Carbon and Nitrogen Dynamics in Mine Soils Reclaimed with Poultry Manure

Open Access
Author:
Dere, Ashlee Laura
Graduate Program:
Soil Science
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
April 10, 2009
Committee Members:
  • Richard Charles Stehouwer, Thesis Advisor
Keywords:
  • compost
  • switchgrass
  • revegetation
  • C:N ratios
  • phosphorus
Abstract:
In Pennsylvania, 150 years of extensive coal mining has left an estimated 250,000 acres of severely degraded mined land and impaired streams. In the same region, concentrated animal production facilities produce manure in excess of crop needs, creating an increased risk of nutrient pollution in surface and groundwater. Excess poultry manure could be used in mine reclamation, but the large application rates required for successful revegetation could result in significant nutrient discharge. Furthermore, abandoned mine lands could be used to grow switchgrass (Panicum virgatum L.), a biofuel crop, to return these lands to productivity. To achieve high production rates, however, significant and sustained nutrient levels are necessary. The goal of this research is to identify how poultry manure could be used on abandoned mine lands to ameliorate soil phytotoxicity, minimize nutrient losses, sequester nutrients and produce high switchgrass yields. Greenhouse, lab and field studies were designed to test two different methods of using poultry manure, composting and C:N ratio adjustment, to achieve this goal. In a greenhouse experiment, columns of mine soil were amended with fresh manure, manure mixed with short fiber paper mill sludge (C:N ratios of 20 - 40) and 3 rates of composted manure and leached every four weeks to assess leaching loss of macronutrients and switchgrass growth. Fresh manure exhibited the highest leaching of NO3¯– N (192 mg column-1); increasing the C:N ratio to 30:1 resulted in a five-fold decrease in the amount of NO3 leached. All compost treatments leached less than 6% of added N despite large application rates. Less than 2% of added P was leached from all treatments, indicating no significant risk of P leaching loss. There was a linear increase in switchgrass growth with each level of compost addition fresh with paper mill sludge. These results confirmed the idea that poultry manure N losses could be minimized by C:N adjustment and produce more switchgrass than lime and fertilizer amended soils. A lab incubation experiment maximized N mineralization to determine stable and labile N and C pools associated with various treatments, which included lime plus fertilizer, two rates of composted poultry manure and two blends of fresh poultry layer manure mixed with paper mill sludge with C:N ratios of 20:1 and 30:1. These treatments were incubated immediately following amendment application (year one) and one year after field application (year two). In both incubations, organic treatments were more effective at building large stable N and C pools compared to lime plus fertilizer, confirming that both methods of C:N adjustment are effective at retaining N and C and are significantly greater than N and C pools associated with inorganic fertilizer. Manure and paper mill sludge, however, had more microbial biomass after two years, which could translate to enhanced, long-term nutrient cycling. There was no measured benefit of additional carbon added with the 30:1 C:N adjustment. A field experiment using the same treatments as the lab incubation confirmed that both C:N adjustment methods work equally well to revegetate the mine soil and eliminate phytotoxic conditions. Leaching losses from composts were <1% of added N, while manure and paper mill sludge lost 8% and 16% of added N with a 20:1 and 30:1 C:N ratio, respectively. Organic treatments sequestered greater C and N in soil compared to lime plus fertilizer. Although revegetation was successful for all treatments, manure and paper mill sludge treatments produced superior switchgrass yields after three years. Both composting poultry manure and mixing paper mill sludge with fresh poultry layer manure can be used to effectively minimize phytotoxic mine soil conditions, minimize N leaching losses from poultry manure, and produce high switchgrass yields. Both of these treatments also generated larger stable N and C pools, implying greater sustainability of nutrient cycling. Furthermore, increased microbial activity and higher yields with fresh manure and paper mill sludge suggest increased benefits from direct application of these materials. This new approach could help alleviate the problems of both abandoned minelands and excess manure in Pennsylvania, while potentially generating revenue from switchgrass production.