The National Technical Committee for Hydric Soils developed the Hydric Soil Technical Standard (HSTS) to identify a functioning wetland (hydric) soil using quantitative measurements of saturation and anaerobic conditions. We used the HSTS to assess wetland restoration success and to compare surface treatments designed to replicate microtopographic relief found in forested wetlands. Experiments were conducted on a wetland restored from agricultural fields in eastern NC where monitoring stations were installed across three surface treatments in the restored wetland: 1) a microtopography (MT) treatment created by roughing the soil surface to mimic the uneven surface of forested wetlands, 2) a crown removal treatment imposed by grading the field flat, and 3) a control treatment that had no surface alteration. Monitoring stations were also installed in a nearby nonriverine swamp forest as a reference wetland. Weekly measurements of water table depth and redox potential were collected for 15 months. Soil at all monitoring stations met the HSTS, indicating that functioning hydric soils were restored. Although a significant difference between surface treatments was not detected, the MT treatment resulted in anaerobic conditions most similar to the reference wetland, signifying that this type of surface treatment should be considered for wetland restoration of areas with smooth surfaces. The HSTS proved to be a useful tool in evaluating wetland restoration success and microtopographic effects. Microtopographic relief did not create nonhydric areas as measured by HSTS; however, microtopographic relief is likely to influence plant establishment.

Agricultural management decisions that influence biological activity and diversity include tillage, fertilizer and pest-control inputs, and crop rotations. Our research objective was to characterize relationships between biological and physical properties resulting from long-term agricultural management decisions. A nine-year old factorially-designed field experiment was used to examine the effects of tillage (moldboard plow or strip-tillage), input (synthetic fertilizers and pesticides or inputs approved for organic certification programs), and crop rotation (continuous staked tomatoes or 3-year vegetable rotation) on a suite of biological and physical soil parameters. Biological measurements included microbial, nematode, and earthworm community composition, soil respiration and N mineralization potential, enzyme activity, and microbial biomass. Physical property measurements included aggregate stability, bulk density, and pore-size distribution. Biological properties generally responded to all treatment combinations, but tillage provided the strongest treatment effect in most cases. Compared to strip-tillage, tillage consistently yielded significantly lower values for the following biological measurements: total C and N, above-ground biomass, microbial biomass, enzyme activity, soil respiration, N mineralization, some nematode trophic groups, and earthworms. Compared with organic inputs, synthetic inputs consistently induced significantly lower values for the following biological measurements: microbial biomass, enzyme activity, some nematode trophic groups, and soil respiration. An examination of relationships between biological and physical parameters using redundancy analysis revealed that microporosity was the physical property that was most strongly correlated with most biological parameters. Soil organisms responded to our treatments in the following order: tillage > input > rotation.

Residential lawn management practices (mowing, fertilizer, irrigation, reseeding, and aeration) result in aesthetically appealing landscapes, but can result in nutrient losses via overland flow or gaseous losses to the atmosphere (e.g. nitrous oxide - N2O). The overall objective of this study was to determine the effect of lawn management on nutrient losses from residential lawns. The specific objectives were: modify a passive sampling system to determine nutrient loads due to overland flow from lawns; evaluate differences in overland flow frequency, volumes, and nutrient losses during rainfall events (⥠2.54 cm); and compare N2O losses following rainfall events. Three lawn schemes were studied: a high maintenance fescue (Festuca arundinacea) lawn (HMFL), a low maintenance fescue lawn (LMFL), and a mixed forested residential landscape (RFL). The modified passive sampling system allowed 100% recovery of overland flow and demonstrated that differences in maintenance influenced the overland flow frequency, volumes, and nutrient losses. The LMFL had the greatest overland flow volumes and nutrient unit area loads, although N and P concentrations in overland flow exceeded USEPA recommendations from all three lawns. Nutrient losses (g ha-1 yr-1) from all three residential landscapes were 1000 times less than fertilizer (kg ha-1 yr-1) and throughfall (kg ha-1 yr-1) inputs, due in part to the presence of well-structured soils (low bulk densities and high infiltration rates). Irrigation practices between the HMFL and LMFL explained the differences in overland flow volumes and nutrient loads, especially during the first half of the study when drought conditions existed at the study site (Cary, North Carolina). Lack of irrigation in the LMFL resulted in early dormancy, a minimal thatch layer and lower plant density, resulting in higher volumes of overland flow. Trends in the N2O losses from the HMFL and LMFL were associated with timing of fertilizer applications, presence or absence of irrigation, and seasonal growth patterns of the fescue. For the RFL, the presence of a decomposing litter layer limited N2O production. Well-maintained residential lawns, receiving recommended fertilizer N applications and frequent irrigation, reduce nutrient losses via overland flow but may provide optimum conditions for greater N2O fluxes.

Subsurface solute transport is a major mechanism that contributes to the contaminant load in both surface and ground waters. Among these contaminants are plant nutrients that if transported in excessive amounts to surface waters can cause adverse effects on humans and animals, as well as negative impacts on aquatic life. The general objective of this study was to conduct a field evaluation of subsurface solute transport in the capillary fringe (CF) and shallow ground water (SGW) and their contribution to nutrient load in the ditches prior to restoration of a Carolina Bay. Specifically, this study was aimed at evaluating: a) the horizontal flow of bromide (Br-) in the CF and SGW under field conditions, b) the fate of nitrate (NO3-) in the CF and SGW in a sandy field site drained by ditches, and c) the possible contribution of subsurface flow to the increased nutrient load in drainage ditches at a drained Carolina Bay following storm events. The study was conducted in Juniper Bay, a drained Carolina Bay in Robeson County, NC. A solute transport experiment was conducted at a sandy site in the Bay where a solution containing Br- and NO3- was applied into an auger hole dug to about 10 cm above the CF during the time of application. The transport of Br- and NO3- in the CF and SGW was monitored by frequently collecting soil water samples using tension lysimeters installed at depths of 45, 60, 75, 90 and 105 cm at lateral distances of 20, 60, 120, 220 and 320 cm from the auger hole along the general direction of the ground water flow. A representative monitoring site from each of the Bay?s mineral and organic soil areas was also chosen for a year-long monitoring of fluctuations in nutrient concentrations in water samples from the Bay?s main ditch exit as well as from the vadose zone, ground water and lateral ditches. Soil solution from the vadose zone and ground water samples were collected using tension lysimeters installed at 15-cm depth intervals from 15 to 120, and 30 to 180 cm depths at the mineral and organic soil sites, respectively. Ground water samples were collected from three fully perforated wells. Seven piezometers installed at each site also allowed collection of ground water samples from different depth intervals below the water table The direction and magnitude of the subsurface hydraulic gradient at the monitored sites were also determined using the three-point technique. Lateral transport of Br- in the CF was observed in the direction of ground water movement up to 320 cm from the auger hole where solutes were applied. The Br- plume from the unsaturated zone that entered into the CF tended to stay and move horizontally in the CF until it was partially moved into the ground water by the fluctuating WT following rain events. The normalized concentrations (concentration in soil solution/concentration in the applied solution) of both NO3- and Br- in water samples collected from CF were comparable for all distances from the application spot. However, in the groundwater, the normalized concentration of NO3- was substantially lower than the normalized Br- concentrations. We believe the reduction in NO3- concentration in the ground water was due to denitrification. Results from the nutrient monitoring experiment reveal that the sample taken from the main ditch exit following a 5 cm d-1 storm event had higher concentrations of total organic carbon (TOC), phosphates (PO4-P), calcium (Ca) and magnesium (Mg) compared to the average of samples collected during baseflow conditions. The same was also observed for samples collected from the vadose zone especially at depths closer to the soil surface where organic carbon and extractable Ca, Mg and PO4-P contents were higher. Higher concentrations of these solutes in the ditches and vadose zone coincided with observed increase in the magnitude of the groundwater hydraulic gradient. In addition, it was observed that following the storm events, the direction of the ground water hydraulic gradient tended to become more perpendicular to the nearby lateral ditch suggesting that the route taken by the water as it moves in the subsurface towards the ditch is shortened. We believe that the increase in concentration of PO4-P, Ca, Mg and TOC in the soil solution at certain depths in the soil profile coupled with their higher rate of movement in the subsurface towards the ditch following the storm event should have contributed to the increase in concentration of such nutrients in the ditches.

Knowledge of the effect of reduced soil redox conditions on P dissolution is needed to better assess P mobility to surface or ground water. The objectives of our study were to determine the effect of microbial reduction on P dissolution and determine mechanisms of P release in a reduced soil. Duplicate suspensions of silt+clay from a Cape Fear sandy clay loam were reduced in a continuously-stirred redox reactor for 40 d. We studied the effects of three treatments on P dissolution: (i) 2 g dextrose kg-1 solids added as a microbial carbon source at time 0 d; (ii) 2 g dextrose kg-1 solids split into three additions at 0, 12, and 26 d; and (iii) no added dextrose. Regardless of treatment or variation in the intensity of reduction rates, dissolved reactive P (DRP) increased up to 7-fold from 1.5 to 10 mg L-1 and was linearly related (R2 = 0.79) with dissolved organic C. Dissolved Fe and Al and pH also increased, suggesting the formation of aqueous Fe- and Al-dissolved organic matter (DOM) complexes. Separate batch experiments were performed to study the effects of increasing pH and citrate additions on PO4 dissolution under aerobic conditions. Increasing additions of citrate increased concentrations of DRP, Fe, and Al, while increasing pH had no effect. Results indicated that increased DOM during soil reduction contributed to the increase in DRP, perhaps by competitive adsorption or by formation of aqueous ternary PO4-Fe-DOM or PO4-Al-DOM complexes.

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>