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During periods of no or low crop growth in dryland cropping systems, tillage can reduce residue coverage and thereby elevate wind erosion risk. We measured wind erosion on a silt loam, Haplustoll soil in North Dakota (456 mm precipitation yr–1) in response to levels of tillage applied once in spring during fallow following a small grain–sunflower (Helianthus annuus L.) rotation. Treatments were no‐tillage (NT), one‐pass tandem disk tillage (TDT), and two‐pass offset disk tillage (ODT). Erosion flux was measured with sediment samplers near peripheries of >1‐ha replicated plots from May through September 2003 and 2004. Soil losses in ODT, TDT, and NT were 12.0, 4.8, and 2.1 Mg ha–1, respectively, in 2003 and 2.6, 1.6, and 1.4 Mg ha–1 in 2004. The greatest loss, 12.0 Mg ha–1, was equivalent to 1‐mm soil depth. The two‐ to fivefold greater erosion in 2003, a year with 2 mo of <30% of average precipitation, appears linked to a decline in residue coverage. Coverage remained about the same in NT and increased in tilled treatments during 2004 with more average precipitation. Our measurements of wind erosion have shown how the residue‐destroying effects of a single tillage event can be considerably exacerbated by a moderate, seasonal drought. This indicates the critical importance of NT for limiting soil and residue disturbance and reducing wind erosion risk from drought‐affected plant growth failure in semiarid cropping systems. Core Ideas: Wind erosion loss was two‐ to sixfold greater under disk tillage than no‐tillage.Seasonal drought led to less weed growth and residue coverage.Seasonal drought resulted in two‐ to fivefold greater wind erosion loss.The Revised Wind Erosion Equation (RWEQ) model indicated that residue coverage conferred the greatest resistance to erosion. [ABSTRACT FROM AUTHOR]

Soil C and N have long been recognized as important indicators of soil productivity. The current low levels of soil C and N of cropland soils have led to interest in sequestering C with reduced tillage cropping systems and the Conservation Reserve Program (CRP). Our objective was to assess agroecosystem effects on soft C and N pools in the Southern High Plains. The agroecosystems included three cotton (Gossypium hirsutum L.) cropping systems, CRP land, and native rangeland (NR). We sampled 0- to 5-, 5- to 10-, 10- to 15-, and 15- to 30-cm soil depths at 12 farm sites in five counties in West Texas. Total soil C and N, particulate organic matter (POM) C and N, natural abundance of carbon-13 isotope ([delta][sup.13]C) of POM and of whole soil, potentially mineralizable C and N, water-extractable carbon (WEC), and extractable ammonium (N[H.sup.+.sub.4]) and nitrate (N[O.sup.-.sub.3]) were determined. Total C and N in the 0- to 30-cm soil profile were 34 Mg C [ha.sup.-1] and 2.5 Mg N [ha.sup.-1] for NR, and 23 Mg C [ha.sup.-1] and 1.9 Mg N [ha.sup.-1] for cropland systems, respectively. Total soil C and N in CRP land were greater in cropland soils only in the 0- to 5-cm layer, and were 24 Mg C [ha.sup.-1] and 2.1 Mg N [ha.sup.-1] in 0 to 30 cm. Labile C and N pools were positively correlated with each other and with total soil C and N. Low soft test P may have limited C and N sequestration in CRP land and NR. Improved management practices are needed to sequester C and N in CRP and conservation-tillage cotton systems in the Southern High Plains.

The USDA Natural Resources Conservation Service has proposed the Soil Conditioning Index (SCI) to predict the consequences of management actions on the state of soil organic carbon, a soil quality [...]

The Soil Conditioning index (SCI) and Soil management assessment Framework (SMAF) are two different but complementary methods for evaluating soil quality. Both tools have been widely used, but little is known regarding how they compare and if they provide similar results when the same agricultural management practices are compared. This SCI and SMAF soil quality index (SQI) comparison was conducted on the Fort Cobb Reservoir experimental Watershed (FCREW) in oklahoma. Forty-one loamy and sandy surface soil sites were sampled on the FCREW under (i) annual cropping with conventional tillage (conventional), (ii) annual cropping with either conservation tillage or no-till (conservation), (iii) cropland that had been converted to perennial grass (managed grass), and (iv) native grass. The SCI and SMAF SQI gave similar assessments, indicating that soil quality within conventional and conservation systems was similar but lower than in either managed or native grassland systems. Simple comparisons of soil properties by textural class showed no significant effects on most soil quality indicator values, and although texture by management subgroups was examined, no clear relationships were detected because of the limited number of sampling sites. The SMAF and SCI indicators and scores were correlated in tilled systems with limited vegetative cover but not for no-till or forage-based pasture or grassland systems that were in place for at least 10 yr. The SMAF provided more resolution when evaluating agroecosystem management effects on soil quality, including soil organic C enrichment, especially within forage-based systems. Recognizing that the SMAF currently does not account for soil loss, we conclude with recommendations for improving the tool, particularly for tilled systems. [ABSTRACT FROM AUTHOR]

Soil degradation is one of the most serious ecological problems in the world. In arid and semi-arid northern China, soil degradation predominantly arises from wind erosion. Trends in soil degradation caused by wind erosion in northern China frequently change with human activities and climatic change. To decrease soil loss by wind erosion and enhance local ecosystems, the Chinese government has been encouraging residents to reduce wind-induced soil degradation through a series of national policies and several ecological projects, such as the Natural Forest Protection Program, the National Action Program to Combat Desertification, the "Three Norths" Shelter Forest System, the Beijing-Tianjin Sand Source Control Engineering Project, and the Grain for Green Project. All these were implemented a number of decades ago, and have thus created many land management practices and control techniques across different landscapes. These measures include conservation tillage, windbreak networks, checkerboard barriers, the Non-Watering and Tube-Protecting Planting Technique, afforestation, grassland enclosures, etc. As a result, the aeolian degradation of land has been controlled in many regions of arid and semiarid northern China. However, the challenge of mitigating and further reversing soil degradation caused by wind erosion still remains. [ABSTRACT FROM AUTHOR]

Integrated crop-livestock (ICL) systems that utilize perennial or high-residue no-till annual forages may build soil organic matter and, thus, enhance aggregate stability, water retention, nutrient cycling, and C storage. We examined long-term effects of ICL management on soil organic C (SOC) pools compared with continuous cotton [CTN; (Gossypium hirsutum L.)] at the system and individual vegetation levels, both using limited irrigation (65 and 77% replacement of evapotranspiration, respectively). Soil samples collected in 1997 (baseline) and 2010 were fractionated into four water stable aggregate- size classes: macroaggregate (>250 µm), microaggregate (53-250 µm), and silt + clay (<53 µm), and three intra-aggregate size classes: particulate organic matter (>250 µm), microaggregates (53-250 µm), and silt + clay (<53 µm). Reduced tillage and increased vegetation inputs under WW-B. Dahl Old World bluestem [Bothriochloa bladhii (Retz) S.T. Blake; bluestem], a component of the ICL, resulted in increased mean weight diameter (1.5 mm in bluestem vs. 0.40 mm in CTN) and higher proportions of macroaggregates (59%) than under CTN. A continued increase in SOC was measured in the ICL following 13 yr with 22% more SOC relative to CTN. The results from the detailed soil aggregate C fractionation revealed that an ICL under limited irrigation enhanced SOC stored in protected, recalcitrant aggregate pools (intra-aggregate microaggregate SOC of 8.2 and 5.4 mg g-1 macroaggregate in the ICL and CTN, respectively). These benefits impart important ecosystem services such as potential C sequestration and reduced erosion potential, which are especially important in these semiarid soils. [ABSTRACT FROM AUTHOR]

The article presents a study which measures the bacterial diversity of wind-eroded sediments using a portable field wind tunnel collected from organic-rich soils in Michigan. The study shows that particular bacteria were more predominant in fine dust, such as Firmicutes, Chloroflexi and Bacteriodetes, compared to coarse sediment, such as Acidobacteria and Proteobacteria, revealing various niches and locations of bacteria in soil. Infrared spectroscopy reveals that wind erosion preferentially takes particular types of carbon (C) from the soil that re lost through fine dust.

This study evaluated microbial communities of soil (0-10 cm) as affected by dryland cropping systems under different tillage practices after 5 years. The soil type was an Olton sandy loam with an average of 16.4% clay, 67.6% sand and 0.65 g kg-1 of organic matter (OM). The cropping systems evaluated were grain sorghum (Sorghum bicolor L.)-cotton (Gossypium hirsutum) (Srg-Ct), cotton-winter rye (Secale cereale)-grain sorghum (Ct-Rye-Srg), and a rotation of forage (f) sorghum (Sorghum bicolor L. and Sorghum sudanense) with winter rye (Srf-Rye), which were under no-tillage (nt) and conventional tillage (ct) practices. Soil microbial communities under cotton based cropping systems (Srg-Ct and Ct-Rye-Srg) showed lower fungal:bacterial ratios compared to the soil under Srf-Rye. Soil under Srf-Rye showed higher population densities of Bacteroidetes and Proteobacteria while lower Actinobacteria compared to Srg-Ct and Ct-Rye-Srg. Chloroflexi, Gemmatimonadetes and Verrucomicrobiae were higher in tilled soil compared to the no-tilled plots. Regardless the limited irrigation available to sustain agricultural production within these dryland cropping systems, this study demonstrated that differences in microbial communities are more affected by crop rotation than tillage management history. Although soil fungal diversity was not analyzed in this study, pyrosequencing suggests that tillage practices can affect bacterial phyla distribution in this sandy soil. [ABSTRACT FROM AUTHOR]

The USDA Natural Resources Conservation Service has proposed the Soil Conditioning Index (SCI) to predict the consequences of management actions on the state of soil organic carbon (SOC), a soil quality indicator. The index was developed based on research in humid, temperate, loamy soils but has not been tested for many other conditions. In this project, we determined the effects of management on SCI, SOC, and other soil properties in semiarid, hot, sandy soils located in the Southern High Plains of western Texas. Agroecosystems studied included native rangeland, conservation grassland, cotton (Gossypium hirsutum L.) and wheat (Triticum aestivum L.) rotations, and high-residue forage sorghum (Sorghum bicolor L.). The sites included irrigated and dryland conditions under conventionally tilled and no-tillage practices. Mean SCI values varied from -1.49 for conventionally tilled dryland cotton to 2.15 for the conservation grassland. All native rangelands and conservation grasslands and no-tillage fields (dryland and irrigated) had positive SCI values, which indicates increasing organic matter levels. In contrast, all of the conventionally-tilled cotton fields had negative SCI values, indicating decreasing organic matter levels. The SCI was most strongly correlated with the residue equivalent value (r = 0.68) as estimated in the Revised Universal Soil Loss Equation but based on measured values and particulate organic matter carbon, POM-C (r = 0.57).The SCI showed which fields had the highest levels of POM-C and which fields used no-tillage or limited tillage from fields that had been aggressively tilled. Additional research is needed to adjust the SCI subfactors to better relate the index with SOC. [ABSTRACT FROM AUTHOR]

Abstract: Wind erosion has degraded over one-half billion hectares of land worldwide. 137Cesium (137Cs) has been used as a tracer to study long-term rates of soil redistribution by water and, to a lesser extent, by wind. Early studies assumed that the decline in 137Cs activity for a potentially eroded soil relative to that for an uneroded soil was linearly proportional to soil loss. More recently, models have emerged that consider the effects of soil cultivation and the particle surface area-dependent partitioning of 137Cs on soils. We investigated the partitioning of 137Cs in wind-eroded sediments and with soil surface samples sieved into contiguous ranges of particle sizes. We also compared the 137Cs activities and stratification of several adjacent soils with known wind erosion and deposition histories. Finally, we tested 137Cs-based soil loss models with measured data from sites with documented histories. 137Cs activities and mean particle diameters of aeolian samples agreed well with the 137Cs activities and respective mean diameters of the sieved surface soil samples. Good agreement between model estimations and measured data indicated that 137Cs models developed to estimate soil redistribution by water were also applicable to soil redistribution by wind provided that the models contained an appropriate particle size correction parameter. [Copyright &y& Elsevier]

Wind erosion is a dominant geomorphological process in arid and semi-arid regions with major impacts on regional climate and desertification. The erosion process occurs when the wind speed exceeds a certain threshold value, which depends on a number of factors including surface soil moisture. The understanding and modelling of aeolian erosion requires a better understanding of the soil erodibility associated with different moisture conditions. In arid regions during the dry season, the atmospheric humidity plays an important role in determining the surface moisture content and the threshold shear velocity. By a series of wind tunnel tests and theoretical analyses, this dependence of threshold velocity on near surface air humidity is shown for three soils of different textures: sand, sandy loam, and clay loam. The results show that the threshold shear velocity decreases with increasing values of relative humidity for values of relative humidity between about 40% and 65%, while above and below this range the threshold shear velocity increases with air humidity. A theoretical framework is developed to explain these dependencies assuming an equilibrium between the surface soil moisture and the humidity of the overlying atmosphere. The conditions under which soil-atmosphere equilibrium occurs were tested experimentally in the laboratory for different soils in order to determine the effect of grain surface area and texture on the time required to reach equilibrium starting from different initial conditions. [ABSTRACT FROM AUTHOR]

Abstract: Dusts generated in the laboratory from soils and sediments are used to evaluate the emission intensities, composition, and environmental and health impacts of mineral aerosols. Laboratory dust generation is also utilized in other disciplines including process control and occupational hygiene in manufacturing, inhalation toxicology, environmental health and epidemiology, and pharmaceutics. Many widely available and/or easily obtainable laboratory or commercial appliances can be used to generate mineral aerosols, and several distinct classes of dust generators (fluidization devices, dustfall chambers, rotating drums/tubes) are used for geological particulate studies. Dozens of different devices designed to create dust from soils and sediments under controlled laboratory conditions are documented and described in this paper. When choosing a specific instrument, investigators must consider some important caveats: different classes of dust generators characterize different properties (complete collection of a small puff of aerosol versus sampling of a representative portion of a large aerosol cloud) and physical processes (resuspension of deposited dust versus in situ production of dust). The quantity “dustiness” has been used in industrial and environmental health research; though it has been quantified in different ways by different investigators, it should also be applicable to studies of geological aerosol production. Using standardized dust-production devices and definitions of dustiness will improve comparisons between laboratories and instruments: lessons learned from other disciplines can be used to improve laboratory research on the generation of atmospheric dusts from geological sources. [Copyright &y& Elsevier]