m×100 m grid-cells by integrating universal soil loss equation (USLE) model with GIS for subsequent identification of critical erosion prone areas. It was found that 82.63% area of the total watershed falls under slight-erosion-class (0–5 t-ha−1-yr−1), 6.87% area lies under the moderate-erosion-class (5–10 t-ha−1-yr−1), 5.96% area is under high-erosion-class (10–20 t-ha−1-yr−1), 3.3% area of watershed lies under the very-high-erosion-class (20–40 t-ha−1-yr−1) and 1.24% area falls under “severe-erosion-class” (40–80 t-ha−1-yr−1). The study revealed that the sub-watershed KGSW3 is critical due to the presence of the highest number of critical erosion prone grid-cells. The sediment delivery ratio (SDR) was also estimated to analyze the contribution of sediment yield at the sub-watershed level. Lowest SDR for the whole watershed as compared to sub-watersheds indicates that most of the eroded soil got deposited in rice crop check-basins before reaching the outlet. The reported results can be used for prioritizing critical erosion prone areas and for determining appropriate soil erosion prevention and control measures.

 

Deposition of eroded soil on terraced croplands in Minchet catchment, Ethiopian Highlands

Pages 212–220

Alemtsehay Subhatu, Tatenda Lemann, Kaspar Hurni, Brigitte Portner, ... Hans Hurni

Abstract

In the Ethiopian Highlands, soil and water conservation practices are of utmost importance to conserve eroded soil and combat soil loss. This study provides detailed results on on-site sediment deposition and net soil loss in terraced croplands in a catchment in the sub-humid Ethiopian Highlands. Sediment deposition was measured on horse bean and maize fields during the crop growing seasons of 2014 and 2015. Measurements took place on observation plots on terraced cropland with varying spacing between terraces and varying slope gradients. Net soil loss, in this case the amount leaving the terraced cropland, was calculated by modelling the Universal Soil Loss Equation (USLE) for the whole observation field and subtracting the measured sediment deposition. The study result showed about 8–11 t ha−1 sediment was deposited in the deposition zone of the terraced cropland, with greater sediment deposition on terraces with narrow spacing and steeper slope gradients. Sediment deposition was highest in July and August, and relatively low in September. Annual soil loss ranged from 32 to 37 t ha−1 in the terraced cropland of the study area. From the total soil loss in the crop growing season, about 54–74% sediment was deposited on the deposition zone of terraced crop fields. Implementation of soil and water conservation with narrow spacing, especially on the steep slopes of the sub-humid Ethiopian Highlands or other similar area, are thus highly recommended as they enable conservation of the eroded soil in the cropland.

 

Estimating landscape susceptibility to soil erosion using a GIS-based approach in Northern Ethiopia

Pages 221–230

Lulseged Tamene, Zenebe Adimassu, Ermias Aynekulu, Tesfaye Yaekob

Abstract

Soil erosion is a very critical form of land degradation resulting in the loss of soil nutrients and downstream sedimentation of water storages in the highlands of Ethiopia. As it is technically and financially impossible to conserve all landscapes affected by erosion, identification of priority areas of intervention is necessary. Spatially distributed erosion models can help map landscape susceptibility to erosion and identify high erosion risk areas. Integration of erosion models with geographic information systems (GIS) enables assessing evaluate the spatial variability of soil erosion and plan implementing conservation measures at landscape levels. In this study, the Revised Universal Soil Loss Equation adjusted for sediment delivery ratio was used in a GIS system to assess landscape sensitivity to erosion and identify hotspots. The approach was applied in three catchments with size being 10–20 km2 and results were compared against quantitative and semi-quantitative data. The model estimated mean soil loss rates of about 45 t ha−1 y−1 with an average variability of 30% between catchments. The estimated soil loss rate is above the tolerable limit of 10 t ha−1 y−1. The model predicted high soil loss rates at steep slopes and shoulder positions as well as along gullies. The results of the study demonstrate that knowledge of spatial patterns of high soil loss risk areas can help deploy site-specific conservation measures.

 

Soil and water conservation effects on soil properties in the Middle Silluh Valley, northern Ethiopia

Pages 231–240

Solomon Hishe, James Lyimo, Woldeamlak Bewket

Abstract

Community-based Soil and Water Conservation (SWC) practices have been adopted in the Tigray region since 1991 for restoration of the degraded landscape. The effects of those conservation measures on physico-chemical properties of soil were limitedly studied. Thus, this study evaluated the effects of SWC on selected soil properties in the Middle Silluh Valley, Tigray region, Northern Ethiopia. The study considered conserved landscapes (terraced hillside, terraced farmland and exclosure area) and non-conserved landscapes (non-terraced hillside, non-terraced farmland and open grazing land) for comparison using a one-way analysis of variance (ANOVA). A total of 24 samples were collected from each landscape at a depth of 10–30 cm. The results indicated that mean bulk density (BD) was low on terraced hillside, non-terraced hillside and exclosure area. Sand and clay content were significantly different at P <0.05 for the six landscape categories. Higher mean organic matter was observed in the conserved landscape, as compared with the corresponding non-conserved landscape. Pearson's correlation between Soil Organic Matter (SOM) and clay content, SOM and Total Nitrogen (TN) showed strong positive relationships. Overall, the results show that SWC had significantly positive effects on soil's physical and chemical properties in the study area.

 

The effect of grid size on the quantification of erosion, deposition, and rill network

Pages 241–251

Xiaoyu Lu, Yingkui Li, Robert A. Washington-Allen, Yanan Li, ... Qingwu Hu

Abstract

Hillslope rill/interrill erosion has been investigated from the perspective of runoff transport of sediment. Recent advances in terrestrial laser scanning can provide high-resolution elevation data up to centimeter levels, and temporal digital elevation models (DEMs) enabled the detection and quantification of sediment redistribution. Erosion and deposition are spatially heterogeneous across hillslopes, and the choice of resolution is critical when using a DEM to study the spatial pattern of the processes. This study investigates the influence of grid size on the sediment change calculation and rill network delineation based on two surveys using a terrestrial laser scanner on a hillslope with well-developed rills in 2014 and 2015. Temporal DEMs were used to quantify elevation changes and used to delineate rill networks. We produced DEM pairs of incremental grid sizes (1-cm, 2-cm, 5-cm, 8-cm, 10-cm, 15-cm, 20-cm, and 30-cm) for DEM difference and rill network delineation. We used the 1-cm DEM as the reference to compare the results produced from other DEMs. Our results suggest that erosion mainly occurs on the rill sidewalls, and deposition on the rill floors, with patches of erosion/deposition within the interrill areas. Both the area and volume of detectable change decrease as the grid size increases, while the area and volume of erosion are less sensitive compared to those of deposition. The total length and number of rills decrease with the increased grid size, whereas the average length of rills increases. The mean offset between delineated rill network and the reference increases with larger grid sizes. In contrast to the erosion and deposition detected within rills, minor changes are detected on the interrill areas, indicating that either no topographic changes occurred or the changes were too small to be detected on the interill areas by our finest 1-cm DEMs. We recommend to use the finest possible grid size that can be achieved for future studies.