<p> Concerns over delayed soil warming and drying have hindered adoption of conservation tillage practices in frigid environments. Our objectives were to evaluate the effects of chisel plow (CP), vertical tillage (VT), strip tillage with coulters (STC), and strip tillage with shanks (STS) on soil warming and drying and their potential consequences to crop yields. A two-year study was conduct at three full-scale, producer-managed, corn-soybean fields in the Red River Valley of eastern North Dakota and western Minnesota. Tillage treatments were assessed to measure crop residue cover, soil temperatures, soil volumetric water contents, crop yields, and other metrics. Our study indicated significant differences for many soil physical and chemical parameters, but little to none for soil warming and crop yields. Yield differences were attributed to varying fertilizer management practices, timing, and application method. These findings emphasize the importance of field management practices that compliment conservation tillage for obtaining competitive crop yields. </p><p>

<p> One of the least researched phenomena within the alpine regions of mountain biomes is the combination of primitive plants, algae, fungi, and lichens that are generally referred to as biological soil crusts. Sites containing well-developed biological soil crusts were examined in a variety of alpine, non-forested, vegetated landscapes in the North Cascade Mountains of Washington, USA. For each site, data were recorded for percent ground cover of biological soil crusts, slope aspect, and slope gradient of the terrain where the crust communities were located. For all of the sites, biological soil crusts were common, with a percent ground cover median of 29% and a range of 11% to 73%. The arrangement of the biological soil crusts on all sites was quite similar: all were clumped, as opposed to single, and random, as opposed to uniform. All of the soil crusts were found on soil exposed to direct sunlight. Few, if any, crusts were found in the shade of heavy forbs, or forest, or under accumulations of organic litter. When biological soil crusts were found associated with higher-order vegetation, it was with sparse graminoids, ericaceous woody shrubs, and stunted or krummholz Pinaceae trees. The biological soil crusts from this study exist on all locally undisturbed soil slope-gradients from 0% to almost 100%, and occurred on all aspects except for those in the Southwest quadrant. This study contains an extended literature review for desert and high latitude circumpolar crusts, as well as alpine biological soil crusts. Studies of biological soil crusts in subalpine and alpine environments are not common; it is hoped that this study will stimulate more research interest in these often overlooked pioneer biotic communities.</p>

<p> Soil studies have traditionally been limited to the upper 2-m, while deep regolith &ndash; semi-consolidated materials from soil to bedrock &ndash; remains relatively unexplored, leaving many questions about the weathering processes of the near earth surface. Regolith (soil plus weathered bedrock) was studied across an elevation transect (405 m to 2700 m) of the west slope of southern Sierra Nevada mountains as a bioclimosequence. </p><p> In chapter one, effects of subtle differences in lithology and temperature were evaluated to measure degree of pedogenesis in regolith at rain- and snow- dominated sites. Biotite content in fine sand fractions was positively correlated with regolith thickness at rain-dominated and snow-dominated sites. Mineral grain size was negatively correlated with regolith thickness at the rain-dominated site. Meanwhile, the degree of regolith transformation, evaluated based on clay and secondary Fe oxide concentrations, was related to annual heat energy load from 0.5 to 10-m hard bedrock, where the proxy of energy input was mediated by temperature with depth. </p><p> In chapter two, a significant reservoir of carbon (C) within weathered bedrock was discovered. Small measurable amounts of C detected in deep regolith summed to large pools at locations where the regolith was thick. Although temperature and precipitation not effected on C density in deep regolith, the influence of climate had an indirect effect on C stock because it governed weathered bedrock thickness. Weathered bedrock had been reported to store deep C by 9% to 30% of the total regolith C inventory due to thickness of 0.7 to 7.6 m. Furthermore, a hypothetical scenario of global C stocks in weathered bedrock of 4-m thickness is 201 Pg, which help to explain a &ldquo;hidden&rdquo; C sink in the global C budget. In the third chapter, physical, chemical and mineralogical properties were measured at three elevations to understand climatic controls on weathering in soil and weathered bedrock. Evidence of chemical weathering was most pronounced in soil at the mid-elevation, while evidence of physical weathering was greatest in weathered bedrock at the high elevation where deep water percolation was highest. The concentration of nutrients was lower in weathered bedrock than that of soil, but due its thickness weathered bedrock was reservoir of plant essential nutrients. Moreover, available water content was large when summed over weathered bedrock thickness.</p><p> New spatial trends in ecosystem services were revealed by expanding our concept of soil to include deep regolith. This work was first to document factors that influence spatial trends of regolith (soil to weathered bedrock) characteristics in the Sierra Nevada. Characterization of deep regolith under different weathering environments improves our understanding of regulating factors for ecosystems health. The differentiation between weathering trends of soil and weathered bedrock could be used in the future to predict conditions in weathered bedrock at large scales.</p><p>

Time of planting plays a critical role in nitrogen (N) uptake by rye cover crop (CC). Even a few days of delay in planting can severely decrease CC performance. Evaluating the amount of N accumulation related to time of planting is critical to the farmer who has to optimize the winter rye planting date based on completion of corn harvest, suitable weather conditions and time availability for fall manure application. Winter rye cover crop was planted at 6 planting dates in fall from mid August to early October at weekly intervals from 2004 to 2009. The results suggest that delay from critical planting date (CPD) will decrease rye N uptake dramatically. Suggested CPDs for northwest parts of Massachusetts are not applicable because they are too early (third to fourth week of August). CPDs for central parts of the State are from first to second week of September. Farmers in these zones can take advantage of cover crop by a better time management and planting no later than CPD. In Eastern areas of Massachusetts CPD is the third week of September. By evaluating the effect of planting date on rye growth and N accumulation throughout the State, this model provides a powerful decision making tool for increasing N recovery and reducing nutrient leaching. Sixteen units of cost effective and accurate automated lysimeters were designed and installed to measure post-harvest nitrate leaching from a rye cover crop field during the falls and winters of 2007 to 2009. The electronic system was designed to monitor soil tension and apply the equal amount of suction to the sampling media. Hourly data from soil tension and vacuum applied to the system were collected and stored by each unit. A safety system was designed for protecting vacuum pump against unexpected major vacuum leakage events. The controller can be easily reprogrammed for different performance strategies. Other major parts of lysimeter included the power supply systems, vacuum pump, vacuum tanks, sampling jars, suction cups and plates, and electronic valves. The electronic system showed a very reliable and accurate performance in the field condition.

Isoxaflutole is a new pre-emergence herbicide which undergoes rapid conversion to a diketonitrile metabolite (DKN) in soil. In soil the half-life of isoxaflutole is very short, but the half-life of DKN is much longer. Sorption studies were conducted with five soils varying in physical and chemical properties using the batch equilibration technique. Analysis of 14C-ring labeled isoxaflutole and DKN was performed using liquid scintillation counting, and sorption data were fitted to the Freundlich model. Isotherms of isoxaflutole and DKN in all the soils were nonlinear as depicted by the exponent ( n < 1.0), indicating differential distribution of sorption site energies in various soils. Isoxaflutole and DKN sorption increased with an increase in organic matter content of soils and decreased as the soil pH increased from 4.5 to 8.5, which was depicted by the reduction of KF values. Clay content of the soils did not have a high correlation with KF values, while the sorption of isoxaflutole was not influenced by the Ca2+ concentration in the soil solution. There was an increase in the sorption of DKN with an increase in Ca 2+ concentration of the soil solution, while the net sorption constant (Kd) was correlated to the organic matter content of the soils. A high correlation existed between the desorption coefficient, KFd and the organic matter content of soils, while the clay content did not greatly influence the desorption of DKN. Although the sorption of DKN was generally reversible, a sorption-desorption hysteresis was apparent in all soils. The site energy distribution curves emphasized the fact that DKN binds tightly to soils with higher organic matter content, and a larger proportion of DKN was retained by those soils. In soils with high organic matter content, the sorption-desorption hysteresis was mainly governed by organic matter content, but in soils with low organic matter, clay content played an important role. When isoxaflutole and DKN were added to soil, the carbonyl stretching frequency decreased as observed in the diffuse reflectance Fourier transformed infrared (DRIFT) spectra. In conclusion, the potential for leaching through soil and crop injury due to isoxaflutole and its metabolite would decrease as soil organic matter and clay content increase.

Humic substances (HS) are major components of soil organic matter (SOM). Advances on characterization of HS and their interaction with minerals can provide a more fundamental understanding of HS functions in soils. The objectives of this research were to investigate potential fractionation of humic acid (HA) upon adsorption on minerals and to determine any variation on structure and sorption properties of humin extracted by different methods. Nuclear magnetic resonance (NMR) spectra, for the first time, provided direct evidence that HA was fractionated during adsorption on mineral surfaces. Aliphatic fractions of HA were preferentially adsorbed while aromatic fractions were more likely to be left in solution. The bound HA fractions had higher sorption linearity (N) and affinity (KOC) for phenanthrene than the source HA. For montmorillonite and kaolinite, the KOC values of adsorbed HA were up to several times higher than that of the source HA as a result of fractionation. Extraction procedures had substantial influences in structure and sorption characteristics of humin. Humin from 0.1 M NaOH exhaustive extraction and 6 M HF/HCl extraction at 60°C had relatively more aliphatic components as compared with 1 M HF extracted humin. The treatment of 6 M HF/HCl at 60°C reduced more than 50% carbohydrate components (50-108 ppm) and enriched amorphous poly(methylene) domains. The NaOH exhaustively extracted humin had the most nonlinear sorption isotherms and the HF extracted humin had the lowest KOC. We concluded that both NaOH and NaOH-HF procedures were appropriate approaches for humin extraction but the extraction with 6 M HF/HCl at 60 °C would be discouraged for use due to structural modifications of humin both chemically and physically. Segmental mobility of HA in solution was also explored by NMR relaxation. Proton spin-lattice relaxation time (T1) of HAs ranged from 0.3 to 0.8 s in d6-DMSO, and from 0.26 to 2.3 s in 0.5 M NaOD at 300 MHz. Proton correlation time of HA in solvents was in an order of 10-10 s. Carbohydrate was identified as the largest and the most immobile components while aliphatic and aromatic fragments were relatively smaller and more mobile in aqueous solution.

Humic substances (HS) are the major components of soil organic matter (SOM), which are by far the most abundant organic materials in the environment. Advances on structural characterization of HS and their interaction with clay minerals will provide a more fundamental understanding of HS functions in such important roles as sorption of anthropogenic organic contaminants, stabilization of soil aggregates, and C sequestration. The objectives of this research were to determine any variation in structure and sorption properties of humic acids (HAs) and humins sequentially extracted from a soil and investigate characterization and fractionation of HA and relatively small carboxylic acids upon adsorption on clay minerals. In a phenanthrene sorption study of sequentially extracted HAs and humins, there were significant chemical and structural differences among the HA fractions and humins, and sorption was greatly affected by chemical structure and composition of humic substances, even from the same soil. A positive trend was observed between the sorption coefficient and the aliphaticity. Humin fractions with the highest aliphatic C contents and the lowest polarity showed the highest sorption capacity and nonlinearity as compared with the HAs. A negative relation was shown between the sorption capacity and polarity of HAs. The aliphatic-rich SOM in this study had less polar moieties, but had relatively high Koc. Therefore, the polarity of SOM is likely one of the important parameters controlling sorption of hydrophobic organic chemicals (HOCs). Adsorption of SOM onto clay minerals modifies their surfaces and reactivity and strongly influences the fate of organic contaminants and other species in soils and sediments. For investigation of the structural and conformation changes of HA and clay-HA complexes after sequential adsorption by goethite, kaolinite, and montmorillonite, UV-Visible spectroscopy, high performance size exclusion chromatography (HPSEC), Fourier transform infrared (FT-IR) spectroscopy, and solid-state 13C nuclear magnetic resonance (NMR) spectroscopy were employed. Aliphatic rich HA fractions with polar functional moieties readily adsorb to the goethite surface, while aromatic fractions were left in solution. Similar to HA fractionation onto goethite, paraffinic fractions and polar aliphatic fractions sorbed preferentially on montmorillonite, but aromatic functional moieties likely remained in solution. However, paraffinic fractions were observed on kaolinite surfaces although the adsorbed proportion of these fractions was low. Because of high broken edge areas, kaolinite has more adsorption sites for carboxylic and carbonyl rich fractions than montmorillonite. With respect to MW fractionation after sorption, relatively low molecular weight (MW) HA fractions had a greater affinity for the goethite surface from the analysis and inference of the HPSEC chromatograms, which differs from the reported results in the literature. The low MW HA fractions might be intercalated into the interlayer of montmorillonite and high MW HA fractions adsorbed on external surfaces, which results in the adsorption of relatively wide range of MW HA fractions. The binding mode of small HA fractions on the clay minerals may be ligand exchange and/or electrostatic interaction, which gives HA-clay complexes new hydrophobic sorption sites for high MW HA fractions. To obtain information on the nature of the interactions between SOM and clay mineral surfaces, the adsorption of dicarboxylic acids by kaolinite and montmorillonite at different pH conditions was investigated using in situ attenuated total reflectance Fourier transformed infrared (ATR-FTIR) and ex situ diffuse reflectance infrared Fourier transformed (DRIFT) spectroscopy. The sorption was highly pH dependent and related to the surface characteristics of minerals; adsorption of dicarboxylic acids (succinic acid, glutaric acid, adipic acid, and azelaic acid) was the highest at pH 4 as compared with those at pH 7 and 9, and the sorption capacity of montmorillonite was greater than that of kaolinite. Furthermore, the complexation types, inner- or outer-sphere, depended upon dicarboxylic acid species, pH, mineral surfaces, and solvent conditions. Most samples tend to have outer-sphere adsorption with the mineral surfaces at all tested pHs. However, inner-sphere coordination between the carboxyl groups and mineral surfaces at pH 4 was dominant with freeze-dried complex samples. Therefore, organic acids in an aqueous environment prefer to adsorb onto kaolinite and montmorillonite by outer-sphere complexation, but inner-sphere complexation is favored under dry conditions. These results imply that organic acid binding onto clay minerals under dry conditions is stronger than that under wet conditions. The stable NOM/mineral complexes formed by frequent wetting-drying cycles in nature may resist chemical/microbial degradation of the NOM, which will affect carbon storage in the environment and influence the sorption of organic contaminants.

<p>The majority of the current production, use, and disposal of engineered nanomaterials (ENMs) occur in terrestrial environments, and consequently terrestrial ecosystems are and will increasingly be some of the largest receptors of ENMs at all stages of their life cycles. In particular, soil is predicted to be one of the major receptors of ENMs due to ENM-contaminated biosolid fertilizer and nanopesticide application to agricultural fields, runoff from landfills or ENM-bearing paints, or atmospheric deposition. Both agricultural and natural systems are at risk to ENM contamination via these release scenarios, which makes it necessary to understand the interactions between ENMs, soils, and soil organisms such as plants in order to predict their impacts in real-world scenarios. Gravity-driven vertical transport of TiO2, CeO2, and Cu(OH)2 engineered nanomaterials (ENMs) and their effects on soil pH and nutrient release were measured in three unsaturated soils. ENM transport was found to be highly limited in natural soils collected from farmland and grasslands, with the majority of particles being retained in the upper 0-3 cm of the soil profile, while greater transport depth was seen in a commercial potting soil. Physical straining appeared to be the primary mechanism of retention in natural soils as ENMs immediately formed micron-scale aggregates, which was exacerbated by coating particles with Suwannee River natural organic matter (NOM). Changes in soil pH were observed in natural soils contaminated with ENMs that were largely independent of ENM type and concentration. These changes may have been due to enhanced release of naturally present pH-altering ions (Mg2+, H+) in the soil, likely via substitution processes. This suggests ENMs will likely be highly retained near source zones in soil and may impact local communities sensitive to changes in pH or nutrient availability. Few studies have investigated the influence of environmental conditions on ENM uptake and toxicity, particularly throughout the entire plant life cycle. Here, soil-grown plants (Clarkia unguiculata, Raphanus sativus, and Triticum aestivum) were exposed until maturity to TiO2, CeO2, or Cu(OH)2 ENMs under different illumination intensities, in different soils, and with different nutrient levels. Fluorescence and gas exchange measurements were recorded throughout growth and tissue samples from mature plants were analyzed for metal content. ENM uptake was observed in all plant species, but was seen to vary significantly with ENM type, light intensity, nutrient levels, and soil type. Light intensity in particular was found to be important in controlling uptake, likely as a result of plants increasing or decreasing transpiration in response to light. Significant impacts on plant transpiration, photosynthetic rate, CO2 assimilation efficiency, water use efficiency, and other parameters related to physiological fitness were seen. The impacts were highly dependent on environmental conditions as well as ENM and soil type. Notably, many of these effects were found to be mitigated in soils with limited ENM mobility due to decreased uptake. These results show that abiotic conditions play an important role in mediating the uptake and physiological impacts of ENMs in terrestrial plants.

Phytoremediation is a tool that uses plants that can absorb and accumulate metals in harvestable portions of the plant to cleanse contaminated soils. Most metals are more soluble in soils with an acidic pH. Nitrogen fertilizers acidify pH by different reactions in the soil. Goals of this research were: (1) develop a zinc-contaminated soil; (2) determine effects of nitrogen fertilizers on soil-zinc availability; (3) determine Zn-phytoextraction potential of Brassica juncea Czern. and Festuca arundinacea Schreb.; and (4) determine concentrations of nitrogen fertilizers needed to maximize Zn solubility in soils. After a 14-day incubation period, very little Zn in the soil was water-extractable, which suggested that Zn was reacting with the soil; therefore, an incubation time of 14 days was utilized. Morgan's solution, extracted higher concentrations of Zn than water. If soils were sequentially extracted with water, Morgan's solution, and Mechlich-3 solution, water extracted the least amount of Zn, Morgan's solution extracted higher concentrations than water or Mehlich 3, but Mehlich 3 extracted higher concentrations than water. Lowest pH values occurred with additions of urea (pH 5.18), sludge (pH 4.89), or calcium nitrate (5.26) than with compost (pH 5.33), manure (pH 5.50), or no fertilizer (pH 5.40) or if N was supplied at 400 mg/kg (pH 4.91). Brassica did not germinate well or survive in soil-Zn concentrations greater than 125 mg/kg. Soil-Zn concentrations utilized with brassica were 0 to 100 mg/kg. Highest accumulation of Zn was 0.29% of the dry mass, which occurred at 100 mg Zn/kg or in soils with urea added. Water-extractable Zn at this level averaged 1.1 mg/kg and Morgan's extractable Zn averaged 18 mg/kg. Fescue germinated well in soil-Zn concentrations ranging from 0 to 2000 mg/kg. The soil-Zn concentrations utilized with fescue were 0 to 1000 mg/kg. Highest accumulation of Zn by fescue was 0.33%, which occurred at 1000 mg Zn/kg or in soils with urea or sludge added. Water-extractable concentrations of Zn at this level averaged 11 mg/kg and Morgan's extractable Zn concentrations averaged 290 mg/kg. This research showed that fescue has phytoremediation potential that is as good or better than that of brassica.