Switchgrass production on abandoned mined land reclaimed with manure based amendments

Reclaimed mined lands are an underutilized resource that could produce biomass for biofuels. Due to low quality soils on mined lands, biomass yields are likely to be below those of agricultural soils. To determine if manure based soil amendments could be used to rapidly increase soil organic C and nutrient pools and their effect on biomass yields, we conducted an experiment on an acidic abandoned mined land soil in which switchgrass was planted following soil amendment with composted poultry layer manure (67 and 134 Mg ha^-1, 30 and 60), layer manure mixed with paper mill sludge (PMS) (manure N equivalent to 67 Mg ha^-1 compost, mixed at C:N ratios of 20 and 30), or with lime and inorganic fertilizer. The experiment was established in 2006 and soil pH, total C and N, switchgrass yield, and tissue N, P and K were measured. By 2009 soil organic C in the upper 5 cm of soil increased from 3.2% before reclamation to 5.9 to 6.9% with manure based amendments, and to 4.2% with lime and fertilizer amendment. Soil N in the upper 5 cm was 0.09% before reclamation and in 2009 had doubled with lime and fertilizer, tripled with manure+PMS, and quadrupled with compost amendments. In each year of switchgrass production the manure based amendments produced more biomass than the lime and fertilizer amendments. In 2009 yields ranged from 4 to 5 Mg ha^-1 (1.8 to 2.2 ton acre^-1)for the manure based amendments, and just over 2 Mg ha ^-1 (0.9 ton acre^-1) for lime and fertilizer amendment. Harvest removal of N suggests yields may not be sustainable without periodic addition of N. These results show that amendment with manure based materials can improve mine soil quality and nutrient supply to substantially increase switchgrass yield potential.