_GENERAL DOCUMENTS - C1981017 (250)

Home Browse Search

material is being utilized as an organic amendment to improve the chemical and physical characteristics of the plant growth medium, rather than solely as a surface cover mulch. Concerns were expressed with regard to the material tending to bind available nitrogen. Temporary immobilization of soil nitrogen can occur when nitrogen poor mulch or other plant residue with high carbon to nitrogen (C:N) ratio is added, because available nitrogen may be tied up by microbes as they break down the organic material. This concern is addressed by several components of the reclamation plan. First, the specification is for native grass hay, which is significantly higher in protein, and total nitrogen content than wheat straw, which is commonly used as mulch. The C:N ratio for grass hay would be less than half the ratio for wheat straw. Second, the specification calls for the addition of approximately 50# per acre of nitrogen fertilizer, which should offset any temporary immobilization of soil nitrogen. Third, the fact that revegetation will occur in the fall is of significance. Martin Alexander, in Introduction to Soil Microbiology, states that immobilization accompanying soil amendment with nitrogen poor crop residues may actually be beneficial in the autumn, because nitrate and ammonium are tied up and are not lost by leaching during the winter season. The following growing season, nitrogen bound up in microbial tissue is mineralized in part to forms that can be utilized by plants. It is important to note that this practice was utilized previously by AML at a pre-law mine disturbance in Coal Basin, with site conditions very similar to those existing at Mines 3 and 4. It is my understanding that a successful stand of seeded vegetation was established, and that no indications of nitrogen deficiency were observed. An additional concern expressed by Savage and Savage with respect to the high mulch application rate was that the mulch could inhibit plant growth through moisture deprivation and light recuction to seedling plants. These problems could possibly occur if the mulch were spread in a blanket several inches thick, completely covering the soil surface. However, this will not be the case since the mullch will be thoroghly incorporated into the soil as an amendment. The potential for moisture deprivation at these sites is lower than at any other coal operation in the state. Winter snowpack accumulates many feet deep on these relatively flat, east exposures, with soil profiles saturated when spring snowmelt occurs. During the summer, afternoon thunder showers are common, and annual precipitation exceeds 20 inches. Please let me know if I can be of further assistance. cc: Larry Routten Jim McArdle c:\cbaseed.dtm