Wind Erosion Risk Research Articles

Detection of Shelterbelt Density Change Using Historic APFO and NAIP Aerial Imagery

Grand Forks County, North Dakota, boasts the highest concentration of shelterbelts in the World. As trees age and reach their lifespan limits, renovations should have taken place with new trees being planted. However, in recent years, the rate of tree removal is thought to exceed the rate of replanting, which can result in a net loss of shelterbelts. Through manual digitization and geographic object-based image analysis (GEOBIA), we mapped shelterbelt densities in the Grand Forks County using historical and contemporary aerial photography, and estimated actual changes in density over 54 years. Our results showed a doubling in shelterbelt densities from 1962 to 2014, with an increase of 6402 m2/km2 over the 52 years (or 123 m2/km2/year). From 2014 to 2016, we measured 1,040,178 m2 of shelterbelt areas removed from the county, creating a density loss of −157 m2/km2/year. The total change over two years was relatively small compared with that seen over the previous 52 years. However, the fact that the rate of shelterbelt planting has slowed, and more removal is occurring, should be of concern for an increased risk of wind erosion, similar to that experienced in Midwestern U.S. during the 1930s. The reduction of shelterbelt density is likely related to changes in farming practices and a decline in the Conservation Reserve Program, resulting from the increased returns of growing other row crops. To encourage shelterbelt planting as a conservation practice, additional guidelines and financial support should be considered to balance the tradeoff between soil erosion and agricultural intensification.

Grazing Crop Residues Has Less Impact in the Short‐Term on Soil Properties than Baling in the Central Great Plains

Core Ideas Corn residue grazing had little to no impact on soil health indicators. Residue baling increased wind erosion risks by 22 to 56%. Baling reduced near‐surface soil water content by 8 to 32%. Soil type or precipitation amount did not influence residue removal impacts on soil properties. Residue grazing can be a more sustainable practice than baling Cattle grazing and baling of corn (Zea mays L.) residues are common practices in integrated crop–livestock systems, but their impacts on soil properties are not well understood on a regional scale. We conducted a 3‐yr study across a precipitation gradient (ranging from 400 to 804 mm) in the central Great Plains to evaluate soil compaction, structural quality, water content, fertility, sorptivity, and microbial biomass in response to corn residue grazing and baling. Six on‐farm sites varying in soil texture, organic matter, crop rotation, and irrigation practices were established with three residue treatments: control, grazing, and baling. Sites were predominantly under conservation tillage management. Residue baling reduced residue cover by 57% and residue grazing by 17% relative to the control. At most sites, residue baling reduced near‐surface soil water content by 8 to 32% and increased wind erodible fraction by 22 to 56% compared with the control but grazing generally had no effect. Residue grazing and baling had small or no negative effects on other measured soil properties regardless of soil type or precipitation amount. When changes in soil properties did occur, they were due to differences in grazing duration or agronomic management. For example, grazing during spring at one of the sites increased soil bulk density by 7% (1.17 vs. 1.26 Mg m−3) relative to the control. This short‐term study indicates that residue grazing, in general, does not impact soil properties, but residue baling at high rates (>50%) could increase wind erosion risks and reduce surface soil water content in this region.

Wind Erosion Risk in Agricultural Soils under Different Tillage Systems in the Middle Anatolia

Today, depending intensive tillage on arid and semi-arid regions, wind erosion is an important environmental problem. Reduced tillage practices are often considered as effective in reducing erosion. In this study, the effects on the wind erosion of different soil tillage applications were examined. Trials were conducted at wind speeds of 13ms-1 in a wind tunnel. After tillage, stubble amount and cover ratio, and mean weighted diameter of soil values were measured. These values were varied from 42.67 to 128 gm-2 for stubble amount, 1.27 to 19.32 % for stubble surface cover ratio and 6.53 to 13.57 mm for mean weighted diameter. At 13 ms-1, sediment transport rates varied from 176 to 1365 gm-2h-1 as depending on different soil tillage. The results showed that the relationships between erosion and shear stress of soil, stubble amount, and mean weighted diameter were found significantly and regression coefficient of relation were R2=0.79, R2=0.95 and R2=0.95 respectively.

Increasing wind erosion resistance of aeolian sandy soil by microbially induced calcium carbonate precipitation

AbstractWind erosion of aeolian sandy soil can cause serious land degradation and other environmental problems, and thus its prevention and control is very important. However, there has not been a very effective way to prevent this severe wind erosion until now, and traditional measures such as mechanical methods, chemical sand‐fixing methods, and agronomic methods also have many disadvantages. The main objective of this study is to evaluate feasibility of microbially induced calcite precipitation (MICP) as a novel soil‐strengthening technique, to cement aeolian sandy soil, and reduce wind erosion risk. For this purpose, aeolian sandy soil was cemented withSporosarcina pasteuriithrough MICP technique, and the physical and mechanical properties and wind erosion resistance of cemented aeolian sandy soil were tested. The results show that wind erosion resistance of aeolian sandy soil can be effectively improved by sprayingS. pasteuriisolution and cementing solution (equal concentration of urea and calcium chloride mixture) into it from the surface, and the cemented aeolian sandy soil had good wind erosion resistance. Finally, morphology of precipitated CaCO3crystals was studied using scanning electron microscope, optical microscope, and X‐ray diffraction. The calcium carbonate crystals produced in aeolian sandy soil were calcite, and the calcium carbonate crystals had polyhedral, spherical, or flower clusters crystal morphology. The results of this study demonstrate an effective way to use MICP technology to cement aeolian sandy soil and prevent wind erosion, and provide a new way for wind erosion prevention.

Effects of low-scale landscape structures on aeolian transport processes on arable land

Abstract The landscape of the semiarid Pampa in central Argentina is characterized by late Pleistocene aeolian deposits, covering large plains with sporadic dune structures. Since the current land use changed from extensive livestock production within the Caldenal forest ecosystem to arable land, the wind erosion risk increased distinctly. We measured wind erosion and deposition patterns at the plot scale and investigated the spatial variability of the erosion processes. The wind-induced mass-transport was measured with 18 Modified Wilson and Cooke samplers (MWAC), installed on a 1.44 ha large field in a 20 × 40 m grid. Physical and chemical soil properties from the upper soil as well as a digital elevation model were recorded in a 20 × 20 m grid. In a 5-month measuring campaign data from seven storms with three different wind directions was obtained. Results show very heterogeneous patterns of erosion and deposition for each storm and indicate favoured erosion on windward and deposits on leeward terrain positions. Furthermore, a multiple regression model was build, explaining up to 70% of the spatial variance of erosion by just using four predictors: topsoil thickness, relative elevation, soil organic carbon content and slope direction. Our findings suggest a structure-process-structure complex where the landscape structure determines the effects of recent wind erosion processes which again slowly influence the structure, leading to a gradual increase of soil heterogeneity.

Particle Size Distribution of Heavy Metals and Magnetic Susceptibility in an Industrial Site.

This study was conducted to explore the relationships between magnetic susceptibility and some soil heavy metals concentrations in various particle sizes in an industrial site, central Iran. Soils were partitioned into five fractions (< 28, 28-75, 75-150, 150-300, and 300-2000µm). Heavy metals concentrations including Zn, Pb, Fe, Cu, Ni and Mn and magnetic susceptibility were determined in bulk soil samples and all fractions in 60 soil samples collected from the depth of 0-5cm. The studied heavy metals except for Pb and Fe displayed a substantial enrichment in the < 28µm. These two elements seemed to be independent of the selected size fractions. Magnetic minerals are specially linked with medium size fractions including 28-75, 75-150 and 150-300µm. The highest correlations were found for < 28µm and heavy metals followed by 150-300µm fraction which are susceptible to wind erosion risk in an arid environment.

Modelling wind-erosion risk in the Laghouat region (Algeria) using geomatics approach

Wind-erosion risk is a challenge that threatens land development in dry-land regions. Soil analysis, remote sensing, climatic, vegetal cover and topographic data were used in a geographic information system (GIS), using multi-criteria analysis (MCA) to map wind-erosion risk (Rwe) in Laghouat, Algeria. The approach was based on modelling the risk and incorporating topographic and climatic effects. The maps were coded according to their sensitivity to wind erosion and to their socio-economic potential, from low to very high. By overlapping the effects of these layers, qualitative maps were drawn to reflect the potential sensitivity to wind erosion per unit area. The results indicated that severe wind erosion affects mainly all the southern parts and some parts in the north of Laghouat, where wind-erosion hazard (Hwe) is very high in 43% of the total area, and which was affected mainly by natural parameters such as soil, topography and wind. The results also identified features vulnerable to Rwe. The product of the hazard and the stake maps indicated the potential risk areas that need preventive measures; this was more than half of the study area, making it essential to undertake environmental management and land-use planning.

Wind Erosion and PM10 Emissions from No‐Tillage Cropping Systems in the Pacific Northwest

Core Ideas Erosion of agricultural lands affect air quality in the Inland Pacific Northwest. Alternatives to tillage‐based cropping systems are needed to reduce wind erosion. No‐tillage cereal cropping systems reduce wind erosion and particulates ≤10 µm in diameter emissions. Economically viable strategies are sought for no‐tillage cropping systems. Wind erosion is a concern in the Inland Pacific Northwest (PNW) of the United States where the emission of particulates ≤10 µm in diameter (PM10) from winter wheat (Triticum aestivum L.)/summer fallow (WW/SF) dryland cropping systems during high winds degrades air quality. There is a potential to reduce the risk of wind erosion using no‐tillage or chemical fallow cropping systems, but wind erosion observations are lacking from these systems. We measured sediment and PM10 flux from reduced‐tillage WW/SF, no‐tillage wheat/chemical fallow (NTW/CF), and no‐tillage spring barley (Hordeum vulgare L.)/spring wheat (NTSB/SW) using a portable wind tunnel near Ralston, WA. Horizontal sediment flux, wind speed, and PM10 concentration were measured over two consecutive 10 min sampling periods inside the tunnel after sowing wheat in spring or late summer on four replications of the rotations. Sediment flux was measured with a modified Bagnold type sampler while wind speed and PM10 concentration were respectively measured with pitot tubes and aerosol monitors positioned at six heights above the soil surface inside the tunnel. Sediment and PM10 fluxes were an order of magnitude greater in late summer than spring. After sowing wheat in spring, sediment and PM10 fluxes were greater for the NTSB/SW than NTW/CF rotation while, after sowing winter wheat in late summer, sediment and PM10 fluxes were greater for the WW/SF than the NTSB/SW rotation. Our results suggest that wind erosion and PM10 emissions can be significantly reduced using no tillage cropping systems in the PNW.

Soil surface cover on irrigated rotations for potato ( Solanum tuberosum L.), dry bean ( Phaseolus vulgaris L.), sugar beet ( Beta vulgaris L.), and soft white spring wheat ( Triticum aestivum L.) in southern Alberta

Soil surface cover (crop residue and fall-seeded cover crops) during the nongrowing season is an important tenet of sustainable agriculture, reducing wind and water erosion risk and enhancing soil water conservation. Expansion of irrigated row crop production, namely, potato (Solanum tuberosum L.), dry bean (Phaseolus vulgaris L.), and sugar beet (Beta vulgaris L.), in southern Alberta in the late 1990s prompted a 12-year (2000 to 2011) study to evaluate rotations and soil management systems for improved soil quality. The study compared conservation (CONS) and conventional (CONV) management systems in three- to six-year rotations. Conservation management included cover crops; reduced tillage; feedlot manure compost addition; and solid-seeded, narrow-row dry bean production. Beginning in the third year of the study (2002), surface residue cover was estimated each spring prior to tillage or seeding. Averaged over 10 years (2002 to 2011), residue cover was significantly higher on CONS (15.6%) versus CONV (7.1%) management. Cover was significantly higher where wheat (Triticum aestivum L.) was the previous crop (33.7%) compared to narrow-row dry bean (9.7%), which was significantly higher than potato and sugar beet (6.5% to 6.7%), which were in turn significantly higher than wide-row bean (3.6%). Inclusion of a fall rye (Secale cereale L.) cover crop after potato or dry bean increased residue cover close to or more than 30%, the threshold required to reduce wind erosion risk. Long-term replacement of cereals with lower residue-producing crops (e.g., potato, dry bean, and sugar beet) on irrigated rotations in southern Alberta should be considered judiciously in light of potential negative effects on surface residue cover.

Integrated spatial assessment of wind erosion risk in Hungary

Abstract. Wind erosion susceptibility of Hungarian soils was mapped on the national level integrating three factors of the complex phenomenon of deflation (physical soil features, wind characteristics, and land use and land cover). Results of wind tunnel experiments on erodibility of representative soil samples were used for the parametrization of a countrywide map of soil texture compiled for the upper 5 cm layer of soil, which resulted in a map representing threshold wind velocity exceedance. Average wind velocity was spatially estimated with 0.5′ resolution using the Meteorological Interpolation based on Surface Homogenised Data Basis (MISH) method elaborated for the spatial interpolation of surface meteorological elements. The probability of threshold wind velocity exceedance was determined based on values predicted by the soil texture map at the grid locations. Ratio values were further interpolated to a finer 1 ha resolution using sand and silt content of the uppermost (0–5 cm) layer of soil as spatial co-variables. Land cover was also taken into account, excluding areas that are not relevant to wind erosion (forests, water bodies, settlements, etc.), to spatially assess the risk of wind erosion. According to the resulting map of wind erosion susceptibility, about 10 % of the total area of Hungary can be identified as susceptible to wind erosion. The map gives more detailed insight into the spatial distribution of wind-affected areas in Hungary compared to previous studies.

Comparison of wind erosion based on measurements and SWEEP simulation: A case study in Kangbao County, Hebei Province, China

Farmland especially dry farmland managed in traditional ways has high wind erosion risk and contributes mainly to dust emission in arid area. Modeling predicting provides a general view to soil erosion susceptibility, and is very helpful for the understanding of potential spatial source of wind erosion. This study applied the Single-event Wind Erosion Evaluation Program (SWEEP) to predict soil wind erosion of farmland in the study area. SWEEP is a standalone version of the erosion sub-model from the Wind Erosion Prediction System (WEPS). It needs fewer calculation parameters than WEPS and is often used for single erosion events of limited size. The objective of this study was to test the feasibility of using SWEEP to estimate annual wind erosion of farmland over large areas (downwind distance >1600m) with limited wind data (2005–2011) from weather stations. We validated the simulation results by comparing them with field measurements and wind tunnel data for the same soils. The soil material eroded by wind included PM10, suspension, saltation, and creep particles. Suspension particles were the main component involved in the soil loss (averaged 61.8%). However, saltation and creep particles dominate the particle clouds for fields with a downwind length of less than 550m (averaged 56.6%), and the mass flux dominated by suspension particles stabilizes when this length is longer than 1000m (averaged 83.4%). PM 10 always has very low proportion (<2.3%). Our validation results suggest that it is feasible to use SWEEP for large areas with limited wind data. However, SWEEP could not simulate the small soil losses that occur especially at low wind velocities well. Many factors contribute to this problem, but the main one is overestimation of the threshold wind velocity. Previous research suggest that it will be difficult to replace SWEEP’s calculation algorithms for the threshold wind velocity, but both these algorithms and some SWEEP parameters must be improved to provide accurate predictions of soil erosion.

Assessing changes in wind erosion climatic erosivity in China’s dryland region during 1961–2012

China’s dryland region has serious wind erosion problem and is sensitive to climate change due to its fragile ecological condition. Wind erosion climatic erosivity is a measure of climatic factors influencing wind erosion, therefore, evaluation of its intensity and response to recent climate changes can contribute to the understanding of climate change effect on wind erosion risk. Using the FAO equation, GIS and statistical analysis tools, this study quantified the climatic erosivity, analyzed its spatiotemporal variations, and detected the trend and sensitivity to climate factors during 1961–2012. The results indicate that mean annual climatic erosivity was 2–166 at 292 stations and 237–471 at 6 stations, with the spatial distribution highly in accordance with wind speed (R2 = 0.94). The climatic erosivity varied greatly over time with the annual variation (CV) of 14.7%–108.9% and monthly variation (concentration degree) of 0.10–0.71 in the region. Meanwhile, annual erosivity showed a significant downward trend at an annual decreasing rate mostly above 1.0%. This significantly decreasing trend was mainly attributed to the obvious decline of wind speed during the period. The results suggest that the recent climate changes were highly possible to induce a decrease of wind erosion risk in China’s dryland region.

Assessment of wind and water erosion risk in the watershed of the Ningxia-Inner Mongolia Reach of the Yellow River, China

The watershed of the Ningxia-Inner Mongolia Reach of the Yellow River (NIMRYR) suffers from soil erosion by wind and water because of the wide distribution of deserts and arsenic sandstones in this region. The sediment generated by erosion fed into the Yellow River directly or by its tributaries, silting up the Yellow River and raising the elevation of the river bed. The silting of the Yellow River result in serious flood disasters in this watershed. Therefore, it is urgent to implement soil conservation projects to control wind and water soil erosion. To reach this objective, understanding the spatial and temporal variations of soil erosion in this watershed is very important. In this study, an assessment of soil erosion risk by wind and water was performed based on soil erosion models. The Integrated Wind Erosion Modeling System (IWEMS) and the Revised Wind Erosion Equation (RWEQ) were used to estimate the wind erosion modulus in this watershed, and the water erosion modulus was estimated by the Revised Universal Soil Loss Equation (RUSLE). The results show that during 2000s, the wind erosion modulus ranged from 0 to 31,440.4t/km2/a, and the water erosion modulus was from 0 to 24,048.5t/km2/a. Moreover, the total soil erosion modulus by wind and water has ranged from 0 to 32,792.7t/km2/a. Due to the influence of regional weather and geomorphology, occurrences of wind and water erosion in this watershed are not identical in their spatial and temporal patterns. Based on the calculated soil erosion modulus, soil erosion risk was assessed according to the “Classification criteria for soil-erosion intensities” (SL190-2007). It was assumed that the areas with erosion intensity higher than slight were at risk of erosion; by this criterion, more than 34% of the total area of the watershed of the NIMRYR would be at erosion risk. Based on this estimation, it was also found that the NIMRYR watershed is not a region of wind–water erosion crisscross and that land-use conversions have a significant impact on soil erosion.

Performance of microbial-induced carbonate precipitation on wind erosion control of sandy soil

Wind erosion is a serious problem throughout the world which results in soil and environment degradation and air pollution. The main objective of this study was to evaluate feasibility of microbial-induced carbonate precipitation, as a novel soil-strengthening technique, to reduce wind erosion risk of a sandy soil. For this purpose, the erosion of biocemented soil samples was investigated experimentally in a wind tunnel under the condition of wind velocity of 45 km h−1. The weight loss of treated samples relative to the weight loss of control treatment was 1.29 and 0.16 % for low and high bacterial mix concentrations, respectively, indicating a significant improvement in erosion control in biologically treated samples. The effect of biological treatment on wind erosion control was even superior at the higher velocities. Thereafter, the penetration resistance of the surface layers as a simple index of resistance against wind erosion was measured. Significant improvements in the penetration resistance of the treated soil samples were observed. Although low bacterial mix concentrations did not significantly improve the penetration resistance of the samples, significant improvements in the penetration resistance of the treated soil samples were observed reaching to the highest measured strength (56 kPa) in high bacterial mix concentrations samples. Finally, the morphology of precipitated CaCO3 crystals using scanning electron microscopy and X-ray powder diffraction analysis showed that the CaCO3 was mainly precipitated as vaterite crystals forming point-to-point contacts between the sand granules.

Implications of climate change on wind erosion of agricultural lands in the Columbia plateau

Climate change may impact soil health and productivity as a result of accelerated or decelerated rates of erosion. Previous studies suggest a greater risk of wind erosion on arid and semi-arid lands due to loss of biomass under a future warmer climate. There have been no studies conducted to assess the impact of climate change on wind erosion in the Columbia Plateau of the Pacific Northwest United States where wind erosion of agricultural lands can cause exceedance of national air quality standards. The Wind Erosion Prediction System (WEPS) was used to assess wind erosion and PM10 (particulate matter ≤10µm in aerodynamic diameter) emissions under a future climate projected by downscaling 18 Global Climate Models (GCM) for a conservative emissions pathway. Wind erosion simulations were conducted at Lacrosse and Lind, WA and Moro, OR on a winter wheat-summer fallow (WW-SF) rotation and at Lind on an additional winter wheat-camelina-summer fallow (WW-Cam-SF) rotation. Each rotation was subject to conservation or conventional tillage practices for a baseline (1970–1999) and mid-21st century climate (2035–2064). A significant increase in temperature and nominal increases in precipitation were projected by an ensemble of climate models for the Columbia Plateau by the mid-21st century. Soil and PM10 losses were 25–84% lower for a mid-21st century climate, due in part to greater biomass production associated with CO2 fertilization and warmer temperatures. The reduction in soil and PM10 loss is projected to be more apparent for conservation tillage practices in the future. Soil and PM10 losses were greater from a WW-Cam-SF rotation than WW-SF rotation when conservation tillage practices were employed during the fallow phase of the rotations. Despite accounting for differences in the length of each rotation, annual soil and PM10 losses remained higher for the WW-Cam-SF rotation than the WW-SF rotation. Soil and PM10 losses were more variable across years during 1970–1999 than 2035–2064; however, small and inconsistent differences in the coefficient of variation in soil loss between 1970–1999 and 2035–2064 suggest similarity in climate extremes which govern wind erosion.

Twelve Years of Stover Removal Increases Soil Erosion Potential without Impacting Yield

Corn (Zea mays L.) stover (non-grain aboveground biomass) in the US Corn Belt is used increasingly for livestock grazing and co-feed and for cellulosic bioenergy production. Continuous stover removal, however, could alter long-term agricultural productivity by affecting soil organic C (SOC) and soil physical properties, indicators of soil fertility and erosion potential. In this study, we showed that 12 consecutive yr of 55% stover removal did not affect mean grain yields at any N fertilizer rate (4.5, 6.3, and 6.0 Mg ha−1 for 60, 120, and 180 kg N ha−1 yr−1, respectively) in a marginally productive, rainfed continuous corn system under no-till (NT). Although SOC increased in the top 30 cm of all soils since 1998 (0.54–0.79 Mg C ha−1 yr−1), stover removal tended to limit SOC gains compared with no removal. Near-surface soils (0–5-cm depth) were more sensitive to stover removal and showed a 41% decrease in particulate organic matter stocks, smaller mean weight diameter of dry soil aggregates, and lower abundance of water-stable soil aggregates compared with soils with no stover removal. Increasing N fertilizer rate mitigated losses in total water-stable aggregates in near-surface soils related to stover removal. Collectively, however, our results indicated soil structure losses in surface soils due to lower C inputs. Despite no effect on crop yields and overall SOC gains with time using NT management, annually removing stover for 12 yr resulted in a higher risk of wind and water erosion at this NT continuous corn site in the western Corn Belt.

A universal meteorological method to identify potential risk of wind erosion on heavy-textured soils

Abstract The climate of Central Europe, mainly winter seasons with no snow cover at lower altitudes and a spring drought as well, might cause erosion events on heavy-textured soils. The aim of this paper is to define a universal method to identify the potential risk of wind erosion on heavy-textured soils. The categorization of potential wind erosion risk due to meteorological conditions is based on: (i) an evaluation of the number of freeze-thaw episodes forming bare soil surfaces during the cold period of year; and (ii), an evaluation of the number of days with wet soil surfaces during the cold period of year. In the period 2001–2012 (from November to March), episodes with temperature changes from positive to negative and vice versa (thaw-freeze and freeze-thaw cycles) and the effects of wet soil surfaces in connection with aggregate disintegration, are identified. The data are spatially interpolated by GIS tools for areas in the Czech Republic with heavy-textured soils. Blending critical categories is used to locate potential risks. The level of risk is divided into six classes. Those areas identified as potentially most vulnerable are the same localities where the highest number of erosive episodes on heavy-textured soils was documented.

Assessment of wind-erosion risk in the watershed of the Ningxia-Inner Mongolia Reach of the Yellow River, northern China

Abstract The watershed of the Ningxia-Inner Mongolia Reach of the Yellow River (NIMRYR) suffers from serious wind-erosion hazard from several deserts distributed in this watershed. A mass of aeolian sediment is fed into the Yellow River directly or by its tributaries, which clogs the channel and causes major disasters in local regions. To prevent siltation of the Yellow River, it is urgent to understand the spatial variability and patterns of wind erosion in the NIMRYR watershed. For this purpose, the Integrated Wind-Erosion Modelling System (IWEMS) and the Revised Wind-Erosion Equation (RWEQ) were used to estimate the potential wind erosion rate (PWER) and to map wind-erosion risk in this watershed. In this study, the IWEMS model was used to calculate the PWER in non-arable lands, and the PWER in arable lands was estimated by the RWEQ model. The results show that the average PWER in the NIMRYR watershed ranged between 0 and 31440.4 t/km 2 /a from 2001 to 2010. The areas with tolerable erosion, slight erosion, moderate erosion, severe erosion, very severe erosion, and destructive erosion occupied 31.04%, 38.13%, 22.89%, 6.46%, 0.93%, and 0.55% of the total watershed area, respectively. The assessment results showed that sandy lands have the highest wind-erosion risk and that the risk in arable lands is lowest. The average annual quantity of aeolian sediment blown into the NIMRYR was 15.87 Mt between 2001 and 2010, and that blown into the Ten Tributaries was 7.33 Mt.

Soil coverage evolution and wind erosion risk on summer crops under contrasting tillage systems

Fil: Mendez, Mariano Javier. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Instituto de Ciencias de la Tierra y Ambientales de La Pampa. Universidad Nacional de La Pampa. Facultad de Ciencias Exactas y Naturales. Instituto de Ciencias de la Tierra y Ambientales de La Pampa; Argentina

Management options for water-repellent soils in Australian dryland agriculture

Water-repellent (‘non-wetting’) soils are a major constraint to agricultural production in southern and south-west Australia, affecting &gt;10 Mha of arable sandy soils. The major symptom is dry patches of surface soil, even after substantial rainfall, directly affecting agricultural production through uneven crop and pasture germination, and reduced nutrient availability. In addition, staggered weed germination impedes effective weed control, and delayed crop and pasture germination increases the risk of wind erosion. Water repellency is caused by waxy organic compounds derived from the breakdown of organic matter mostly of plant origin. It is more prevalent in soils with a sandy surface texture; their low particle surface area : volume ratio means that a smaller amount of waxy organic compounds can effectively cover a greater proportion of the particle surface area than in a fine-textured soil. Water repellency commonly occurs in sandy duplex soils (Sodosols and Chromosols) and deep sandy soils (Tenosols) but can also occur in Calcarosols, Kurosols and Podosols that have a sandy surface texture. Severity of water repellency has intensified in some areas with the adoption of no-till farming, which leads to the accumulation of soil organic matter (and hence waxy compounds) at the soil surface. Growers have also noticed worsening repellency after ‘dry’ or early sowing when break-of-season rains have been unreliable. Management strategies for water repellency fall into three categories: (i) amelioration, the properties of surface soils are changed; (ii) mitigation, water repellency is managed to allow crop and pasture production; (iii) avoidance, severely affected or poorly producing areas are removed from annual production and sown to perennial forage. Amelioration techniques include claying, deep cultivation with tools such as rotary spaders, or one-off soil inversion with mouldboard ploughs. These techniques can be expensive, but produce substantial, long-lasting benefits. However, they carry significant environmental risks if not adopted correctly. Mitigation strategies include furrow-seeding, application of wetting agents (surfactants), no-till with stubble retention, on-row seeding, and stimulating natural microbial degradation of waxy compounds. These are much cheaper than amelioration strategies, but have smaller and sometimes inconsistent impacts on crop production. For any given farm, economic analysis suggests that small patches of water repellency might best be ameliorated, but large areas should be treated initially with mitigation strategies. Further research is required to determine the long-term impacts of cultivation treatments, seeding systems and chemical and biological amendments on the expression and management of water repellency in an agricultural context.