The long-term mobility of trace metals has been cited as a potential hazard by critics of EPA 503... more The long-term mobility of trace metals has been cited as a potential hazard by critics of EPA 503 rule governing the land application of biosolids. The objectives of this study were to assess the accumulation of Cu, Ni, Cd, and Zn within the soil profile; the distribution of exchangeable, specifically adsorbed, organic, and oxide fractions of each metal; and mass balance of Cu, Ni, and Zn 17 yr after a single biosolids application. Biosolids were applied to 1.5- x 2.3-m confined plots of a Davidson clay loam (fine, kaolinitic, thermic Rhodic Kandiudult) in 1984 at 0, 42, 84, 126, 168, and 210 Mg ha(-1). The highest biosolids application supplied 4.5, 750, 43, and 600 kg ha(-1) of Cd, Cu, Ni, and Zn, respectively. Soils were sampled to a depth of 0.9 m and sectioned into 5-cm increments after separating the Ap horizon. Total (EPA-3050B), bioavailable (Mehlich-I), sequential extraction, and dispersible clay analyses were performed on samples from the control, 126 Mg ha(-1), and 210 Mg ha(-1) treatments. Trace metals are still concentrated in the top 0.2 m with slight enrichment down to 0.3 m. More than 85% of applied Cu, Ni, and Zn are still found in the topsoil where biosolids was incorporated and 95% or more of the applied metals were accounted for with mass balance calculations. Mehlich-I results showed a slight increase in metal concentration down to 0.35 m. Biosolids application increased the concentrations of trace metals in all the extracted fractions. The major portions of Cu, Zn, and Ni are associated with the metal-oxides fraction. Dispersible clay content and water-soluble metal contents were low and except for water-soluble Zn they were not affected by biosolids application. Results from this study showed that 17 yr after biosolids application there was negligible movement of trace metals through the soil profile and consequently there is little risk of contamination of ground water at this site.
The selection of plant species is critical for the successful establishment and long-term mainten... more The selection of plant species is critical for the successful establishment and long-term maintenance of vegetation on reclaimed surface mined soils. A study was conducted to assess the capability of 16 forage grass and legume species in monocultures and mixes to establish and thrive on a reclaimed Appalachian surface mine amended with biosolids. The 0.15-ha coarse-textured, rocky, non-acid forming mined site was prepared for planting by grading to a 2% slope and amending sandstone overburden materials with a mixture of composted and dewatered, anaerobically digested biosolids at a rate of 368 Mg ha(-1) (dry weight). Tall fescue (Festuca arundinacea Schreb.), orchardgrass (Dactylis glomerata L.), switchgrass (Panicum virgatum L.), caucasian bluestem (Bothriochloa caucasia L.), reed canarygrass (Phalaris arundinacea L.), ladino clover (Trifolium repens L.), birdsfoot trefoil (Lotus corniculatus L.), crownvetch (Coronilla varia L.), alfalfa (Medicago sativa L.), common sericea lespedeza and AULotan sericea lespedeza (Lespedeza cuneata L.), tall fescue-ladino clover, tall fescue-alfalfa, orchardgrass-birdsfoot trefoil, switchgrass-AULotan, and an herbaceous species mix intended for planting on reforested sites consisting of foxtail millet [Setaria italica (L.) Beauv.], perennial ryegrass (Lolium perenne L.), redtop (Agrostis alba L.), kobe lespedeza (Kummerowia striata L.), appalow lespedeza (Lespedeza cuneata L.), and birdsfoot trefoil were established between spring 1990 and 1991. Vegetative biomass and/or persistence were assessed in 1996, 1997, 1998, 2000, 2001, and 2002. The high rate of biosolids applied provided favorable soil chemical properties but could not overcome physical property limitations due to shallow undeveloped soil perched atop a compacted soil layer at 25 cm depth. The plant species whose persistence and biomass production were the greatest after a decade or more of establishment (i.e., switchgrass, sericea lespedeza, reed canarygrass, tall fescue, and crownvetch) shared the physiological and reproductive characteristics of low fertility requirements, drought and moisture tolerance, and propagation by rhizome and/or stolons. Of these five species, two (tall fescue and sericea lespedeza) are or have been seeded commonly on Appalachian coal surface mines, and often dominate abandoned pasture sites. Despite the high rates of heavy metal-bearing biosolids applied to the soil, plant uptake of Cd, Cu, Ni, and Zn were well within critical concentrations more than a decade after establishment of the vegetation.
Concerns over the possible increase in phytoavailability of biosolids-applied trace metals to pla... more Concerns over the possible increase in phytoavailability of biosolids-applied trace metals to plants have been raised based on the assumption that decomposition of applied organic matter would increase phytoavailability. The objectives of this study were to assess the effect of time on chemical extractability and concentration of Cd, Cu, Ni, and Zn in plants on plots established by a single application of biosolids with high trace metals content in 1984. Biosolids were applied to 1.5 by 2.3 m confined plots of a Davidson clay loam (clayey, kaolinitic, thermic Rhodic Kandiudults) at 0, 42, 84, 126, 168, and 210 Mg ha(-1). The highest biosolids application supplied 4.5, 760, 43, and 620 kg ha(-1) of Cd, Cu, Ni, and Zn, respectively. Radish (Raphanus sativus L.), romaine lettuce (Lactuca sativa L. var. longifolia), and barley (Hordeum vulgare L.) were planted at the site for 3 consecutive years, 17 to 19 yr after biosolids application. Extractable Cd, Cu, Ni, and Zn (as measured by DTPA, CaCl(2,) and Mehlich-1) were determined on 15-cm depth samples from each plot. The DTPA-extractable Cu and Zn decreased by 58 and 42%, respectively, 17 yr after application despite a significant reduction in organic matter content. Biosolids treatments had no significant effect on crop yield. Plant tissue metal concentrations increased with biosolids rate but were within the normal range of these crops. Trace metal concentrations in plants generally correlated well with the concentrations extracted from soil with DTPA, CaCl(2), and Mehlich-1. Metal concentrations in plant tissue exhibited a plateau response in most cases. The uptake coefficient values generated for the different crops were in agreement with the values set by the Part 503 Rule.
Continuous N-based application of biosolids contributes to a gradual increase of trace elements a... more Continuous N-based application of biosolids contributes to a gradual increase of trace elements and P in soils. Th e objectives of this study were to assess the accumulation and vertical transport of Cu, Zn, C, N, and P within the profi le of two coastal plain soils. Liquid (6-8% total solids) biosolids were applied to an Acredale silt loam (fi ne silty, mixed, thermic typic Ochraqualfs) and Bojac loamy sand (coarse loamy, mixed, thermic typic Hapludult) annually from 1984 to 1998. Th e repeated applications supplied 70, 204, and 3823 kg ha −1 of Cu, Zn, and P, respectively, to the Acredale and 81, 225, and 4265 kg ha −1 of Cu, Zn, and P, respectively, to the Bojac. Th e total C and N contents were not diff erent than background levels in the Bojac soil and were slightly higher in the Acredale soil 7 years after cessation of biosolids application. Phosphorus, Cu and Zn are still concentrated in the top 0.25 m of the Acredale soil. Enrichment of P, Cu, and Zn were detected to the deepest soil increment in the coarse-textured Bojac soil. Approximately 20 to 40% of the Cu and Zn applied in the biosolids could not be accounted, which was likely due to a combination of leaching and incomplete extraction. Excessive Mehlich 1-P concentrations and a high degree of P saturation were found in amended soil, raising the potential for P release to runoff or leaching water.
The effects of hay, compost, plastic and paper mulches on soil temperature, soil moisture and yie... more The effects of hay, compost, plastic and paper mulches on soil temperature, soil moisture and yield of paste tomato were evaluated on five farms in Virginia. Organic mulches reduced afternoon soil temperature and maintained higher soil moisture levels than other treatments. Black plastic mulch increased soil temperatures by 1–2°C, but sometimes resulted in lower soil moisture levels in early summer, probably by hindering penetration of rainfall. Both undyed kraft paper and black paper mulches reduced afternoon soil temperature slightly. Oiled paper initially increased afternoon soil temperature by 4°C, but this effect diminished over time. Paper mulches decomposed before the end of the season, allowing increased evaporative losses of soil moisture.Mulch treatments apparently affected early tomato yield by influencing soil temperature regime, but affected later yields by modifying soil moisture levels. Early yields were generally highest with black plastic mulch and lowest in organic mulches, with paper mulch intermediate. At sites not affected by late blight, total yields were generally: organic mulch ≥ plastic ≥ paper > unmulched. At sites affected by late blight, later-maturing fruit were lost, so that the delay in ripening in soil-cooling organic mulches resulted in a significant yield reduction compared to black plastic.
Potential contributions several mulches to soil organic matter (OM), and their effects on crop-av... more Potential contributions several mulches to soil organic matter (OM), and their effects on crop-available nitrogen (N), earthworm activity and tilth-related soil properties, were evaluated on five working vegetable farms in Virginia. A 100-mm thick hay mulch added sufficient organic carbon (C) and N to replace seasonal soil OM losses expected for temperate zone soils. Paper and plastic mulches contributed little or no OM, but mulching alleys between film-mulched beds helped replenish soil OM in these mulching systems.At one site, soil NO3-N was higher under plastic and oiled-paper mulches than under organic mulches or without mulch, probably because plastic and oiled paper reduced leaching of NO3-N. Mulch treatment did not affect soil NO3-N at other sites, and generally did not affect tomato foliar TKN, except when the treatment reduced soil moisture levels. Hay and compost mulches had C:N ratios ranging from 24 to 48, but high foliar TKN in these treatments indicated that the mulches did not reduce N availability to the crop. Mulch treatments imposed for a single growing season did not affect soil bulk density, steady state water infiltration rate or wet aggregate stability. However, earthworm populations at the end of the season were about twice as high under hay mulch as under black plastic.
Field experiments were conducted to examine the effects of organic and synthetic soil fertility a... more Field experiments were conducted to examine the effects of organic and synthetic soil fertility amendments on soil microbial communities and soil physical and chemical properties at three organic and three conventional vegetable farms in Virginia and Maryland in 1996 and 1997. Two treatments, including either an alternative organic soil amendment (composted cotton-gin trash, composted yard waste, or cattle manure) or synthetic soil amendment (fertilizer) were applied to three replicated plots at each grower field location. Production history and time affected propagule densities of Trichoderma species which remained higher in soils from organic farms. Propagule densities of Trichoderma species, thermophilic microorganisms, and enteric bacteria were also detected in greater numbers in soils amended with alternative than synthetic amendments, whereas propagule densities of Phytophthora and Pythium species were lower in soils amended with alternative than synthetic fertility amendments. Concentrations of Ca, K, Mg, and Mn were higher in soils amended with alternative than synthetic fertility amendments. Canonical correlations and principle component analyses indicated significant correlation between these soil chemical factors and the biological communities. First-order canonical correlations were more negative in fields with a conventional history, and use of synthetic fertilizers, whereas canonical correlations were more positive in fields with a history of organic production and alternative soil amendments. In the first year, yields of corn or melon were not different in soil amended with either synthetic or organic amendments at four of six farms. In the second year, when all growers planted tomatoes, yields were higher on farms with a history of organic production, regardless of soil amendment type. Alternative fertility amendments, enhanced beneficial soil microorganisms reduced pathogen populations, increased soil organic matter, total carbon, and cation exchange capacity (CEC), and lowered bulk density thus improving soil quality.
Communications in Soil Science and Plant Analysis, 1997
The presidedress soil nitrate test (PSNT) and the presidedress tissue nitrogen test (PTNT) have b... more The presidedress soil nitrate test (PSNT) and the presidedress tissue nitrogen test (PTNT) have been developed to assess residual soil nitrogen (N) sufficiency for corn (Zea mays L.) in the humid eastern U.S. We conducted field studies at 47 sites during 1990 and 1991 to evaluate the use of the PSNT and PTNT for corn in Coastal Plain, Piedmont, and Appalachian Ridge and Valley regions of Virginia. Seven rates of fertilizer N (0, 45, 90, 135, 180, 225, and 270 kg/ha) were applied at corn height of 0.40 to 0.50 m and replicated four times in a randomized complete block design. Whole corn plants and soil to a depth of 0.30 m were sampled when corn height was 0.15 to 0.30 m to estimate available soil N prior to the application of fertilizer N treatments. Corn grain yield response to fertilizer N was used to assess residual soil N availability. Nitrogen concentration of whole corn plants at 0.15 to 0.30 m height was not an accurate indicator of plant-available soil N. Corn yields were maximized without sidedress N at the 19 sites where soil NO 3 -N was at least 18 mg-kg -1 and at the 17 sites where soil (NO 3 +NH 4 )-N was at least 22 mg-kg -1 . The PSNT predicted corn N sufficiency regardless of soil physiographic region or surface texture; however, the critical values for NO 3 -N and (NO 3 +NH 4 )-N were 3 to 5 mg-kg -1 lower than those established in Pennsylvania and Maryland, where cooler soil temperatures may permit greater residence time of inorganic N.
Increasing amounts of animal and municipal wastes are being composted before land application to ... more Increasing amounts of animal and municipal wastes are being composted before land application to improve handling and spreading characteristics, and to reduce odor and disease incidence. Repeated applications of composted biosolids and manure to cropland may increase the risk for P enrichment of agricultural runoff. We conducted field research in 2003 and 2004 on a Fauquier silty clay loam (Ultic Hapludalfs) to compare the effects of annual (since 1999) applications of composted and uncomposted organic residuals on P runoff characteristics. Biosolids compost (BSC), poultry litter-yard waste compost (PLC), and uncomposted poultry litter (PL) were applied based on estimated plant-available N. A commercial fertilizer treatment (CF) and an unamended control treatment (CTL) were also included. Corn (Zea mays L.) and a cereal rye (Secale cereal L.) cover crop were planted each year. We applied simulated rainfall in fall 2004 and analyzed runoff for dissolved reactive P (DRP), total dissolved P (TDP), total P (TP), total organic C (TOC), and total suspended solids (TSS). End of season soil samples were analyzed for Mehlich-3 P (M3P), EPA 3050 P (3050P), water soluble P (WSP), degree of P saturation (DPS), soil C, and bulk density. Compost treatments significantly increased soil C, decreased bulk density, and increased M3P, 3050P, WSP, and DPS. The concentration of DRP, TDP, and TP in runoff was highest in compost treatments, but the mass of DRP and TDP was not different among treatments because infiltration was higher and runoff lower in compostamended soil. Improved soil physical properties associated with poultry litter-yard waste compost application decreased loss of TP and TSS.
Deep row incorporation of biosolids is an alternative land application method that may allow high... more Deep row incorporation of biosolids is an alternative land application method that may allow higher than currently permitted mine land reclamation application rates. Biosolids treated by various processes possess characteristics that uniquely affect metal solubility and mobility due to their influence on metal speciation. The objectives of this research were to compare the effects of biosolids stabilization type and rate on heavy metal solubility, mobility, and speciation. Two rates each of Alexandria, (Virginia) anaerobically digested (213 and 426 dry Mg ha -1 ) and Blue Plains (Washington, DC) lime-stabilized (329 and 657 dry Mg ha -1 ) biosolids were placed in trenches at a mineral sands mine reclamation site in Dinwiddie County, Virginia in June and July 2006. Vertical and lateral transport of heavy metals from the biosolids seams were determined by analyzing leachate collected in zero tension lysimeters below the trenches and suction lysimeters adjacent to the trenches. Chloride (Cl -), sulfate (SO 4 2-
Past research indicates that created non-tidal wetlands in the mid-Atlantic region are considerab... more Past research indicates that created non-tidal wetlands in the mid-Atlantic region are considerably lower in soil organic matter than native forested hydric soils. However, optimal loading rates for created wetland soil reconstruction have not been rigorously established. Our objective was to determine appropriate organic amendment loading rates for a Coastal Plain mitigation wetland based on 1) soil properties reflective of hydric soil development, 2) the formation of redoximorphic features, and 3) the growth and vigor of hydrophytic vegetation. The study contained wet (CCW-Wet) and dry (CCW-Dry) experiments, each receiving 6 compost treatments (0 Mg/ha untilled and 0, 56, 112, 224, and 336 Mg/ha tilled). Over the 1.5-year monitoring period, redox potential decreased and redoximorphic feature formation increased with compost loadings up to 112 Mg/ha. Surface bulk density decreased with loadings up to 224 Mg/ha, while no treatment differences were noted in sub-surface bulk density. In the CCW-Dry experiment, soil moisture peaked in the 224 Mg/ha treatment, while soil moisture in CCW-Wet increased consistently across all loadings. Total biomass in CCW-Wet and Betula nigra L. growth in both experiments increased with loading rate. Total biomass in CCW-Dry and Quercus palustris Muench. growth in both experiments peaked at 112
This paper will present collective results of 25 years of research by the authors into the use of... more This paper will present collective results of 25 years of research by the authors into the use of municipal biosolids (sewage sludge) and other residuals to reclaim sites disturbed by a range of mining and construction activities. Loading rate experiments and demonstrations have been conducted on areas drastically disturbed by coal mining, sand mining, heavy mineral mining, urbanization, airport construction and heavy metal processing. At all sites, the post-mining soils were devoid of organic matter, very low in nutrients and frequently quite acidic. At all sites, addition of biosolids at higher than agronomic rates resulted in complete stabilization of the resultant mine soils and vigorous stable vegetation that persisted for > 5 years and has allowed enhanced invasion of native herbaceous species. Application of higher rates is not compatible with establishment of certain native tree species (e.g. Pinus sp.), however, due to adverse effects of soluble salts, nutrient enrichment and enhanced competition by grasses. An underlying goal of this program has been to develop approaches that use higher than agronomic rates of biosolids while simultaneously minimizing losses of N and P to local ground- and surface-waters. In the early 1980's, working on USA coal mining spoils, we determined that that approximately 100 Mg/ha of secondary cake biosolids was optimal for revegetation with herbaceous species, but water quality monitoring was not a concern at that time. This finding raised concerns, however, that the large amounts of total N applied (> 2500 kg/ha) would lead to nitrate-N contamination of local waters. Subsequent work in the early 1990's indicated that similar rates of biosolids could be mixed with woodchips (high palatable C source) and land-applied to large (> 100 ha) coal mining sites with no losses of nitrate-N to surface or ground-water due to microbial immobilization of the applied N. Follow-up work at three sand mining (sand & gravel and mineral sands) sites in eastern Virginia indicated that non C-amended biosolids could be applied at loading rates of up to 75 Mg/ha without significant local ground-water effects, but that significant elevation of nitrate-N in shallow root-zone (75 cm) percolates was observed the first winter after application. Addition of palatable C (as sawdust) to adjust the applied biosolids C:N ratio to 25:1 significantly reduced nitrate-N in root-zone percolates and would allow for higher loading rates where indicated. Lime-stabilized biosolids (100 Mg/ha; 15 to 25% CCE) have also been used to permanently stabilize and revegetate large areas (> 100 ha) acid-sulfate (pH < 3.5) soils disturbed by construction in eastern Virginia with minimal local water quality effects. Parallel studies at our sites in the USA have indicated no significant heavy metal leaching or plant uptake risks as long as sludge quality and soil pH are controlled. Finally, long-term (10 yr) results from Katowice, Poland, indicate that high rates (> 250 Mg/ha) of biosolids co-applied with waste limes can be utilized to permanently stabilize and revegetate a wide range of phytotoxic and heavily contaminated Pb/Zn smelter slags and processing tailings. Biosolids are generally available at very low cost for land rehabilitation since their cost of transport and application is usually born by the producer or source municipality. Their use is particularly cost-effective when lime-stabilized materials are applied to strongly acidic or metalliferous sites.
The long-term mobility of trace metals has been cited as a potential hazard by critics of EPA 503... more The long-term mobility of trace metals has been cited as a potential hazard by critics of EPA 503 rule governing the land application of biosolids. The objectives of this study were to assess the accumulation of Cu, Ni, Cd, and Zn within the soil profile; the distribution of exchangeable, specifically adsorbed, organic, and oxide fractions of each metal; and mass balance of Cu, Ni, and Zn 17 yr after a single biosolids application. Biosolids were applied to 1.5- x 2.3-m confined plots of a Davidson clay loam (fine, kaolinitic, thermic Rhodic Kandiudult) in 1984 at 0, 42, 84, 126, 168, and 210 Mg ha(-1). The highest biosolids application supplied 4.5, 750, 43, and 600 kg ha(-1) of Cd, Cu, Ni, and Zn, respectively. Soils were sampled to a depth of 0.9 m and sectioned into 5-cm increments after separating the Ap horizon. Total (EPA-3050B), bioavailable (Mehlich-I), sequential extraction, and dispersible clay analyses were performed on samples from the control, 126 Mg ha(-1), and 210 Mg ha(-1) treatments. Trace metals are still concentrated in the top 0.2 m with slight enrichment down to 0.3 m. More than 85% of applied Cu, Ni, and Zn are still found in the topsoil where biosolids was incorporated and 95% or more of the applied metals were accounted for with mass balance calculations. Mehlich-I results showed a slight increase in metal concentration down to 0.35 m. Biosolids application increased the concentrations of trace metals in all the extracted fractions. The major portions of Cu, Zn, and Ni are associated with the metal-oxides fraction. Dispersible clay content and water-soluble metal contents were low and except for water-soluble Zn they were not affected by biosolids application. Results from this study showed that 17 yr after biosolids application there was negligible movement of trace metals through the soil profile and consequently there is little risk of contamination of ground water at this site.
The selection of plant species is critical for the successful establishment and long-term mainten... more The selection of plant species is critical for the successful establishment and long-term maintenance of vegetation on reclaimed surface mined soils. A study was conducted to assess the capability of 16 forage grass and legume species in monocultures and mixes to establish and thrive on a reclaimed Appalachian surface mine amended with biosolids. The 0.15-ha coarse-textured, rocky, non-acid forming mined site was prepared for planting by grading to a 2% slope and amending sandstone overburden materials with a mixture of composted and dewatered, anaerobically digested biosolids at a rate of 368 Mg ha(-1) (dry weight). Tall fescue (Festuca arundinacea Schreb.), orchardgrass (Dactylis glomerata L.), switchgrass (Panicum virgatum L.), caucasian bluestem (Bothriochloa caucasia L.), reed canarygrass (Phalaris arundinacea L.), ladino clover (Trifolium repens L.), birdsfoot trefoil (Lotus corniculatus L.), crownvetch (Coronilla varia L.), alfalfa (Medicago sativa L.), common sericea lespedeza and AULotan sericea lespedeza (Lespedeza cuneata L.), tall fescue-ladino clover, tall fescue-alfalfa, orchardgrass-birdsfoot trefoil, switchgrass-AULotan, and an herbaceous species mix intended for planting on reforested sites consisting of foxtail millet [Setaria italica (L.) Beauv.], perennial ryegrass (Lolium perenne L.), redtop (Agrostis alba L.), kobe lespedeza (Kummerowia striata L.), appalow lespedeza (Lespedeza cuneata L.), and birdsfoot trefoil were established between spring 1990 and 1991. Vegetative biomass and/or persistence were assessed in 1996, 1997, 1998, 2000, 2001, and 2002. The high rate of biosolids applied provided favorable soil chemical properties but could not overcome physical property limitations due to shallow undeveloped soil perched atop a compacted soil layer at 25 cm depth. The plant species whose persistence and biomass production were the greatest after a decade or more of establishment (i.e., switchgrass, sericea lespedeza, reed canarygrass, tall fescue, and crownvetch) shared the physiological and reproductive characteristics of low fertility requirements, drought and moisture tolerance, and propagation by rhizome and/or stolons. Of these five species, two (tall fescue and sericea lespedeza) are or have been seeded commonly on Appalachian coal surface mines, and often dominate abandoned pasture sites. Despite the high rates of heavy metal-bearing biosolids applied to the soil, plant uptake of Cd, Cu, Ni, and Zn were well within critical concentrations more than a decade after establishment of the vegetation.
Concerns over the possible increase in phytoavailability of biosolids-applied trace metals to pla... more Concerns over the possible increase in phytoavailability of biosolids-applied trace metals to plants have been raised based on the assumption that decomposition of applied organic matter would increase phytoavailability. The objectives of this study were to assess the effect of time on chemical extractability and concentration of Cd, Cu, Ni, and Zn in plants on plots established by a single application of biosolids with high trace metals content in 1984. Biosolids were applied to 1.5 by 2.3 m confined plots of a Davidson clay loam (clayey, kaolinitic, thermic Rhodic Kandiudults) at 0, 42, 84, 126, 168, and 210 Mg ha(-1). The highest biosolids application supplied 4.5, 760, 43, and 620 kg ha(-1) of Cd, Cu, Ni, and Zn, respectively. Radish (Raphanus sativus L.), romaine lettuce (Lactuca sativa L. var. longifolia), and barley (Hordeum vulgare L.) were planted at the site for 3 consecutive years, 17 to 19 yr after biosolids application. Extractable Cd, Cu, Ni, and Zn (as measured by DTPA, CaCl(2,) and Mehlich-1) were determined on 15-cm depth samples from each plot. The DTPA-extractable Cu and Zn decreased by 58 and 42%, respectively, 17 yr after application despite a significant reduction in organic matter content. Biosolids treatments had no significant effect on crop yield. Plant tissue metal concentrations increased with biosolids rate but were within the normal range of these crops. Trace metal concentrations in plants generally correlated well with the concentrations extracted from soil with DTPA, CaCl(2), and Mehlich-1. Metal concentrations in plant tissue exhibited a plateau response in most cases. The uptake coefficient values generated for the different crops were in agreement with the values set by the Part 503 Rule.
Continuous N-based application of biosolids contributes to a gradual increase of trace elements a... more Continuous N-based application of biosolids contributes to a gradual increase of trace elements and P in soils. Th e objectives of this study were to assess the accumulation and vertical transport of Cu, Zn, C, N, and P within the profi le of two coastal plain soils. Liquid (6-8% total solids) biosolids were applied to an Acredale silt loam (fi ne silty, mixed, thermic typic Ochraqualfs) and Bojac loamy sand (coarse loamy, mixed, thermic typic Hapludult) annually from 1984 to 1998. Th e repeated applications supplied 70, 204, and 3823 kg ha −1 of Cu, Zn, and P, respectively, to the Acredale and 81, 225, and 4265 kg ha −1 of Cu, Zn, and P, respectively, to the Bojac. Th e total C and N contents were not diff erent than background levels in the Bojac soil and were slightly higher in the Acredale soil 7 years after cessation of biosolids application. Phosphorus, Cu and Zn are still concentrated in the top 0.25 m of the Acredale soil. Enrichment of P, Cu, and Zn were detected to the deepest soil increment in the coarse-textured Bojac soil. Approximately 20 to 40% of the Cu and Zn applied in the biosolids could not be accounted, which was likely due to a combination of leaching and incomplete extraction. Excessive Mehlich 1-P concentrations and a high degree of P saturation were found in amended soil, raising the potential for P release to runoff or leaching water.
The effects of hay, compost, plastic and paper mulches on soil temperature, soil moisture and yie... more The effects of hay, compost, plastic and paper mulches on soil temperature, soil moisture and yield of paste tomato were evaluated on five farms in Virginia. Organic mulches reduced afternoon soil temperature and maintained higher soil moisture levels than other treatments. Black plastic mulch increased soil temperatures by 1–2°C, but sometimes resulted in lower soil moisture levels in early summer, probably by hindering penetration of rainfall. Both undyed kraft paper and black paper mulches reduced afternoon soil temperature slightly. Oiled paper initially increased afternoon soil temperature by 4°C, but this effect diminished over time. Paper mulches decomposed before the end of the season, allowing increased evaporative losses of soil moisture.Mulch treatments apparently affected early tomato yield by influencing soil temperature regime, but affected later yields by modifying soil moisture levels. Early yields were generally highest with black plastic mulch and lowest in organic mulches, with paper mulch intermediate. At sites not affected by late blight, total yields were generally: organic mulch ≥ plastic ≥ paper > unmulched. At sites affected by late blight, later-maturing fruit were lost, so that the delay in ripening in soil-cooling organic mulches resulted in a significant yield reduction compared to black plastic.
Potential contributions several mulches to soil organic matter (OM), and their effects on crop-av... more Potential contributions several mulches to soil organic matter (OM), and their effects on crop-available nitrogen (N), earthworm activity and tilth-related soil properties, were evaluated on five working vegetable farms in Virginia. A 100-mm thick hay mulch added sufficient organic carbon (C) and N to replace seasonal soil OM losses expected for temperate zone soils. Paper and plastic mulches contributed little or no OM, but mulching alleys between film-mulched beds helped replenish soil OM in these mulching systems.At one site, soil NO3-N was higher under plastic and oiled-paper mulches than under organic mulches or without mulch, probably because plastic and oiled paper reduced leaching of NO3-N. Mulch treatment did not affect soil NO3-N at other sites, and generally did not affect tomato foliar TKN, except when the treatment reduced soil moisture levels. Hay and compost mulches had C:N ratios ranging from 24 to 48, but high foliar TKN in these treatments indicated that the mulches did not reduce N availability to the crop. Mulch treatments imposed for a single growing season did not affect soil bulk density, steady state water infiltration rate or wet aggregate stability. However, earthworm populations at the end of the season were about twice as high under hay mulch as under black plastic.
Field experiments were conducted to examine the effects of organic and synthetic soil fertility a... more Field experiments were conducted to examine the effects of organic and synthetic soil fertility amendments on soil microbial communities and soil physical and chemical properties at three organic and three conventional vegetable farms in Virginia and Maryland in 1996 and 1997. Two treatments, including either an alternative organic soil amendment (composted cotton-gin trash, composted yard waste, or cattle manure) or synthetic soil amendment (fertilizer) were applied to three replicated plots at each grower field location. Production history and time affected propagule densities of Trichoderma species which remained higher in soils from organic farms. Propagule densities of Trichoderma species, thermophilic microorganisms, and enteric bacteria were also detected in greater numbers in soils amended with alternative than synthetic amendments, whereas propagule densities of Phytophthora and Pythium species were lower in soils amended with alternative than synthetic fertility amendments. Concentrations of Ca, K, Mg, and Mn were higher in soils amended with alternative than synthetic fertility amendments. Canonical correlations and principle component analyses indicated significant correlation between these soil chemical factors and the biological communities. First-order canonical correlations were more negative in fields with a conventional history, and use of synthetic fertilizers, whereas canonical correlations were more positive in fields with a history of organic production and alternative soil amendments. In the first year, yields of corn or melon were not different in soil amended with either synthetic or organic amendments at four of six farms. In the second year, when all growers planted tomatoes, yields were higher on farms with a history of organic production, regardless of soil amendment type. Alternative fertility amendments, enhanced beneficial soil microorganisms reduced pathogen populations, increased soil organic matter, total carbon, and cation exchange capacity (CEC), and lowered bulk density thus improving soil quality.
Communications in Soil Science and Plant Analysis, 1997
The presidedress soil nitrate test (PSNT) and the presidedress tissue nitrogen test (PTNT) have b... more The presidedress soil nitrate test (PSNT) and the presidedress tissue nitrogen test (PTNT) have been developed to assess residual soil nitrogen (N) sufficiency for corn (Zea mays L.) in the humid eastern U.S. We conducted field studies at 47 sites during 1990 and 1991 to evaluate the use of the PSNT and PTNT for corn in Coastal Plain, Piedmont, and Appalachian Ridge and Valley regions of Virginia. Seven rates of fertilizer N (0, 45, 90, 135, 180, 225, and 270 kg/ha) were applied at corn height of 0.40 to 0.50 m and replicated four times in a randomized complete block design. Whole corn plants and soil to a depth of 0.30 m were sampled when corn height was 0.15 to 0.30 m to estimate available soil N prior to the application of fertilizer N treatments. Corn grain yield response to fertilizer N was used to assess residual soil N availability. Nitrogen concentration of whole corn plants at 0.15 to 0.30 m height was not an accurate indicator of plant-available soil N. Corn yields were maximized without sidedress N at the 19 sites where soil NO 3 -N was at least 18 mg-kg -1 and at the 17 sites where soil (NO 3 +NH 4 )-N was at least 22 mg-kg -1 . The PSNT predicted corn N sufficiency regardless of soil physiographic region or surface texture; however, the critical values for NO 3 -N and (NO 3 +NH 4 )-N were 3 to 5 mg-kg -1 lower than those established in Pennsylvania and Maryland, where cooler soil temperatures may permit greater residence time of inorganic N.
Increasing amounts of animal and municipal wastes are being composted before land application to ... more Increasing amounts of animal and municipal wastes are being composted before land application to improve handling and spreading characteristics, and to reduce odor and disease incidence. Repeated applications of composted biosolids and manure to cropland may increase the risk for P enrichment of agricultural runoff. We conducted field research in 2003 and 2004 on a Fauquier silty clay loam (Ultic Hapludalfs) to compare the effects of annual (since 1999) applications of composted and uncomposted organic residuals on P runoff characteristics. Biosolids compost (BSC), poultry litter-yard waste compost (PLC), and uncomposted poultry litter (PL) were applied based on estimated plant-available N. A commercial fertilizer treatment (CF) and an unamended control treatment (CTL) were also included. Corn (Zea mays L.) and a cereal rye (Secale cereal L.) cover crop were planted each year. We applied simulated rainfall in fall 2004 and analyzed runoff for dissolved reactive P (DRP), total dissolved P (TDP), total P (TP), total organic C (TOC), and total suspended solids (TSS). End of season soil samples were analyzed for Mehlich-3 P (M3P), EPA 3050 P (3050P), water soluble P (WSP), degree of P saturation (DPS), soil C, and bulk density. Compost treatments significantly increased soil C, decreased bulk density, and increased M3P, 3050P, WSP, and DPS. The concentration of DRP, TDP, and TP in runoff was highest in compost treatments, but the mass of DRP and TDP was not different among treatments because infiltration was higher and runoff lower in compostamended soil. Improved soil physical properties associated with poultry litter-yard waste compost application decreased loss of TP and TSS.
Deep row incorporation of biosolids is an alternative land application method that may allow high... more Deep row incorporation of biosolids is an alternative land application method that may allow higher than currently permitted mine land reclamation application rates. Biosolids treated by various processes possess characteristics that uniquely affect metal solubility and mobility due to their influence on metal speciation. The objectives of this research were to compare the effects of biosolids stabilization type and rate on heavy metal solubility, mobility, and speciation. Two rates each of Alexandria, (Virginia) anaerobically digested (213 and 426 dry Mg ha -1 ) and Blue Plains (Washington, DC) lime-stabilized (329 and 657 dry Mg ha -1 ) biosolids were placed in trenches at a mineral sands mine reclamation site in Dinwiddie County, Virginia in June and July 2006. Vertical and lateral transport of heavy metals from the biosolids seams were determined by analyzing leachate collected in zero tension lysimeters below the trenches and suction lysimeters adjacent to the trenches. Chloride (Cl -), sulfate (SO 4 2-
Past research indicates that created non-tidal wetlands in the mid-Atlantic region are considerab... more Past research indicates that created non-tidal wetlands in the mid-Atlantic region are considerably lower in soil organic matter than native forested hydric soils. However, optimal loading rates for created wetland soil reconstruction have not been rigorously established. Our objective was to determine appropriate organic amendment loading rates for a Coastal Plain mitigation wetland based on 1) soil properties reflective of hydric soil development, 2) the formation of redoximorphic features, and 3) the growth and vigor of hydrophytic vegetation. The study contained wet (CCW-Wet) and dry (CCW-Dry) experiments, each receiving 6 compost treatments (0 Mg/ha untilled and 0, 56, 112, 224, and 336 Mg/ha tilled). Over the 1.5-year monitoring period, redox potential decreased and redoximorphic feature formation increased with compost loadings up to 112 Mg/ha. Surface bulk density decreased with loadings up to 224 Mg/ha, while no treatment differences were noted in sub-surface bulk density. In the CCW-Dry experiment, soil moisture peaked in the 224 Mg/ha treatment, while soil moisture in CCW-Wet increased consistently across all loadings. Total biomass in CCW-Wet and Betula nigra L. growth in both experiments increased with loading rate. Total biomass in CCW-Dry and Quercus palustris Muench. growth in both experiments peaked at 112
This paper will present collective results of 25 years of research by the authors into the use of... more This paper will present collective results of 25 years of research by the authors into the use of municipal biosolids (sewage sludge) and other residuals to reclaim sites disturbed by a range of mining and construction activities. Loading rate experiments and demonstrations have been conducted on areas drastically disturbed by coal mining, sand mining, heavy mineral mining, urbanization, airport construction and heavy metal processing. At all sites, the post-mining soils were devoid of organic matter, very low in nutrients and frequently quite acidic. At all sites, addition of biosolids at higher than agronomic rates resulted in complete stabilization of the resultant mine soils and vigorous stable vegetation that persisted for > 5 years and has allowed enhanced invasion of native herbaceous species. Application of higher rates is not compatible with establishment of certain native tree species (e.g. Pinus sp.), however, due to adverse effects of soluble salts, nutrient enrichment and enhanced competition by grasses. An underlying goal of this program has been to develop approaches that use higher than agronomic rates of biosolids while simultaneously minimizing losses of N and P to local ground- and surface-waters. In the early 1980's, working on USA coal mining spoils, we determined that that approximately 100 Mg/ha of secondary cake biosolids was optimal for revegetation with herbaceous species, but water quality monitoring was not a concern at that time. This finding raised concerns, however, that the large amounts of total N applied (> 2500 kg/ha) would lead to nitrate-N contamination of local waters. Subsequent work in the early 1990's indicated that similar rates of biosolids could be mixed with woodchips (high palatable C source) and land-applied to large (> 100 ha) coal mining sites with no losses of nitrate-N to surface or ground-water due to microbial immobilization of the applied N. Follow-up work at three sand mining (sand & gravel and mineral sands) sites in eastern Virginia indicated that non C-amended biosolids could be applied at loading rates of up to 75 Mg/ha without significant local ground-water effects, but that significant elevation of nitrate-N in shallow root-zone (75 cm) percolates was observed the first winter after application. Addition of palatable C (as sawdust) to adjust the applied biosolids C:N ratio to 25:1 significantly reduced nitrate-N in root-zone percolates and would allow for higher loading rates where indicated. Lime-stabilized biosolids (100 Mg/ha; 15 to 25% CCE) have also been used to permanently stabilize and revegetate large areas (> 100 ha) acid-sulfate (pH < 3.5) soils disturbed by construction in eastern Virginia with minimal local water quality effects. Parallel studies at our sites in the USA have indicated no significant heavy metal leaching or plant uptake risks as long as sludge quality and soil pH are controlled. Finally, long-term (10 yr) results from Katowice, Poland, indicate that high rates (> 250 Mg/ha) of biosolids co-applied with waste limes can be utilized to permanently stabilize and revegetate a wide range of phytotoxic and heavily contaminated Pb/Zn smelter slags and processing tailings. Biosolids are generally available at very low cost for land rehabilitation since their cost of transport and application is usually born by the producer or source municipality. Their use is particularly cost-effective when lime-stabilized materials are applied to strongly acidic or metalliferous sites.
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