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The effect tree species have on soil organic carbon (SOC) has been hotly debated but, so far, few clear patterns have emerged. One example of a differing tree species effect on SOC are aspen forests in North America, which have been found... more
The effect tree species have on soil organic carbon (SOC) has been hotly debated but, so far, few clear patterns have emerged. One example of a differing tree species effect on SOC are aspen forests in North America, which have been found to have more stable SOC than adjacent conifer forest stands. An important source for the formation of stable organo-mineral complexes in soil is dissolved organic carbon (DOC). DOC concentrations in mineral soil are often higher under the thick O-horizons of conifer forests than under aspen forests, but this does not correspond to more stable mineral SOC. This suggests that, instead of DOC concentration, DOC quality could be driving the observed differences in SOC. Therefore, we quantified the retention of contrasting forest detritus DOC in soils. Using a batch sorption experiment approach, we compared the retention of detritus leachates from four sources – aspen leaves (AL), aspen roots (AR), conifer (subalpine fir) needles (CN), and conifer (suba...
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Dissolved organic carbon concentration from soil management, root exudates, and root-colonizing bacteria is dominant over the effect of pH in determining dissolved Cu concentration from CuO nanoparticles at alkaline pH.
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Figure 3. Only compost additions at 25 Mg/ha or higher significantly increased the soil microbial biomass carbon. Adding feather meal with the compost did not significantly increase microbial biomass C relative to the compost amendment.... more
Figure 3. Only compost additions at 25 Mg/ha or higher significantly increased the soil microbial biomass carbon. Adding feather meal with the compost did not significantly increase microbial biomass C relative to the compost amendment. Figure 4. The amount of mineralizable organic carbon increased with the rate of compost applied. It was not significantly affected by the addition of chicken manure or feather meal.
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Abstract Selenium (Se) has potentially deleterious impacts on flora and fauna of aquatic ecosystems. As Se moves through a wetlands system, various processes such as sorption onto sediments, plant uptake, and volatilization into the... more
Abstract Selenium (Se) has potentially deleterious impacts on flora and fauna of aquatic ecosystems. As Se moves through a wetlands system, various processes such as sorption onto sediments, plant uptake, and volatilization into the atmosphere can attenuate Se resulting in its storage in the wetlands. A comparison of inlet and outlet Se fluxes can be used to determine the mass of Se stored in a wetlands system. Inlet and outlet total Se concentrations and water discharge were measured at the Pariette Wetlands, UT, and used to calculate Se fluxes. The difference between inputs and outputs or fluxes gave great insight into how much Se was being retained or stored in the wetlands. The average influx of Se was 1530 kg year−1 and outflux was 380 kg year−1. On average, 75% (1150 kg year−1) of Se entering the wetlands was retained or stored by some biogeochemical process. Processes associated with Se retention included bioaccumulation into the biota, volatilization by plants and sediments, precipitation of insoluble phases, and sorption to sediments, which accounted for most of the attenuated Se. Water movement through the Pariette Wetlands system did not appreciably alter annual Se attenuation rates. Input, output, storage, and fate of Se for four other wetlands were compared with Pariette Wetlands with Se storage being similar among three of the wetlands: Tulare Lake (65%), Imperial (46%), Brawley (72%), and Pariette (75%).
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Cost-effective "green" methods of producing Ag nanoparticles (NPs) are being examined because of the potential of these NPs as antimicrobials. Ag NPs were generated from Ag ions using extracellular metabolites from a soil-borne... more
Cost-effective "green" methods of producing Ag nanoparticles (NPs) are being examined because of the potential of these NPs as antimicrobials. Ag NPs were generated from Ag ions using extracellular metabolites from a soil-borne Pythium species. The NPs were variable in size, but had one dimension less than 50 nm and were biocoated; aggregation and coating changed with acetone precipitation. They had dose-dependent lethal effects on a soil pseudomonad, Pseudomonas chlororaphis O6, and were about 30-fold more effective than Ag(+) ions. A role of reactive oxygen species in cell death was demonstrated by use of fluorescent dyes responsive to superoxide anion and peroxide accumulation. Also mutants of the pseudomonad, defective in enzymes that protect against oxidative stress, were more sensitive than the wild type strain; mutant sensitivity differed between exposure to Ag NPs and Ag(+) ions demonstrating a nano-effect. Imaging of bacterial cells treated with the biocoated Ag N...
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Interactions of neutral and cationic spin probes with a smectite and a smectite-humic acid complex. M Spagnuolo, P Baveye, A Jacobson, MDR Pizzigallo, P Ruggiero Fresenius Environmental Bulletin 13:1111, 1344-1349, 2004. ...
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III. Results Ques%on: What happens when wheat plants, grown with a beneficial microbe, PcO6, are exposed to CuO NPs? Findings: Growth • LiEle variaTon in shoot growth between treatments (Fig. 3). • Plants with PcO6 colonizaTon retained... more
III. Results Ques%on: What happens when wheat plants, grown with a beneficial microbe, PcO6, are exposed to CuO NPs? Findings: Growth • LiEle variaTon in shoot growth between treatments (Fig. 3). • Plants with PcO6 colonizaTon retained NP-‐ inhibiTon of root growth (Fig. 3). Increased lignificaTon in specific cells • Control leaves show lignificaTon in vascular bundles (Fig.4). With addiTon of Cu from CuO NPs, lignificaTon of sclerenchyma cells increased. IV. Conclusions • CuO NPs increased lignificaTon in sclerenchyma cells of the leaves of wheat colonized by PcO6. • Sclerenchyma provides strength and support to the plant [6]. This induced lignificaTon may explain increased sTffness of wheat shoots when grown with CuO NPs.
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Strategies to reduce crop losses due to drought are needed as climate variability affects agricultural productivity. Wheat (Triticum aestivum var. Juniper) growth in a nutrient-sufficient, solid growth matrix containing varied doses of... more
Strategies to reduce crop losses due to drought are needed as climate variability affects agricultural productivity. Wheat (Triticum aestivum var. Juniper) growth in a nutrient-sufficient, solid growth matrix containing varied doses of CuO, ZnO, and SiO2 nanoparticles (NPs) was used to evaluate NP mitigation of drought stress. NP amendments were at fertilizer levels, with maxima of 30 Cu, 20 Zn, and 200 Si (mg metal/kg matrix). Seeds of this drought-tolerant cultivar were inoculated with Pseudomonas chlororaphis O6 (PcO6) to provide a protective root microbiome. An 8 day drought imposed on 14 day-old wheat seedlings decreased shoot and root mass, shoot water content, and the quantum yield of photosystem II when compared to watered plants. PcO6 root colonization was not impaired by drought or NPs. A dose-dependent increase in the Cu, Zn, and Si from the NPs was observed from analysis of the rhizosphere solution, and this process was not affected by drought. Consequently, fertilizer concentrations of the NPs did not further improve drought tolerance in wheat seedlings under the growth conditions of adequate mineral nutrition and the presence of a beneficial microbiome. These findings suggest that potential NP benefits in promoting plant drought tolerance occur only under certain environmental conditions.
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Abstract Colonization of certain probiotic microbes as a biofilm on plant roots induces beneficial responses that boost plant health. The surface colonization, biofilm formation, and production of ...
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Formulations that include nanoparticles of CuO and ZnO are being considered for agricultural applications as fertilizers because they act as sources of Cu or Zn. Currently, few studies of the effects of these nanoparticles (NPs) consider... more
Formulations that include nanoparticles of CuO and ZnO are being considered for agricultural applications as fertilizers because they act as sources of Cu or Zn. Currently, few studies of the effects of these nanoparticles (NPs) consider the three-way interactions of NPs with the plant plus its microbiome. At doses that produced root shortening by both nanoparticles (NPs), CuO NPs induced the proliferation of elongated root hairs close to the root tip, and ZnO NPs increased lateral root formation in wheat seedlings (Triticum aestivum L.). These responses occurred with roots colonized by a beneficial bacterium, Pseudomonas chlororaphis O6 (PcO6), originally isolated from roots of wheat grown under dryland farming in calcareous soils. The PcO6-induced tolerance to drought stress in wheat seedlings was not impaired by the NPs. Rather, growth of the PcO6-colonized plants with NPs resulted in systemic increases in the expression of genes associated with tolerance to water stress. Increas...
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The impact of copper oxide nanoparticles (CuONPs) on crop production is dependent on the biogeochemistry of Cu in the rooting zone of the plant. The present study addressed the metabolites in wheat root exudates that increased dissolution... more
The impact of copper oxide nanoparticles (CuONPs) on crop production is dependent on the biogeochemistry of Cu in the rooting zone of the plant. The present study addressed the metabolites in wheat root exudates that increased dissolution of CuONPs and whether solubility correlated with Cu uptake into the plant. Bread wheat (Triticum aestivum cv. Dolores) was grown for 10 d with 0 to 300 mg Cu/kg as CuONPs in sand, a matrix deficient in Fe, Zn, Mn, and Cu for optimum plant growth. Increased NP doses enhanced root exudation, including the Cu-complexing phytosiderophore, 2'-deoxymugineic acid (DMA), and corresponded to greater dissolution of the CuONPs. Toxicity, observed as reduced root elongation, was attributable to a combination of CuONPs and dissolved Cu complexes. Geochemical modeling predicted that the majority of the solution phase Cu was complexed with citrate at low dosing or DMA at higher dosing. Altered biogeochemistry within the rhizosphere correlated with bio-respons...
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Nanoparticle (NPs) containing essential metals are being considered in formulations of fertilizers to boost plant nutrition in soils with low metal bioavailability. This paper addresses whether colonization of wheat roots by the... more
Nanoparticle (NPs) containing essential metals are being considered in formulations of fertilizers to boost plant nutrition in soils with low metal bioavailability. This paper addresses whether colonization of wheat roots by the bacterium, Pseudomonas chlororaphis O6 (PcO6), protected roots from the reduced elongation caused by CuO NPs. There was a trend for slightly elongated roots when seedlings with roots colonized by PcO6 were grown with CuO NPs; the density of bacterial cells on the root surface was not altered by the NPs. Accumulations of reactive oxygen species in the plant root cells caused by CuO NPs were little affected by root colonization. However, bacterial colonization did reduce the extent of expression of an array of genes associated with plant responses to stress induced by root exposure to CuO NPs. PcO6 colonization also reduced the levels of two important chelators of Cu ions, citric and malic acids, in the rhizosphere solution; presumably because these acids were...
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Abstract The basin-fill aquifers of the Western U.S. contain elevated concentrations of arsenic in the groundwater due to ancient volcanic deposits that host arsenic minerals. Microcosms were constructed using two oxidized sediments and,... more
Abstract The basin-fill aquifers of the Western U.S. contain elevated concentrations of arsenic in the groundwater due to ancient volcanic deposits that host arsenic minerals. Microcosms were constructed using two oxidized sediments and, by contrast, a reduced sediment collected from a shallow basin-fill aquifer in the Cache Valley Basin, Northern Utah to evaluate the fate of geologic arsenic under anoxic conditions. Sequential extractions indicated the primary arsenic host mineral was amorphous iron oxides, but 13%–17% of the total arsenic was associated with carbonate minerals. Arsenic was solubilized from the sediments when incubated with groundwater in the presence of native organic carbon. Arsenic solubilization occurred prior to iron reduction rather than the commonly observed co-reactivity. Arsenic(V) associated with carbonate minerals was the main source of arsenic released to solution and redistributed onto less soluble minerals, including FeS and siderite as defined by chemical extraction. Arsenic reduction occurred only in the site-oxidized sediments. The addition of a carbon and energy source, glucose, resulted in enhanced arsenic solubilization, which was coupled with iron reduction from the site-oxidized sediments. Adding glucose promoted iron reduction that masked the role of carbonate minerals in arsenic solubilization and retention as observed with incubation with groundwater only.
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Abstract Elevated arsenic concentrations have been reported in groundwater samples collected from the semi-arid Western U.S., including the Cache Valley Basin, Utah. The volcanic rock in the basin-fill aquifers underlying portions of the... more
Abstract Elevated arsenic concentrations have been reported in groundwater samples collected from the semi-arid Western U.S., including the Cache Valley Basin, Utah. The volcanic rock in the basin-fill aquifers underlying portions of the West is considered the primary source of arsenic, but there is debate about the mechanisms that control arsenic solubilization in these semi-arid and arid climates. Sediment cores were collected from a shallow basin fill aquifer in the Cache Valley Basin to systematically determine arsenic mineralogy and solubilization mechanisms in relation to non-redox and redox induced soil processes. Soluble arsenic was present throughout the two studied profiles in varying abundance and oxidation state, with the highest concentration of soluble As(V) and As(III) at the depth of the water table. Sequential chemical extractions of arsenic, with oxidation preservation strategies, revealed mineral sources and sinks of arsenic vulnerable to altering redox conditions down the profile. Weathering of primary arsenic-bearing minerals resulted in soluble arsenic in the vadose zone. Once soluble arsenic was leached to the deeper profile, arsenic solubility was controlled by carbonate minerals that concentrate at the water table. In the zone with alternating oxidizing and reducing conditions, iron oxides became the controlling mineral phase. The association between arsenic and sulfides limited arsenic solubility at depths under permanent water saturation. Arsenic solubility was revealed to be controlled by a sequence of processes that prevail under different geochemical regimes down the profile.
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A recent water quality report recognized concentrations of salts and selenium above total maximum daily loads (TMDLs) in the Pariette Wetlands located in the Uintah Basin, Utah. Since the wetlands are located in the Pacific Migratory... more
A recent water quality report recognized concentrations of salts and selenium above total maximum daily loads (TMDLs) in the Pariette Wetlands located in the Uintah Basin, Utah. Since the wetlands are located in the Pacific Migratory Flyway and frequented by numerous water fowl, the elevated levels of total dissolved solids and Se are of concern. To determine whether it possible to manage the mobilization of salts and associated contaminants through the watershed soils into the Pariette Wetlands, knowledge of the spatio-temporal dynamics and distribution of these contaminants is required. Thus, the objective of this study is to characterize the spatio-temporal mobilization of salts and total selenium in the Pariette Draw watershed. Intensive soil information is being collected along the streams feeding the wetlands from fields representing the dominant land-uses in the watershed (irrigated agricultural fields, fallow salt-crusted fields, oil and natural gas extraction fields) using ...
Transport of the pathogenic protozoan Cryptosporidium parvum through soils threatens ground and surface wather. C. parvum may be introduced into soils in the maure of infected calves. The presences of other chemicals in the soil applied... more
Transport of the pathogenic protozoan Cryptosporidium parvum through soils threatens ground and surface wather. C. parvum may be introduced into soils in the maure of infected calves. The presences of other chemicals in the soil applied as or with amendments may affect the transport of the C. parvum oocysts. Surfactants, in particular, which are used in many herbicide formulations, decrease water tension and may disrupt the air-water interface where oocysts are thought to accumulate. We investigate the effect of the anionic surfactant Aerosol-80 on the transport of C. parvum oocysts through four agricultural soils from Utah and Illinois. We find that the presence of the surfactant accelerated the transport of the oocysts through preferential flow paths. On the otherhand, when connected macropores were not present in the soils, the presence of the surfactant retarded the transport of the oocysts through the soil matrix by straining oocyst-surfactant-Ca flocs.
Quaking aspen (Populus tremuloides) is an iconic component in the western landscape that is threatened by conifer encroachment. Prior studies in Northern Utah have shown that mineral soils under aspen forest contain significantly more... more
Quaking aspen (Populus tremuloides) is an iconic component in the western landscape that is threatened by conifer encroachment. Prior studies in Northern Utah have shown that mineral soils under aspen forest contain significantly more soil organic carbon (SOC) than soils under adjacent conifer forests, and that despite rapid turnover of aspen litter, SOC in the upper mineral soil under aspen is more stable and less decomposable. Thus there is great concern about the impact of conifer encroachment on the ecosystem carbon balance. To better understand the amount and character of the SOC changes that result from conifer invasion of aspen stands, mineral soil samples (0-15cm) were collected in paired plots and along transects across pure and mixed aspen and conifer stands at three locations in Northern Utah. Soils were separated using size-density fractionation and analyzed spectrometrically in the mid- (MIR: 250-4000 cm-1) and near-infrared (NIR: 4000-11000 cm-1) ranges to provide insi...
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Zn is an essential element for plants yet some soils are Zn-deficient and/or have low Zn-bioavailability. This paper addresses the feasibility of using ZnO nanoparticles (NPs) as soil amendments to improve Zn levels in the plant. The... more
Zn is an essential element for plants yet some soils are Zn-deficient and/or have low Zn-bioavailability. This paper addresses the feasibility of using ZnO nanoparticles (NPs) as soil amendments to improve Zn levels in the plant. The effects of soil properties on phytotoxicity and Zn bioavailability from the NPs were studied by using an acidic and a calcareous alkaline soil. In the acid soil, the ZnO NPs caused dose-dependent phytotoxicity, observed as inhibition of elongation of roots of wheat, Triticum aestivum. Phytotoxicity was mitigated in the calcareous alkaline soil although uptake of Zn from the ZnO NPs occurred doubling the Zn level compared to control plants. This increase occurred with a low level of Zn in the soil solution as expected from the interactions of Zn with the soil components at the alkaline pH. Soluble Zn in the acid soil was 200-fold higher and shoot levels were tenfold higher than from the alkaline soil correlating with phytotoxicity. Mitigation of toxicity was not observed in plants grown in sand amended with a commercial preparation of humic acid: growth, shoot uptake and solubility of Zn from the NPs was not altered by the humic acid. Thus, variation in humic acid between soils may not be a major factor influencing plant responses to the NPs. These findings illustrate that formulations of ZnO NPs to be used as a soil amendment would need to be tuned to soil properties to avoid phytotoxicity yet provide increased Zn accumulations in the plant.
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In a wild fire, organic volatile compounds from vegetation condense on soil particles forming a hydrophobic layer several centimeters below the soil surface. We studied the degradation of the hydrophobic layer in soils from two fire... more
In a wild fire, organic volatile compounds from vegetation condense on soil particles forming a hydrophobic layer several centimeters below the soil surface. We studied the degradation of the hydrophobic layer in soils from two fire sites. One site is located in a montane woodland (Wood Camp, Logan Canyon, UT) that burned in 2006. The second site is located in an arid pinyon pine/juniper stand in Milford Flats, Beaver County, UT that burned in 2007. Both sites were sampled in 2008. In situ measurements of hydrophobicity demonstrated highly hydrophobic layers a few centimeters below the surface at both sites in contrast with unburned control sites, where hydrophobicity was observed at the surface but fell off sharply with depth. Samples of surface and subsurface soil were collected from the burned and unburned areas at both sites. Subsamples of all the soils were placed in microlysimeters, treated with acid snowmelt, elevated temperatures (30°C - 47°C), and UV light. After the treatm...
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ABSTRACT In the arid and semiarid western United States, accurate measurement of soil salinity by electrolytic conductivity can be a challenge due to the formation of ion pairs in the high ionic strength soil solutions that affect... more
ABSTRACT In the arid and semiarid western United States, accurate measurement of soil salinity by electrolytic conductivity can be a challenge due to the formation of ion pairs in the high ionic strength soil solutions that affect estimates of the total quantity of ions in solution. Continued underestimation of total dissolved solids (TDS) threatens the long-term sustainable management of irrigated agricultural lands in regions faced with a threat of soil salinization. This study aims to improve estimates of soil salinity in calcareous soils. We hypothesized that saturation paste extracts can be diluted to a point where ion pair formation is minimized, so that the electrical conductivity (EC) of the saturation paste extract (ECe) can be used to more accurately predict soil salinity. Results of an analytical conceptual model using salt solutions and ion speciation modeling of these solutions suggest that 0.03 to 0.05 dS m(-1) is the optimal EC range beyond which dilutions produce negligible decreases in EC and where approximately 99% of the ion species occur as free ions. Diluting soil saturation paste extracts to conductivities <0.05 dS m(-1) (e. g., in our samples by a factor of approximately 1000), minimized ion pairing as supported by analysis of ions in solution, solution speciation with visual Minteq, and comparisons of calculated TDS (in mmol L-1). To therefore improve the estimates of salinity in calcareous soils, we recommend diluting the saturated paste extracts to EC < 0.05 dS m(-1), computing TDS from the diluted EC values, and then multiplying the TDS by the dilution factor.
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ABSTRACT Ceramic aggregates (Turface® and Profile®) are common soilless media components, but their sorption/desorption chemistry is poorly understood. We investigated: labile (readily desorb-able or readily plant-available) ion... more
ABSTRACT Ceramic aggregates (Turface® and Profile®) are common soilless media components, but their sorption/desorption chemistry is poorly understood. We investigated: labile (readily desorb-able or readily plant-available) ion concentrations; the effect of rinsing and soaking pretreatments on labile ions; sorption of applied nutrients; and nutrient uptake from the aggregates by plants. Variability in labile ions was extremely high among bags of aggregates. Manganese, boron, magnesium, calcium, sulfur and potassium were most likely to desorb in excess for plants. Phosphorus, iron, copper and zinc were sorbed by the aggregates; only copper was found nearly deficient in plant tissue. Rinsing and soaking pretreatments adjusted labile ions to more suitable concentrations for plants. However, growth data suggested a worst-case scenario of high levels of labile ions may not be mitigated by these pretreatments. With frequent leaching after planting or where the aggregates are a minor component of media, excessive nutrient uptake would likely be limited.
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Traditional microscopy methods for the detection and quantification of Cryptosporidium parvum in soil matrices are time-consuming, labor-intensive, and lack sensitivity and specificity. This research focused on developing a qPCR protocol... more
Traditional microscopy methods for the detection and quantification of Cryptosporidium parvum in soil matrices are time-consuming, labor-intensive, and lack sensitivity and specificity. This research focused on developing a qPCR protocol for the sensitive and specific detection and quantification of C. parvum in natural soil matrices and soil-water extracts. The physico-chemical parameters - lysis media, number of thermal shocks and thawing temperatures - controlling DNA extraction efficiency were investigated. Experimental results identified oocyst age as a critical parameter affecting oocyst disruption and quantification. The most efficient oocyst disruption method for C. parvum oocysts regardless of their age was established as 5 thermal shocks with thawing at 65°C in Tris-EDTA (TE) buffer. In addition to the purification columns used to remove PCR inhibitors present in environmental matrices, a combination of 3mM MgCl(2) and 600ng/μl BSA yielded the highest amplicon yield for both young and aged oocysts. Sucrose flotation was determined to be a better oocyst isolation method than two-phase flotation. The optimized parameters for DNA extraction and the qPCR assay resulted in very specific and sensitive detection of C. parvum. Minimum detection limits were 0.667 for young C. parvum oocysts and 6.67 for aged C. parvum oocysts per PCR reaction. The accuracy of the detections and quantifications was 0.999. Protocol performance was tested in contrasting soil samples and soil-water extract samples on the basis of percentage of recovery (PR) values. Depending on the number of oocysts used to inoculate the samples, the average PR values ranged from 7.2 to 43.5%, 29.3-52.5%, and 11.5-60.8% for Trenton, Greenson, and Sparta soil-water extracts, respectively, and 12.1-77% for DI water. PR values ranged from 4.3% to 107.8% for Trenton, Greenson and Sparta soil samples.
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ABSTRACT Soil salinization is of great concern in the irrigated arid and semi-arid western U.S. due to its threat to sustainable agricultural productivity and thus is closely monitored. The measurement of electrical conductivity in... more
ABSTRACT Soil salinization is of great concern in the irrigated arid and semi-arid western U.S. due to its threat to sustainable agricultural productivity and thus is closely monitored. The measurement of electrical conductivity in saturated paste extracts (ECe) is the standard to which other salinity estimation methods are referenced. Since this method is laborious, the preparation of saturated pastes subject to bias, and salinity estimates by electrical conductivity (EC) subject to chemical artifact, numerous other methods have been proposed. These include EC measurements in diluted saturated paste extracts (ECed), direct measurement of EC in soil pastes (“Bureau of Soils Cup” method, ECcup), and EC based on electromagnetic induction (ECH25ECe). The main objective of this paper is to compare these four saturated paste-related methods of estimating salinity with respect to specific soil management goals. Comparison of the methods across six soil depths and three textural groups demonstrates that estimates of salinity are significantly influenced by the method, depth of sampling, and soil texture. Whereas ECe and ECcup estimates differed significantly from each other and from those of the other methods, ECH25ECe and ECed estimates were similar. In addition, high correlations between estimates of salinity by ECH25ECe and ECe indicate their similarity and suggest the suitability of the ECH25ECe method as a reference parameter for monitoring salinity. Thus, the suitability of the ECH25ECe method is drawn from its similarity to 1) the superior ECed method, which corrects for salinity underestimation due to ion pair formation, and 2) the ECe method, which is the standard method against which other salinity estimates are traditionally compared. This finding was consistent across all depths, the three texture groups, and the combinations of method and depth or texture groups. The high coefficient of variation in ECe and ECcup highlights the subjectivity of these methods and raises questions about the choice of ECe as standard for salinity estimates. These results therefore suggest that the ECH25ECe method (which requires few collocated but representative ECe measurements) be used to rapidly and reliably monitor salinity in calcareous soils of arid and semiarid regions.
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ABSTRACT The occurence of the parasitic protozoan Cryptosporidium parvum in rural and agricultural watersheds due to agricultural activities and wildlife is inevitable. Understanding the behavior of C. parvum oocysts in the environment is... more
ABSTRACT The occurence of the parasitic protozoan Cryptosporidium parvum in rural and agricultural watersheds due to agricultural activities and wildlife is inevitable. Understanding the behavior of C. parvum oocysts in the environment is critical for the protection of public health and the environment. To better understand the mechanisms by which the pathogen moves through soils and contaminates water resources, we study their mobility under conditions representative of real-world scenarios, where both C. parvum and chemicals that affect their fate are present in soils. Surfactants occur widely in soils due to agricultural practices such as wastewater irrigation and the application of pesticides or soil wetting agents. They affect water tension and, consequently, soil infiltration processes and the air-water interfaces in soil pores where C. parvum may be retained. We investigate the effects of surfactants on the mobility of C. parvum oocysts in agricultural soils from Illinois and Utah under unsaturated flow conditions. As it is critical to examine C. parvum in natural settings, we also developed a quantification method using RT-PCR for monitoring C. parvum oocysts in environmental soil and water samples. We optimized physico-chemical parameters to disrupt C. parvum oocysts and extract their DNA, and developed isolation methods to separate C. parvum oocysts from colloids in natural soil samples. The results of this research will lead to the development of an accurate and sensitive molecular method for the monitoring of C. parvum oocysts in environmental soil and water samples, and will further our understanding of the mechanisms controlling the behavior of C. parvum oocysts in soils, in particular the role of vadose zone processes, sorption to soil and surfactants.
As the world population increases, strategies for sustainable agriculture are needed to fulfill the global need for plants for food and other commercial products. Nanoparticle formulations are likely to be part of the developing... more
As the world population increases, strategies for sustainable agriculture are needed to fulfill the global need for plants for food and other commercial products. Nanoparticle formulations are likely to be part of the developing strategies. CuO and ZnO nanoparticles (NPs) offer potential as fertilizers, as they provide bioavailable essential metals, and as pesticides, because of dose-dependent toxicity. Effects of these metal oxide NPs on rhizosphere functions are the focus of this review. These NPs at doses of ≥10 mg metal/kg change the production of key metabolites involved in plant protection in a root-associated microbe, Pseudomonas chlororaphis O6. Altered synthesis occurs in the microbe for phenazines, which function in plant resistance to pathogens, the pyoverdine-like siderophore that enhances Fe bioavailability in the rhizosphere and indole-3-acetic acid affecting plant growth. In wheat seedlings, reprogramming of root morphology involves increases in root hair proliferatio...