International Soil and Water Conservation Research
Volume 6, Issue 1, Pages 1-78 (March 2018)
Sustainable intensification of China's agroecosystems by conservation agriculture
Pages 1-12
Rattan Lal
Estimating soil erosion response to land use/cover change in a catchment of the Loess Plateau, China
Pages 13-22
Rui Yan, Xiaoping Zhang, Shengjun Yan, Hao Chen
Factors influencing the adoption of physical soil and water conservation practices in the Ethiopian highlands
Pages 23-30
Asnake Mekuriaw, Andreas Heinimann, Gete Zeleke, Hans Hurni
Evaluation of soil loss estimation using the RUSLE model and SCS-CN method in hillslope mining areas
Pages 31-42
Narayan Kayet, Khanindra Pathak, Abhisek Chakrabarty, Satiprasad Sahoo
Relationships between average gully depths and widths on geological sediments underlying the Idah-Ankpa Plateau of the North Central Nigeria
Pages 43-50
L. Alimonu Oparaku, R. Terungwa Iwar
Impact of urbanization on groundwater recharge and urban water balance for the city of Hyderabad, India
Pages 51-62
Hemant Balwant Wakode, Klaus Baier, Ramakar Jha, Rafig Azzam
Scientific case studies in land-use driven soil erosion in the central United States: Why soil potential and risk concepts should be included in the principles of soil health
Pages 63-78
Benjamin L. Turner, Jay Fuhrer, Melissa Wuellner, Hector M. Menendez, ... Roger Gates
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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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Sustainable intensification of China's agroecosystems by conservation agriculture
Pages 1-12
Rattan Lal
Abstract
Agriculture in China started about 8000 BCE with cultivation of millet and rice. Thus, China's modern agriculture is rooted in a long evolutionary history of agricultural practices. China's population of 211 million in 1700 increased to 295 million in 1800, 400 million in 1900, 1266 million in 2000, and is 1409 million in 2017. Thus, China has to feed 18.5% of the world population on merely 7% of the world's arable land and with even scarcer water resources. Yet, between 1950 and 2017, the grain production in China increased at a faster rate than that of the population. Total grain production (million ton or Tg) was 113 in 1949, 305 in 1970, 462 in 2000, and 603 in 2015. The high agricultural productivity is attributed to high consumption of fertilizers (58.8 Tg in 2015), pesticides (1.81 Tg in 2014), and irrigation (65.7 Mha in 2014). However, the high production is also associated with the severe problems of soil degradation (erosion), water contamination and air pollution. It is estimated that ~40% of China's arable land is degraded to some degree. Thus, there is a strong need for a paradigm shift of sustaining high productivity while restoring quality of natural resources of soil, water and air. In this context, conversion to a system-based conservation agriculture (CA) may be an important strategy of sustainable intensification of agro-ecosystems for advancing and sustaining high production while restoring soil health, purifying water and air and improving the environment. The CA has been practiced in China since 1990s and was adopted on ~8.0 Mha in 2015. The available literature shows that conversion to CA increases soil organic C (SOC) concentration and stocks mostly in the surface layer while also producing an equivalent agronomic yield. Therefore, a widespread adoption of CA in China would necessitate a deeper understanding of its ecological underpinnings. To be effective, site-specific CA practices must reduce risks of soil erosion under dry land farming, achieve and sustain high productivity, reduce emissions of N2O and CH4, sequester SOC, and decrease inputs of fertilizers and pesticides. To be widely accepted, site-specific CA packages must also address the followings: availability of crop residues mulch, techniques of weed control, access to a seed drill, and availability of farm labor. Economically, CA must increase agronomic yield and the farm profit. Being a knowledge-intensive and complex system, there is a strong need to strengthen the extension services, and conduct long-term and farmer-driven research to alleviate specific constraints (e.g., drought, wind and water erosion, nutrient imbalance, weed control).
Estimating soil erosion response to land use/cover change in a catchment of the Loess Plateau, China
Pages 13-22
Rui Yan, Xiaoping Zhang, Shengjun Yan, Hao Chen
Abstract
The vegetation restoration project, named the Grain to Green Program, has been operating for more than ten years in the upper reaches of the Beiluo River basin, located in the Loess Plateau of China. It is significant to be able to estimate the success of preventing soil erosion. In this study, the Revised Universal Soil Loss Equation (RUSLE) and the Sediment Distributed Delivery (SEDD) model were used to assess the annual soil loss derived from water erosion. The results showed that the study area suffered from primary land use changes, with increasing grassland and forest and decreasing farmland from 1990 to 2010. Based on that, the average soil erosion modulus decreased from 18,189.72 t/(km2 a) in 1990–7408.93 t/(km2 a) in 2000 and 2857.76 t/(km2 a) in 2010. Compared with 1990, the average soil erosion modulus decreased by 59.0% and 84.3% for 2000 and 2010, respectively. Benefiting from the increased vegetation coverage and improved ecological environment, the soil erosion in this study area clearly declined. This research also found that the distribution of the three years of soil erosion was similarly based on topographic factors. The soil erosion modulus varied with different land use types and decreased in the order of residential area>farmland>grassland>forest. The average soil erosion modulus gradually increased with the increase of the slope gradient, and 76.08% of the total soil erosion was concentrated in the region with a gradient more than 15 degrees. The soil erosion modulus also varied with slope aspects in the order of sunny slope>half-sunny slope>half-shady slope>shady slope. This research provides useful reference for soil and water conservation and utilization in this area and offers a technical basis for using the RUSLE to estimate soil erosion in the Loess Plateau of China.
Factors influencing the adoption of physical soil and water conservation practices in the Ethiopian highlands
Pages 23-30
Asnake Mekuriaw, Andreas Heinimann, Gete Zeleke, Hans Hurni
Abstract
Soil and Water Conservation (SWC) structures have been constructed on cultivated land for nearly 40 years to reduce soil loss and improve crop yields and people's livelihoods in the Ethiopian highlands. However, the success of this huge effort has been mixed, and the main constraints have not been investigated in detail. This study was undertaken to identify the factors determining the adoption of SWC structures in the Ethiopian Highlands. Case study areas were selected from high-potential and low-potential areas. Data were collected from 269 farmers using face-to-face interviews, and through focus group discussions, key informant interviews and field observations. Binary logistic regression model and descriptive statistics were used to analyze the data. The result showed that the majority (87%) of the farmers interviewed were using SWC structures. Regionally, nearly all farmers in the low-potential areas and 56% of farmers in the high-potential areas constructed and were maintaining the structures properly. This disparity is due to the fact that in the low-potential areas there have been strong governmental involvement and technical and financial support, and hence the farmers there have a better understanding of the multiple uses of physical SWC structures than do farmers in the high-potential areas. In addition, off-farm activities and free grazing plays a substantial role. We can conclude that clear understanding of the benefits of SWC structures by farmers, active involvement and technical support from the government, and genuine participation of farmers in SWC practices were found to be main factors in the adoption of SWC measures.
Evaluation of soil loss estimation using the RUSLE model and SCS-CN method in hillslope mining areas
Pages 31-42
Narayan Kayet, Khanindra Pathak, Abhisek Chakrabarty, Satiprasad Sahoo
Abstract
Mining operations result in the generation of barren land and spoil heaps which are subject to high erosion rate during the rainy season. The present study uses the Revised Universal Soil Loss Equation (RUSLE) and SCS-CN (Soil Conservation Service - Curve Number) process to estimate in Kiruburu and Meghahatuburu mining sites areas. The geospatial model of annual average soil loss rate was determined by integrating environmental variables parameters in a raster pixels-based GIS framework. GIS layers with, rainfall passivity and runoff erosivity (R), soil erodibility (K), slope length and steepness (LS), cover management(C) and conservation practice (P) factors were calculated to determine their effects on annual soil erosion in the study area. The coefficient of determination (r2) was 0.834, which indicates a strong correlation of soil loss with runoff and rainfall. Sub -watersheds 5,9,10 and 2 experienced high level of highly runoff. Average annual soil loss was calculated (30*30 m raster grid cell) to determine the critical soil loss areas (Sub-watershed 9 and 5). Total soil erosion area was classified into five class, slight (10,025 ha), moderate (3125 ha), high (973 ha), very high (260 ha) and severe (53 ha). The resulting map shows greatest soil erosion of >40 t h-1 y-1 (severe) through connection to grassland, degraded and open forestry on the erect mining side-escutcheon. The Landsat pan sharpening image and DGPS survey field data were used in the verification of soil erosion results.
Relationships between average gully depths and widths on geological sediments underlying the Idah-Ankpa Plateau of the North Central Nigeria
Pages 43-50
L. Alimonu Oparaku, R. Terungwa Iwar
Abstract
This study investigated the relationships between the average gully depth and the average width on two of the three geological sediments underlying the Ida-Ankpa Plateau of the North Central Nigeria. Gully length (L), average depth (D), and average width (W) were measured on 37 and 5 gully samples formed respectively on the Ajalli Sandstones’ (AS) and the Upper Coal Measures’ (UCM) geological sediments. From these, the average volume (V), average cross sectional area (A), and average form factor (W/D) were computed. These sets of variables (L, D, W, V, A, and W/D), a total of six for each gully, were analysed using correlation analysis and the sample bivariate regression to examine the relationships between D and W on the two geological units. Results show that D correlates poorly, positively, and significantly with W on the highly erodible AS (R = 0.565, P < 0.01), whereas the relationship is stronger, positive, and significant on the more resistant UCM (R = 0.997, P < 0.01). On the AS, D is a poor predictor of W with the relationship: W1 = 3.670 + 0.355D1 (R2 = 0.319), whereas it is a near-perfect predictor on the UCM (W2 = 1.667 + 0.689D2, R2 = 0.994). The results of the study suggest that for gullies cut on deep, homogeneous formations, the correlation of D with W diminishes with increasing vulnerability to erosion of the sediments, whereas the effectiveness of D as a predictive tool of W increases with the resistance of the sediments to erosion.
Impact of urbanization on groundwater recharge and urban water balance for the city of Hyderabad, India
Pages 51-62
Hemant Balwant Wakode, Klaus Baier, Ramakar Jha, Rafig Azzam
Abstract
Groundwater recharge processes in an urban area are different than in non-urban areas. There are various new components that must be considered in the case of urban groundwater recharge in addition to the natural recharge from precipitation. These various components are estimated in this study based on the water balance equation for the Hyderabad city of India. Initially, urban recharge components including leakages from water supply network and sewage networks were calculated. To estimate the natural recharge from precipitation, actual evapotranspiration and surface runoff were estimated using remote sensing and GIS techniques. Results indicated that the urban recharge component of groundwater was more than ten times greater than the natural recharge. The net urban recharge component of groundwater was estimated to be approximately 568 mm yr-1 and the natural recharge component was observed to be 53 mm yr-1. Water inflow and outflow components were also estimated to provide the complete scenario of the total urban water balance of Hyderabad. This analysis has provided the information regarding the extent and intensity of percolation of urban contaminants into the aquifer.
Scientific case studies in land-use driven soil erosion in the central United States: Why soil potential and risk concepts should be included in the principles of soil health
Pages 63-78
Benjamin L. Turner, Jay Fuhrer, Melissa Wuellner, Hector M. Menendez, ... Roger Gates
Abstract
Despite recent improvements in overall soil health gained through conservation agriculture, which has become a global priority in agricultural systems, soil and water-related externalities (e.g., wind and water erosion) continue to persist or worsen. Using an inductive, systems approach, we tested the hypothesis that such externalities persist due to expansion of cultivation onto areas unsuitable for sustained production. To test this hypothesis, a variety of data sources and analyses were used to uncover the land and water resource dynamics underlying noteworthy cases of soil erosion (either wind or water) and hydrological effects (e.g., flooding, shifting hydrographs) throughout the central United States. Given the evidence, we failed to reject the hypothesis that cultivation expansion is contributing to increased soil and water externalities, since significant increases in cultivation on soils with severe erosion limitations were observed everywhere the externalities were documented. We discuss the case study results in terms of land use incentives (e.g., policy, economic, and biophysical), developing concepts of soil security, and ways to utilize case studies such as those presented to better communicate the value of soil and water resource conservation. Incorporating the tenets of soil potential and soil risk into soil health evaluations and cultivation decision-making is needed to better match the soil resource with land use and help avoid more extreme soil and water-related externalities.