Growing concerns about elevated levels of atmospheric CO2 and associated climate change have increased interest in soil C. While general increases in the adoption of conservation management practices may result in C sequestration, efficient utilization of soil as a C sink will require identification of soils with high potential for sequestration and improved methods of monitoring soil C. The objectives of this research were to: 1) evaluate the historical roots, experimental validation and subsequent impact of the C saturation relationships proposed by Jan Hassink, 2) evaluate the effects of management and texture on aggregation and C fractions using soil from two long term experiments, 3) develop new methods of structural disruption and physical fractionation that address shortcomings in existing methods, 4) evaluate the impact of antecedent C on C and aggregate dynamics and 5) evaluate the simplified MnoxC method proposed by Weil et al. (2003). Collectively, the literature we reviewed did not support broad application of simple C saturation relationships such as those proposed by Hassink but did support selective use of fine mineral content as an indicator of C storage capacity. Results from two incubation experiments demonstrated the modulating effect of antecedent C on soil C and aggregate dynamics following structural disruption and residue addition. Positive effects of residue and structural disruption on aggregation were greatest in soil with low antecedent C. Residue decomposed more rapidly in soil with high antecedent C but had a greater priming effect in soil with low antecedent C. Addition of a 15N labeled nitrate source revealed that immobilization of nitrate-N within microaggregates is a minor process irrespective of structural disruption and antecedent C. Carbon contained in microaggregates within stable macroaggregates from an organic transition experiment was sensitive to C input regime but unrelated to fine mineral content. Strong tillage system effects on C fractions, aggregation and texture (tillage intensity↑ = ↓C, aggregate stability and sand content) were identified in soil from a long term tillage system study. Permanganate oxidizable C (Weil method) was found to be a sensitive indicator of management effects on soil C particularly after correction for non-linearity.

Excessive agricultural phosphorus (P) has been a major contributor to non-point source pollution. North Carolina developed the Phosphorus Loss Assessment Tool (PLAT) to evaluate the potential P loss from agricultural fields to waterbodies via four components. Our overall goal was to evaluate the potential of using spatial data to estimate P loss without physically visiting fields since many PLAT required parameters occur in spatial formats. The objective of the first study was to assess the possibility of spatial implementation of PLAT and to compare the effect of scale on the PLAT numerical results and the associated categorical rankings. Since an important input parameter, the average annual soil loss determined by the Revised Universal Soil Loss Equation, is not directly available from field measurement, our objective in the second study was to assess the potential of obtaining RUSLE estimates, specifically the topography factor LS, through Digital Elevation Model data in a Geographic Information System environment. In the first study, two methods of whole field average (WFA) and grid average (GA) were used to compare the difference in modeling P loss at different scales. The same list of PLAT required parameters were prepared from soil test reports and spatial database at the coarse scale of whole agriculture field and the fine scale of 0.4-ha grid. Soil tolerance value was used to temporarily replace the soil loss data. In the second study, a widely used Arc Macro Language (AML) program for estimating RUSLE topographic factor LS was evaluated through two approaches of whole field (WF) and representative profile (RP) analysis on a North Carolina landscape. Watershed delineation technique was adopted to select the representative profiles based on the references of slope distributions and field subdivisions from NRCS water quality specialists. Results from the first study indicated that soluble and particulate P loss, which occupied 59.3% and 26.3% of the total P loss through WFA method, and 56.1% and 39.0% through GA method, were the major pathways. Leaching P loss from PLAT was negligible. Particulate P loss was sensitive to scale as verified by the 12.7% increase of proportion in total P loss. The difference of particulate P loss through two methods was significant (p < 0.05), but no difference of soluble P loss and P source effect was found on a 95% confidence level. The overall P loss potential through two methods exhibited no significant difference due to the neutralization effect of individual pathways. Results from the second study showed that the AML program alone was not suitable for calculating RUSLE topographic factor on a North Carolina landscape because of the significant underestimation (~35% and ~20% through WF and RP approach, respectively). The concept of representative profile indeed improved the estimation accuracy (~15%), however, the linearity of the fitted line between field measured LS and GIS-aided LS estimate was not satisfactory. An adjustment factor was proposed rectifying the RUSLE-based AML program in order to approximate field measurements. This study demonstrated the potential of implementing PLAT model and the soil loss equation using spatial parameters derived from database instead of visiting the fields. The scale of modeling in estimating particulate P loss and RUSLE topographic factor LS was important and the adjustment factor was necessary to adapt the AML program application. The accuracy of model performance needed to be improved before claiming that GIS-aided PLAT modeling will provide a complete replacement for the field measurement.

<p>Alcacio, Tim. The Molecular Scale Nature of Copper(II) and Arsenate Bonding With Goethite-Humate Complexes. In soils, interactions between clay minerals and natural organic matter are known to affect the cycling of heavy metals and anions. Contaminant structures at mineral surfaces that contain adsorbed organic matter will have a significant influence on the bioavailability of the contaminant. The structure of copper(II) and arsenate complexes on goethite in the presence and absence of adsorbed humic acid were studied with extended x-ray absorption fine structure (EXAFS) spectroscopy and with x-ray absorption near edge structure (XANES) spectroscopy. The copper(II) and arsenate formed edge shared inner-sphere surface complexes with goethite. The copper(II) itself was present in a distorted octahedral configuration, and ternary complexes involving bonding with both the humic acid and the goethite (Type A complexes) or adsorbed humic acid (Type B complexes), occurred at pH 5.6. At pH 8, the copper(II) was found to display a stronger affinity for the goethite surface and the formation of ternary complexes did not occur. The EXAFS analyses demonstrated that arsenate was present in a tetrahedral configuration and was predominantly bonded to goethite surface sites. Regardless of the level of adsorbed humic acid, the arsenic coordination environment was similar and indicated that ternary complexes could not be distinguished. <P>

<p>The purpose of this research was to measure P losses in runoff from agricultural land in the Piedmont region of the southeastern U.S. with varying soil P levels and receiving broiler litter and inorganic P fertilizers. The experimental results will be helpful for the development of the P Loss Assessment Tool in North Carolina and other P Index approaches in states with similar soil characteristics and crop management practices. A net influx of P into many areas due to high animal populations has resulted in increased potential P losses to sensitive surface waters. A typical North Carolina broiler farm and dairy farm were found to have annual P surpluses of 65 kg P/ha and 20 kg P/ha respectively. The use of low phytic acid corn varieties and phytase enzyme has the potential to reduce the P surplus on broiler farms by 25 to 58%. Phosphorus losses in runoff from Piedmont conventional till (CT) and no-till (NT) soils with varying soil P concentrations and from soils currently receiving broiler litter and fertilizer P applications were assessed. In these studies, rainfall simulation at rates of 6 and 7.6 cm/hr were utilized to collect runoff samples from crop land with a range of initial P concentrations and from plots with varying fertilizer P and broiler litter application rates, both incorporated and broadcast. Runoff samples were collected at 5-min intervals for 30 min and analyzed for reactive P (RP), algal-available (AAP), and total P (TP). Concentration of RP in runoff from CT and NT plots was positively correlated with Mehlich-3 extractable P (r2 = 0.61 and 0.7 respectively) and oxalate extractable degree of P saturation (DPS) (r2 = 0.6 and 0.61 respectively). However, only TP mass loss (kg TP/ha) in runoff from CT was correlated with DPS (r2 = 0.57). A Mehlich 3 extractable P concentration of 350 mg P/kg and a DPS of 84% corresponded to 1 mg RP/L in runoff. Incorporation of broiler litter and inorganic P fertilizer into the soil at all P application rates virtually eliminated P runoff loses and had similar P losses in runoff as the unfertilized control. Surface application of broiler litter resulted in runoff containing between 2.9 and 24.5 mg RP/L for application rates of 8 to 82 kg P/ha respectively. Mass loss of TP in runoff from surface-applied broiler litter ranged from 1.3 to 8.5 kg P/ha over the same application rates. There was no significant relationship between surface applied inorganic P application rate and RP concentrations or TP mass losses in runoff. However, there was a trend for increased RP concentrations and TP mass losses in runoff with increasing application rate. Concentration of RP and mass loss of TP in runoff from surface applied inorganic P averaged 4.9 mg RP/L and 1.1 kg P/ha over all application rates. There was no significant difference between P losses in runoff from plots receiving surface applied conventional broiler litter and broiler litter derived from birds fed a low phytic acid corn (High Available P corn). <P>

<p>Increased numbers of swine producers in North Carolina will be removing sludge from their lagoons in the next few years, mainly due to an increase in lagoons exceeding sludge capacity. Information on availability of nitrogen (N) in the sludge is needed to make improved recommendations about its use as a nutrient source for crops. The objectives of this study were to investigate possible affects related to lagoon sludges from different companies and operation types and to evaluate effects of seasonal temperatures and various application dates on the availability of N in lagoon sludge. Two separate incubation studies and one greenhouse study were conducted to quantify the N availability of the sludge. Sludges were mixed with a Wagram soil (loamy, siliceous, thermic Arenic Kandiudult) and incubated for one year at fluctuating seasonal temperatures based on four application dates (Feb. 26, June 4, Sept. 3, and Dec. 3). A second incubation experiment was conducted using sludges from three different company and operation-types. Samples were analyzed monthly for nitrate and ammonium. These sludges were also applied as the primary N source for bermuda grass, which was grown in the greenhouse, harvested and analyzed for total N. Operation effects were not detected in the incubation and greenhouse experiments. Company effects were detected in the incubation experiments yet considered to be negligible because differences were only significant (p < 0.05) at weeks 0, 2, 3, and 8. A quadratic plateau curve fit to N mineralization data for all sludge sources (r^2 = 0.52) demonstrated that most of the active organic N was mineralized after 8 weeks of incubation. Nitrogen availability for all sludges averaged 45 percent after 8 weeks for the incubation study, but only 20 percent for the 14-week greenhouse study. This may have been related to inconsistent moisture throughout the soil in pots. In the incubators with fluctuating temperatures, NH4 remained in the soil for 4 months in the simulated winter application and for only 1 month for the simulated fall and summer applications, illustrating a direct influence of temperature changes on nitrification. Sludge N availability was fit to a nonlinear regression model for a first order reaction as follows: Nt = No (1 - e^(-kt)) + Nos where: Nt = total inorganic N concentration, over time (mg N/kg); No = potentially available organic N (mg N/kg); k = first order rate constant (month^-1); t = time (month); and Nos = inorganic N concentration when time = 0. Rate constants (k) increased between simulated applications as follows: fall (0.07) < winter (0.075) < spring (0.22) < summer (0.36). Sludge applied during simulated winter temperatures released N at a relatively constant rate, as compared to simulated summer temperatures, which increased rapidly during the first 6 months, then stabilized to allow minimal increase of mineralized N for the remainder of the incubation.Predicted N availability for all temperature treatments after one year of incubation averaged 74 percent of the total N applied, supporting agronomic recommendations of 60 percent first-year plant-available N for incorporated swine lagoon sludge (NCCES, 1997). Year-long coefficients are unable to provide N availability information for short time length for growing seasons. To account for this, N availability for each month after sludge application was estimated using the first order equations for each simulated application date. <P>

<p>The solubility of heavy metal (trace metal) contaminants in soils depends on metal concentration, chemical speciation, and conditions such as pH, redox potential, and ionic strength of the soil solution. The objective of this study was to determine the dissolution (potential mobilization) of metal contaminants in response to induced changes in pH and redox potential in soils surrounding abandoned incinerators at two outlying US Marine Corps air fields: MCALF-Bogue and MCOLF-Atlantic. Concentrations of heavy metals measured in 17 soil samples ranged from 1 to 101 mg Zn/kg, 2 to 45 mg Cu/kg,3 to 105 mg Pb/kg, 0.3 to 12 mg Cr/kg, <0.01 to 0.6 mg Cd/kg, <0.1 to 0.6 mg Se/kg, 0. 5 to 81 mg Ba/kg, and 5. Decreasing redox potential (Eh) if soil samples from at the MCALF-Bogue site to 250 mV caused minimal dissolution of Cu, Zn, Pb, and Cr. <P>

Thesis (M.S.)--Montana State University--Bozeman, 2006. / Typescript. Chairperson, Graduate Committee: Robert Mokwa. Includes bibliographical references (leaves 126-128).

Thesis (M.S.)--Oregon State University, 1978. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

<p>Soil compaction is an inevitable result of agricultural practices. It alters physical properties of soil and tends to be undesirable as it adversely affects water and nutrient penetration. Furthermore, additional energy is spent to till the soil. Although a tremendous amount of research has been conducted in the area of soil compaction, the focus has been primarily on surface soil displacement.</p> <p>Realizing that the observed soil displacement is the cumulative effect from the compaction of subsurface layers, this research discusses the displacement and distributed pressure through the soil from a surface load. A given volume of soil of known density and moisture content was loaded at the surface with a slowly applied force using an Instron® testing machine. The distribution of the pressure and displacement profile from the surface to depth was measured to provide insight into the formation of the subsurface soil structures. The nonlinear exponential decay of the soil displacement (compaction) from the surface to a given depth converges to zero at the location of a hard, compact layer or a point where no soil movement occurs, regardless of the initial soil compaction. By increasing soil moisture content and decreasing soil bulk density, the vertical soil displacement increased at the surface and within the soil profile, and the pressure distribution decreased with depth. Changing the shape of loading surface had minimal effect on soil displacement.</p>

<p>Soil compaction is an inevitable result of agricultural practices. It alters physical properties of soil and tends to be undesirable as it adversely affects water and nutrient penetration. Furthermore, additional energy is spent to till the soil. Although a tremendous amount of research has been conducted in the area of soil compaction, the focus has been primarily on surface soil displacement.</p> <p>Realizing that the observed soil displacement is the cumulative effect from the compaction of subsurface layers, this research discusses the displacement and distributed pressure through the soil from a surface load. A given volume of soil of known density and moisture content was loaded at the surface with a slowly applied force using an Instron® testing machine. The distribution of the pressure and displacement profile from the surface to depth was measured to provide insight into the formation of the subsurface soil structures. The nonlinear exponential decay of the soil displacement (compaction) from the surface to a given depth converges to zero at the location of a hard, compact layer or a point where no soil movement occurs, regardless of the initial soil compaction. By increasing soil moisture content and decreasing soil bulk density, the vertical soil displacement increased at the surface and within the soil profile, and the pressure distribution decreased with depth. Changing the shape of loading surface had minimal effect on soil displacement.</p>