Saturday, 15 July 2006

Nutrient Leaching from Coal Refuse Amended with Reclamation Rates of Composted or Fresh Poultry Layer Manure.

Richard Stehouwer, Pennsylvania State Univ, 116 ASI Building, University Park, PA 16801

In several US Mid-Atlantic states concentrated animal agriculture has led to regional excess manure and nutrient concentrations in close proximity to coal mining regions where organic C and nutrients are needed for reclamation. However, the quantity of manure required for revegetation of phytotoxic mine spoil could result in significant nutrient leaching. Prior composting of manure or co-application with high organic C materials are two possible means to limit nutrient loss. We investigated the potential nutrient leaching in a greenhouse experiment in which columns of coal mine spoil were amended with 3 rates of composted layer manure (total N from 0.4 1.1 g N kg-1 refuse) or fresh layer manure (total N 0.4 g N kg-1 refuse) combined with paper mill sludge to achieve amendment C/N ratios ranging from 7 to 40. Columns were planted with switchgrass (Panicum virgatum) and intentionally leached every four weeks. All amendments increased switchgrass growth over unamended refuse and refuse amended with limestone and inorganic fertilizer. Growth increased with increased compost addition, but increased much more with paper mill sludge addition. Nitrate leaching was not increased by compost addition (total leaching losses < 2 mg NO3-N column-1) but was very large with fresh layer manure at C/N ratios of 7 and 20 (total leaching losses of 191 and 113 mg NO3-N column-1 respectively). With C/N ratios of 30 and 40 leachate NO3 was substantially reduced (total leaching losses of 23 and 48 mg NO3-N column-1 respectively). Amendment effects on NH4 leaching were very similar NO3 leaching, thus total N losses were nearly two times larger than NO3 leaching losses. Total P leaching losses were greatest with fresh manure at C/N ratio of 7, but all additions of paper mill sludge reduced P loss to <2 mg P column-1. P losses were similarly reduced by composting the manure. Both composting and C/N ratio adjustment reduce potential nutrient loss from reclamation uses of poultry manure. Co-application of manure and a high C material may be economically preferable because it avoids the additional material handling and time costs of composting.

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