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Drought affects the occurrence and intensity of aeolian dust events in many ecoregions. This study investigated the effects of "drought legacy" (the cumulative temporal persistence of drought's consequences on the earth system) on dust generation, a topic which had not previously been evaluated. We investigated the potential dust/drought legacy relationship in the USA's Southern Great Plains and Chihuahuan Desert ecoregions over 14 years, including the 2011–2012 extreme drought, at spatial distances up to 100 km around dust point sources and for up to 5 years' drought history. At every temporal and spatial scale, drought levels associated with dust initiation points in the two ecoregions were significantly different. Chihuahuan Desert dust sources concentrated in areas of severe to extreme drought, while those in the Southern Great Plains, which experiences greater land use, spanned wider ranges of drought conditions. At short temporal scales of drought (1 week and 1 year), dust initiation in the Chihuahuan Desert was associated strongly with severe to exceptional drought conditions at all spatial extents, while Southern Great Plains dust sources were linked to lower drought intensities. For longer drought histories (the past 2 and 5 years), Chihuahuan Desert dust sources were connected with moderate to severe drought, while Southern Great Plains dust sources were linked to moderate drought, at all spatial extents. Drought's legacies, extending over multiple years and kilometer scales, are shown to have roles in subsequent dust events at regional scales, though they can be regionally modulated by land use practices and ecosystem characteristics. [ABSTRACT FROM AUTHOR]

Arid and semiarid ecosystems around the world are often prone to both soil salinization and accelerated soil erosion by wind. Soil salinization, the accumulation of salts in the shallow portions of the soil profile, is known for its ability to decreases soil fertility and inhibit plant growth. However, the effect of salts on soil erodibility by wind and the associated dust emissions in the early stages of soil salinization (low salinity conditions) remains poorly understood. Here we use wind tunnel tests to detect the effects of soil salinity on the threshold velocity for wind erosion and dust production in dry soils with different textures treated with salt‐enriched water at different concentrations. We find that the threshold velocity for wind erosion increases with soil salinity. We explain this finding as the result of salt‐induced (physical) aggregation and soil crust formation, and the increasing strength of surface soil crust with increasing soil salinity, depending on soil texture. Even though saline soils showed resistance to wind erosion in the absence of abraders, the salt crusts were readily ruptured by saltating sand grains resulting in comparable or sometimes even higher particulate matter emissions compared to non‐saline soils. Interestingly, the salinity of the emitted dust is found to be significantly higher (5–10 times more) than that of the parent soil, suggesting that soil salts are preferentially emitted, and airborne dust is enriched of salts. Plain Language Summary: In this study we investigated how the use of slightly saline irrigation water may affect soil susceptibility to wind erosion and the dust emission potential of dry soils, and how these processes are affected by the amount of clay in the soil. Results indicated that, even though salinity decreased the susceptibility of soils to wind erosion due to aggregation and crust formation, abrasion by sand particles resulted in the breakdown of saline crusts, leading to emissions comparable or sometimes even higher to those of non‐saline soils. The higher salt concentration found in the dust than in the dust‐emitting soil suggests that the airborne transport of salts may have important implications for contaminant transport and salinization of downwind areas. Key Points: Threshold velocities for wind erosion increase with increasing soil salinity because salts induce the formation of a soil crustCrust formation and aggregation can delay dust emission from soil surfaces even under low salinity conditionsSalts are preferentially emitted and amplified in airborne dust [ABSTRACT FROM AUTHOR]

Aeolian sediment transport occurs as a function of, and with feedback to ecosystem changes and disturbances. Many desert grasslands are undergoing rapid changes in vegetation, including the encroachment of woody plants, which alters fire regimes and in turn can change the spatial and temporal patterns of aeolian sediment transport. We investigated aeolian sediment transport and spatial distribution of sediment in the surface soil for 7 years following a prescribed fire using a multiple rare earth element (REE) tracer‐based approach in a shrub‐encroached desert grassland in the northern Chihuahuan desert. Results indicate that even though the aeolian horizontal sediment mass flux increased approximately three‐fold in the first windy season in the burned areas compared to control areas, there were no significant differences after three windy seasons. The soil surface of bare microsites was the major contributor of aeolian sediments in unburned areas (87%), while the shrub microsites contributed the least (<2%) during the observation period. However, after the prescribed fire, the contribution of aeolian sediments from shrub microsites increased considerably (∼40%), indicating post‐fire microsite‐scale sediment redistribution. The findings of this study, which is the first to use multiple REE tracers for multi‐year analysis of the spatial and temporal dynamics of aeolian sediment transport, illustrate how disturbance by prescribed fire can influence aeolian processes and alters dryland soil geomorphology in which distinct soils develop over time at very fine spatial scales of individual plants. Plain Language Summary: In this study, we investigated how soil and nutrients attached to soil particles are transported and redeposited by wind after a prescribed fire using a new tracer method in a desert grassland. Results from this long‐term (7‐years) experiment in a desert grassland in the northern Chihuahuan desert reveal the role of fire in changing the erosional and depositional areas on the soil surface, which in turn determine what vegetation type can dominate the landscape. In a grassland encroached with shrubs, prescribed fire modified soil erosion processes and resulted in a more uniform distribution of nutrients in the landscape, favoring grass recovery. The findings also highlight the role of prescribed fires as an effective grassland management tool. Key Points: First long‐term analysis of post‐fire aeolian sediment transport using multiple rare earth element tracersAeolian transport, fires, and vegetation modify surface processes in which distinct soils develop at very fine spatial scales of individual plantsDemonstrates long‐term changes in the post‐fire shift in aeolian sediment source and sink dynamics in heterogeneous dryland landscapes [ABSTRACT FROM AUTHOR]

Lordsburg Playa, a dry lakebed in the Chihuahuan Desert of southwestern New Mexico (USA), is crossed by Interstate Highway 10 (I-10). Dust from the playa threatens highway safety and has caused dozens of fatal accidents. Two numerical models—the U.S. Department of Agriculture's Single-Event Wind Erosion Evaluation Program (SWEEP) and the American Meteorological Society and U.S. Environmental Protection Agency Regulatory Model (AERMOD)—were used to simulate and predict the generation and dispersion of windblown soil, dust, and PM10 from playa hotspots and estimate PM10 concentrations downwind. SWEEP simulates soil loss and particulate matter emissions from the playa surface, and AERMOD predicts the concentration of transported dust. The modeling was informed by field and laboratory data on Lordsburg Playa's properties, soil and land use/land cover databases, and weather data from meteorological stations. The integrated models predicted that dust plumes originating on the playa—including a large, highly emissive area away from the highway and a smaller, less emissive site directly upwind of the interstate—can lead to hourly average PM10 concentrations of tens, to hundreds of thousands, of micrograms per cubic meter. Modeling results were consistent with observations from webcam photos and visibility records from the meteorological sites. Lordsburg Playa sediment contains metals, as will its dust, but human exposures will be short-term and infrequent. This study was the first to successfully combine the SWEEP wind erosion model and the AERMOD air dispersion model to evaluate PM10 dispersion by wind erosion in a playa environment. With this information, land managers will be able to understand the potential levels of dust and PM10 exposure along the highway, and better manage human health and safety during conditions of blowing dust and sand at Lordsburg Playa. [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.

Many grass‐dominated ecosystems in dryland regions have experienced increasing woody plant density and abundance during the past century. In many cases, this process has led to land degradation and declines in ecosystem functions. An example is the Chihuahuan Desert in the southwestern United States, which experienced different stages of shrub encroachment in the past 150 years. Among a wide variety of mechanisms to explain the grass–shrub transitions in this dryland system, soil erosion (both wind and water) and fire are particularly well studied. Here, we synthesize recent developments on the drivers and feedback in the process of shrub encroachment in the Chihuahuan Desert through the intercomparison of two Long Term Ecological Research (LTER) sites, namely Jornada and Sevilleta. Experimental and modeling studies support a conceptual framework, which underscores the important roles of erosion and fire in woody plant encroachment. Collectively, research at the Jornada LTER provided complementary, quantitative support to the well‐known fertile‐islands framework. Studies at the Sevilleta LTER expanded the framework, adding fire as a major disturbance to woody plants. Conceptual models derived from the synthesis represent the general understanding of shrub encroachment that emerged from research at these two sites, and can guide management interventions aimed at reducing or mitigating undesirable ecosystem state change in many other drylands worldwide. [ABSTRACT FROM AUTHOR]

Abstract: Grasslands, which provide fundamental ecosystem services in many arid and semiarid regions of the world, are undergoing rapid increases in fire activity and are highly susceptible to postfire‐accelerated soil erosion by wind. A quantitative assessment of physical processes that integrates fire‐wind erosion feedbacks is therefore needed relative to vegetation change, soil biogeochemical cycling, air quality, and landscape evolution. We investigated the applicability of a novel tracer technique—the use of multiple rare earth elements (REE)—to quantify soil transport by wind and to identify sources and sinks of wind‐blown sediments in both burned and unburned shrub‐grass transition zone in the Chihuahuan Desert, NM, USA. Results indicate that the horizontal mass flux of wind‐borne sediment increased approximately threefold following the fire. The REE tracer analysis of wind‐borne sediments shows that the source of the horizontal mass flux in the unburned site was derived from bare microsites (88.5%), while in the burned site it was primarily sourced from shrub (42.3%) and bare (39.1%) microsites. Vegetated microsites which were predominantly sinks of aeolian sediments in the unburned areas became sediment sources following the fire. The burned areas showed a spatial homogenization of sediment tracers, highlighting a potential negative feedback on landscape heterogeneity induced by shrub encroachment into grasslands. Though fires are known to increase aeolian sediment transport, accompanying changes in the sources and sinks of wind‐borne sediments may influence biogeochemical cycling and land degradation dynamics. Furthermore, our experiment demonstrated that REEs can be used as reliable tracers for field‐scale aeolian studies. [ABSTRACT FROM AUTHOR]

Soil loss due to wind and water erosion degrades the soil on-site and results in environmental problems due to deposition in off-site areas downstream and downwind of the source field. Wind and water erosion may both occur to varying extents particularly in semi-arid environments. Soil conservation strategies require information about the processes of soil redistribution to mitigate its impact. However, very few studies have partitioned soil erosion between contributions of wind and water. We quantified wind and water erosion on six graded terraces under a uniform crop rotation since 1949 and two tillage management practices begun in 1981. Detailed runoff and sediment yield data have been recorded on all the terraces since 1984. We used a stratified random sampling design to collect soil which were then bulked to form six composites for each terrace. From an adjacent undisturbed native prairie, soil cores were collected and composited similarly to provide a reference. The cores were composited by 15 cm layers in the terraces and, in the reference area, the upper 15 cm layer was subdivided into 5 cm layers and all were measured for 137 Cs activity which was converted to 137 Cs inventory. We then employed an established computer model that equates loss of 137 Cs inventory with soil loss and direct measurement of water-borne sediment loss to estimate 30 year mean wind erosion losses on the terraces by tillage type. We found that no-till management reduced total soil loss by one-third compared with stubble mulch tillage, reduced water-borne sediment loss by about the same amount, and that for both tillage systems, wind erosion was responsible for about 75% of the total soil loss. [ABSTRACT FROM AUTHOR]

Abstract: Wind erosion is increasingly scrutinized as a causative factor in soil degradation and fugitive dust emissions. Although models have been developed to predict wind erosion and dust emissions, they are not accurate in all locations. The temporal and spatial variability of aeolian processes makes local estimates of long-term average erosion costly and time consuming. Atmospheric testing of nuclear weapons during the 1950s and 1960s resulted in anthropogenic radioisotopes that had not previously existed being injected into stratospheric global circulation and subsequently deposited on the Earth’s surface. Many of these radioisotopes are strongly adsorbed to soil particles and their movement on the landscape is a powerful method for investigating soil redistribution by wind, water, and tillage. 137Cs is the most commonly used anthropogenic radioisotope used to assess soil redistribution rates. Models have been developed to equate differences of radioisotope inventories with rates of soil redistribution and these models have been employed globally to assess soil redistribution on agricultural and natural landscapes. The radioisotope method for assessing soil redistribution rates has many advantages, but also a few limitations. One of the major limitations occurs when local sources of radioisotope contamination, particularly 137Cs, mask the pulse from global fallout, making temporal estimates of redistribution difficult or impossible. In this paper, I explore the importance, history, and applications of the radioisotopic technique using 137Cs, particularly as it applies to soil redistribution by wind. [Copyright &y& Elsevier]

Abstract: In the previous paper, the use of soilborne 137Cs from atmospheric fallout to estimate rates of soil redistribution, particularly by wind, was reviewed. This method relies on the assumption that the source of 137Cs in the soil profile is from atmospheric fallout following the period of atmospheric weapons testing so that the temporal and, to a certain extent, the spatial patterns of 137Cs deposition are known. One of the major limitations occurs when local or regional sources of 137Cs contamination mask the pulse from global fallout, making temporal estimates of redistribution difficult or impossible. Like 137Cs, Pu exhibits strong affinity for binding to soil particle surfaces, and therefore, re-distribution of Pu inventory indicates inferred soil re-distribution. Compared to 137Cs, 239Pu and 240Pu offer several important advantages: (a) the two major Pu isotopes have much longer half-lives than 137Cs and (b) the ratio 240Pu/239Pu is used to examine whether the Pu is from stratospheric fallout. In this paper, we review the literature concerning Pu in soil and of current attempts to use this tracer to estimate rates of soil redistribution. We also present preliminary, unpublished data from a pilot study designed to test whether or not 239+240Pu can be used to estimate rates of soil redistribution by wind. Based on similarities of profile distribution and relative inventories between 137Cs measurements and 239+240Pu measurements of split samples from a series of fields with documented wind erosion histories, we conclude that 239+240Pu may well be the anthropogenic radioisotope of choice for future soil redistribution investigations. [Copyright &y& Elsevier]

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.

The article reports on the effects of slope and slope position on local and upstream fluid threshold friction velocities. It states that dunes are common aeolian landforms in deserts. In this study, a computational fluid dynamics (CFD) is employed to simulate a stable wind blowing over slope beds of differing height and coupled with the slope-compensating fluid threshold friction velocity formula. Moreover, based on the CFD model, quantitative analysis of slope gradient and particle position on the initiation of particle movement are performed. Results showed that the slope has a great influence on particle saltation in the windward slope.

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]

Research over the last two decades indicated that a class of plant bioregulators known collectively as substituted tertiary amines (STA) has the potential to increase crop productivity by increasing root growth, photosynthetic efficiency, and overall plant vigor. Although several in vitro and greenhouse studies have been conducted with these materials, few have investigated the efficacy of STA application in commercial production systems. This study was initiated to determine whether STA application on commercially grown paprika (Capsicum annuum L.) would increase yield and pigment Content. Plots were established in producer fields during the 1997 and 1998 growing seasons. Foliar spray treatments of 2-(3,4-dichlorophenoxy) triethylamine (DCPTA) as well as diethyl-2-(4-methylbenzoxy) ethylamine (MBTA) at concentrations of 0, 5, 7, 10, and 15 mg.L-1 were applied to seedlings in 1997 and foliar spray treatments of MBTA at 0. 7, and 10 mg·L-1 were applied to seedlings in 1998. Nested treatments of a plant growth enhancer (PGE) were also applied in 1998. The 7 mg·L-1 MBTA treatment resulted in a 822.2 kg·ha-1 (23.2%) yield increase in 1997 and in a 670.0 kg·ha-1 (27.7%) yield increase in 1998 over untreated controls. The 7 mg·L-1 DCPTA treatments resulted in a 565.6 kg·ha-1 (15.9%) yield increase over untreated controls in 1997. The 1998 PGE treatment resulted in an average 330 kg·ha-1 (12.8%) yield increase. Fruit pigment content was also improved significantly {p < 0.05) by certain STA treatments. STA application appears to be efficacious in commercial production paprika. [ABSTRACT FROM AUTHOR]

Commercially available plant growth regulators (PGR) and plant growth enhancers (PGE) may be used to increase crop productivity and improve fertilizer and water use efficiency. Little independent field-scale research has been conducted concerning the benefit of these materials in actual production systems. This study was initiated to determine the efficacy of foliar PGR and PGE application in the production of paprika and cayenne cultivars of pepper (Capsicum annuum L.). Three PGRs and one PGE were foliarly applied to several production pepper fields in the Pecos River valley of southeastern New Mexico during the 1997 and 1998growing seasons. The Reagan loam (fine-silty, mixed, superactive thermic Ustic Haplocalcid) soils were furrow irrigated with artesian groundwater, and individual replicated treatment blocks were a minimum 0.5 ha in size. All peppers were hand harvested. The paprika peppers were dried to constant weight, yields were determined, and paprika pigment extracts were analyzed spectrometrically. In 1997 and 1998, yield was increased by 15.1 to 24.2% in plants treated with some PGRs. PGE treatment resulted in significant paprika yield increases in 1997 and 1998 and a significant yield increase in cayenne in 1997, but did not have a significant effect on paprika pigment content. The results indicated that foliar application of PGRs and PGEs to pepper cultivars can enhance yields in commercial production fields. [ABSTRACT FROM PUBLISHER]

Driven by erodible soil, hydrological stresses, land use/land cover (LULC) changes, and meteorological parameters, windblown dust events initiated from Lordsburg Playa, New Mexico, United States, threaten public safety and health through low visibility and exposure to dust emissions. Combining optical and radar satellite imagery products can provide invaluable benefits in characterizing surface properties of desert playas—a potent landform for wind erosion. The optical images provide a long-term data record, while radar images can observe land surface irrespective of clouds, darkness, and precipitation. As a home for optical and radar imagery, powerful algorithms, cloud computing infrastructure, and application programming interface applications, Google Earth Engine (GEE) is an invaluable resource facilitating acquisition, processing, and analysis. In this study, the fractional abundance of soil, vegetation, and water endmembers were determined from pixel mixtures using the linear spectral unmixing model in GEE for Lordsburg Playa. For this approach, Landsat 5 and 8 images at 30 m spatial resolution and Sentinel-2 images at 10–20 m spatial resolution were used. Employing the Interferometric Synthetic Aperture Radar (InSAR) techniques, the playa's land surface changes and possible sinks for sediment loading from the surrounding catchment area were identified. In this data recipe, a pair of Sentinel-1 images bracketing a monsoon day with high rainfall and a pair of images representing spring (dry, windy) and monsoon seasons were used. The combination of optical and radar images significantly improved the effort to identify long-term changes in the playa and locations within the playa susceptible to hydrological stresses and LULC changes. The linear spectral unmixing algorithm addressed the limitation of Landsat and Sentinel-2 images related to their moderate spatial resolutions. The application of GEE facilitated the study by minimizing the time required for acquisition, processing, and analysis of images, and storage required for the big satellite data. [ABSTRACT FROM AUTHOR]

Recent observations reveal that dust storms are increasing in the western USA, posing imminent risks to public health, safety, and the economy. Much of the observational evidence has been obtained from ground-based platforms and the visual interpretation of satellite imagery from limited regions. Comprehensive satellite-based observations of long-term aerosol records are still lacking. In an effort to develop such a satellite aerosol dataset, we compared and evaluated the Aerosol Optical Depth (AOD) from Deep Blue (DB) and Dark Target (DT) product collection 6.1 with the Aerosol Robotic Network (AERONET) program in the western USA. We examined the seasonal and monthly average number of Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua DB AOD retrievals per 0.1 ∘ × 0.1 ∘ from January 2003 to December 2017 across the region's different topographic, climatic, and land cover conditions. The number of retrievals in the southwest United States was on average greater than 37 days per 90 days for all seasons except summer. Springtime saw the highest number of AOD retrievals across the southwest, consistent with the peak season for synoptic-scale dust events. The majority of Arizona, New Mexico, and western Texas showed the lowest number of retrievals during the monsoon season. The majority of collocating domains of AOD from the Aqua sensor showed a better correlation with AERONET AOD than AOD from Terra, and the correlation coefficients exhibited large regional variability across the study area. The correlation coefficient between the couplings Aqua DB AOD-AERONET AOD and Terra DB AOD-AERONET AOD ranges from 0.1 to 0.94 and 0.001 to 0.94, respectively. In the majority of the sites that exhibited less than a 0.6 correlation coefficient and few matched data points at the nearest single pixel, the correlations gradually improved when the spatial domain increased to a 50 km × 50 km box averaging domain. In general, the majority of the stations revealed significant correlation between MODIS and AERONET AOD at all spatiotemporal aggregating domains, although MODIS generally overestimated AOD compared to AERONET. However, the correlation coefficient in the southwest United States was the lowest and in stations from a higher latitude was the highest. The difference in the brightness of the land surface and the latitudinal differences in the aerosol inputs from the forest fires and solar zenith angles are some of the factors that manifested the latitudinal correlation differences. [ABSTRACT FROM AUTHOR]

The article offers suggestions for adapting agricultural systems to drought and extreme events. It informs that the draught of the year 2012 in the U.S. possesses clear indication to the climatic changes and it also affected the grain production for corn by reducing it to 13 percent. A map of drought affected area in the U.S. is also presented.

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]

This section describes several conservation projects initiated through the collaboration of China and the U.S. The Grazinglands Research Laboratory, USDA Agricultural Research Service and the Institute of Soil and Water Conservation of the Chinese Academy of Sciences initiated a project in 2005, studied the impact of climate change on soil erosion and crop production in the Loess Plateau of China. Another study used the USDA Annualized Agricultural Nonpoint Source (AnnAGNPS) to develop and apply watershed simulation technology within China. Win erosion mechanics in northern China was the subject of a collaboration between the USDA and the Lanzhou University.