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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]

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]

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.

Estimation of mean water status in a field is crucial to effective irrigation water management. Problems encountered with the estimation of mean field soil water status may be attributed to spatial variability of soil physical properties. Several investigators have shown temporal stability of spatial patterns of field measured soil water content, but temporal stability of field measured soil matric potential ([[Psi].sub.m]), a measure of soil water status more appropriate for irrigation scheduling, has not previously been reported to last for more than a few days within one irrigation cycle. This study investigated the temporal stability of spatial patterns of [[Psi].sub.m] both within and between sequential irrigation cycles. Sixty locations in a 1-ha field were outfitted with a 1-m neutron probe access tube and three tensiometers placed at 0.15-, 0.3-, and 0.5-m depths. The observations obtained from 14 d of soil water content measurements and 46 d of [[Psi].sub.m] measurements within eight irrigation cycles were analyzed with Spearman's rank correlation coefficients and a relative differencing technique. The results showed temporally stable soil water content spatial patterns and also indicated temporally stable [[Psi].sub.m] spatial patterns if assumptions of full soil wetting at the beginning of the cycle and uniform evapotranspiration among locations were satisfied. Several locations in the field estimated the field mean [[Psi].sub.m] to within 10% within a given range of potentials, and a few estimated the field mean to within 20% across the entire range of potentials tested. Other locations estimated the lower and higher percentiles of [[Psi].sub.m] with similar accuracy.

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]