Ashlee L.D. Dere

Natural and anthropogenic processes contributing to metal enrichment in surface soils of central Pennsylvania

Metals in soils may positively or negatively affect plants as well as soil micro-organisms and mesofauna, depending on their abundance and bioavailability. Atmospheric deposition and biological uplift commonly result in metal enrichment in surface soils, but the relative importance of these processes is not always resolved. Here, we used an integrated approach to study the cycling of phosphorus and a suite of metals from the soil to the canopy (and back) in a temperate watershed. The behavior of elements in these surface soils fell into three categories. First, Al, Fe, V, Co, and Cr showed little to no enrichment in the top soil layers, and their concentrations were determined primarily by soil production fluxes with little influence of either atmospheric inputs or biological activity. Second, P, Cu, Zn and Cd were moderately enriched in surface soils due to a combination of atmospheric deposition and biological uplift. Among the metals we studied, Cu, Zn and Cd concentrations in surface soils were the most sensitive to changes in atmospheric deposition fluxes. Finally, Mo and Mn showed strong enrichment in the top soil layer that could not be explained strictly by either current atmospheric deposition or biological recycling processes, but may reflect both their unique chemistry and remnants of past anthropogenic fluxes. Mn has a long residence time in the soil partly due to intense biological uplift that retains Mn in the top soil layer. Mo, in spite of the high solubility of molybdate, remains in the soil because of strong binding to natural organic matter. This study demonstrates the need to consider simultaneously the vegetation and the soils to understand elemental distribution within soil profiles as well as cycling within watersheds.

Nutrient leaching and soil retention in mined land reclaimed with stabilized manure.

Two environmental problems in Pennsylvania are degraded mined lands and excess manure nutrients from intensive animal production. Manure could be used in mine reclamation, but the large application rates required for sustained biomass production could result in significant nutrient discharge. An abandoned mine site in Schuylkill County, Pennsylvania, was used to test manure nutrient stabilization by composting and by mixing with primary paper mill sludge (PMS). Reclamation treatments were lime and fertilizer, composted poultry manure (78 and 156 Mg ha), and poultry manure (50 Mg ha) mixed with PMS (103 and 184 Mg ha) to achieve C-to-N ratios of 20 and 29. Leachates were collected with zero-tension lysimeters, and during 3 yr following amendment application, <1% of added N leached from the compost treatments. The manure+PMS C:N 29 treatment leached more N than any other treatment (393 kg N ha during 3 yr, 12.4 times more N than compost treatments), mostly as pulses of NO in the first two fall seasons following reclamation. The manure+PMS C:N 20 treatment leached 107 kg N ha during 3 yr. Three years after amendment application, most of the N and P added with the manure-based amendments was retained in the mine soil even though net immobilization of N by PMS appeared to be limited to 3 mo following application. Composting or mixing PMS with manure to achieve a C-to-N ratio of 20 can effectively minimize N leaching, retain added N in mine soil, and provide greater improvement in soil quality than lime and fertilizer amendment.

Nutrient Leaching and Switchgrass Growth in Mine Soil Columns Amended With Poultry Manure

In Pennsylvania, land disturbance from 150 years of extensive coal mining and intensive animal production that produces manure nutrients in excess of crop needs have degraded ecosystems and water quality. Excess manure could be used in mine reclamation, but the large application rates required for successful revegetation could result in significant nutrient discharge. This greenhouse experiment investigated two approaches to minimizing the potential for nutrient leaching of poultry layer manure used for mine reclamation: composting and C:N ratio adjustment. Columns of mine soil were amended with manure only, manure mixed with short-fiber paper mill sludge (C:N ratios of 20-40) and three rates of composted manure. Mine soil was planted with switchgrass (Panicum virgatum L.) to test biomass production of this potential biofuel, and columns were periodically leached and biomass was harvested during the 8-month experiment. Amendment with manure only resulted in the largest leaching of NO3--N (192 mg column−1) and P (12 mg column−1), whereas nutrient leaching from compost-amended soil was less than or equal to 1.67 mg NO3--N and 3.38 mg P column−1. Each level of compost addition increased switchgrass growth compared with unamended soil, and mine soil amended with manure and paper mill sludge further increased switchgrass growth while decreasing cumulative NO3- and P leaching compared with manure alone. Although composting manure was most effective at limiting nutrient leaching, our results demonstrate that coapplication of manure with a high carbon material could provide superior biomass production on mine soil while also controlling nutrient loss via leaching.ABBREVIATIONS: AML: abandoned mined land; PMS: paper mill sludge; ICP-AES: inductively coupled plasma atomic emission spectrophotometer.

NUTRIENT FLUXES FROM ABANDONED MINE SOILS RECLAIMED WITH POULTRY MANURE AND PAPER MILL SLUDGE 1

In the Mid-Atlantic region of the United States, intensive animal production generates manure nutrients in excess of crop needs, increasing the likelihood of transport to water bodies and degradation of ecosystems and water quality. In this same region, 150 years of extensive coal mining has severely degraded land and impaired streams. Excess manure could be utilized in mine reclamation, but the large application rates required for successful revegetation could result in significant nutrient discharge. A preliminary greenhouse study determined that composting or adding organic carbon to poultry layer manure greatly reduced nutrient leaching. Based on these results, a field reclamation study was established on a surface coal mine in Schuylkill County, Pennsylvania in April 2006. Treatments include a lime and fertilizer control, two rates of composted poultry layer manure (78 and 156 Mg ha -1 dry weight), and two blends of fresh poultry manure (60 Mg ha -1 dry weight) mixed with paper mill sludge (90 and 170 Mg ha -1 ) to achieve C:N ratios of 20:1 and 30:1. Leachate was collected after every rain event using pan lysimeters located 30 cm below each treatment. Leachate analysis showed a pulse of NO3 - -N from the two rates of poultry manure and paper mill sludge blends (170 and 156 mg N L -1 ) occurred three months following application. Compost treatments showed no such pulse. Cumulative N losses were greatest in the manure/paper mill sludge blends, but the control retained the least amount of original added N. An initial pulse of phosphate (5.8 mg P L -1 ) from the control treatment was observed within the first month after application. Subsequently, all treatments show minimal leaching of P (less than 1.0 mg P L -1 ). This research supports that amending mine soils with either composted poultry layer manure or fresh manure mixed with paper mill sludge are effective strategies to facilitate establishment of sustained vegetative cover on mined lands. Composted poultry manure is superior at controlling N and P loss.