Effect of Organic Amendments and Switchgrass Cultivation On Carbon Sequestration In Reclaimed Mine Soil.

Sequestration of C as stable soil organic matter is one mitigation strategy for steadily increasing atmospheric CO₂ concentrations.  Drastically disturbed soils, such as those at mine sites, typically have very low organic matter content, and thus have a potentially large capability to sequester carbon (C) during and following reclamation. Two separate experiments were initiated at mine sites in Pennsylvania in spring 2006 and spring 2009, utilizing reclamation treatments of lime and fertilizer, composted manure, or blends of fresh poultry manure and paper mill sludge (M+PMS) with adjusted C:N ratios of 20:1, under switchgrass (Panicum virgatum L.) cultivation. Results from these studies have indicated that mine soil amendment with composted manure or short fiber paper mill sludge (PMS) combined with manure effectively retained C in the soil. Post-reclamation C values ranged from 31.160 Mg C ha^-1 in lime and fertilizer treatments to 40 Mg C ha^-1 in compost and M+PMS treatments. The objective of this study is to distinguish between C increases due to amendments and biomass production, determine loss rate of amendment C, addition rate of biomass C, and to determine what fraction of soil C is truly stable and sequestered.  Soil samples were collected over periods of two and four years from both field sites and were analyzed based on water-stable aggregate size and distribution. Observed natural ¹³C abundance in both bulk soil and aggregate size fractions was utilized as a tracer for C additions during reclamation.  As higher biomass production resulted from application of M+PMS than from compost, lime or fertilizer applications, expected results are that soil C sequestration should also be higher in these treatments.