Soil Nitrogen Dynamics and Miscanthus Yield of an Amended, Reclaimed Mine Soil.

Abandoned surface mines, of which there are more than 76,500 hectares in Pennsylvania, are generally low in organic matter and nutrients for plant growth. The mushroom industry in Pennsylvania annually produces approximately 535,000 m³ of spent mushroom substrate (SMS), which is high in organic matter and plant nutrients. Our objective was to evaluate the potential of SMS to improve production of Miscanthus x giganteus (Giant Miscanthus) on abandoned mine lands. Amendments were surface applied at four rates of SMS (13.45, 26.9, 40.35, 53.8 Mg ha^-1 'as-is') , and four rates of an inorganic fertilizer blend (urea, triple superphosphate, and muriate of potash) to provide equivalent amounts of nitrogen, phosphorus, and potassium. In situ incubation was used over 7 sampling intervals from mid-May until late November to estimate the cumulative potentially mineralizable-N to represent soil nitrogen availability. Plots were harvested in late November and sampled to estimate dry matter (kg ha^-1) and nitrogen removal (kg ha^-1). Results indicate that increasing nutrient application produces significant differences in cumulative potentially mineralizable-N, dry matter yield, and nitrogen removal. However, amendment sources did not differ in these parameters.  Overall, dry matter yield increased with increased addition of nitrogen, phosphorus, and potassium. However, 40.35 Mg SMS ha^-1 produced yields comparable to 53.8 Mg SMS ha^-1 and the highest fertilizer rate. This could indicate that nutrient addition equal to or greater than 40.35 Mg SMS ha^-1 does not produce significant yield response. However, the comparable fertilizer application to 40.35 Mg SMS ha^-1 should have produced a similar yield if this were true. Also, there appear to be no differences in soil nitrogen availability between amendment sources. This may indicate that a non-nutrient factor such as pH buffering, water-holding capacity, weed control, etc. due to amendment source may explain differences in yield.