N2O and CO2 Emissions From Mined Land Reclaimed Using Organic Amendments.

N₂O and CO₂ Emissions from Mined land Reclaimed Using Organic Amendments

Abstract

Organic amendments such as biosolids, manure, compost and industrial by-products can be effective in restoring soil productivity to degraded soils of surface mine sites due in part to the large amounts of N and organic C they provide. These additions could also result in soil conditions that favor nitrous oxide (N₂O) and carbon dioxide (CO₂) emissions but there has been little investigation of this potential. We conducted an in situ experiment to compare N₂O and CO₂ fluxes with the following 7 soil amendment treatments: poultry layer manure, composted poultry manure, poultry layer manure mixed with three rates of paper mill sludge (PMS) (C: N ratios of 14:1, 21:1 and 28:1), one lime and inorganic fertilizer and a non-amended control. The experiment was carried out at ambient and increased soil moisture conditions in field plots at an active coal mine site situated in Clearfield County, PA. Gas and soil samples were collected on 0, 1, 3, 7, 15, 22, 31, 57 and 90 days after the treatments were applied. Gas samples were analysed for N₂O and CO₂ by gas chromatography and soil samples were extracted with KCl and analysed for NH₄ ⁺ and NO₃^- using colorimetric methods. All organic treatments increased N₂O and CO₂ emissions relative to the control and lime + fertilizer treatments. The largest increases occurred with the manure and PMS treatment with C:N ratio 21:1 both in dry and moist condition on one sampling date which was the 31^st day of application of amendments. This could be due to enhanced microbial activity increasing the availability of C and N in soil after amendment applications which needs to be examined further. Except on the 31^st day of application, the emissions were low in all organic treatments in both dry and moist condition indicating that they can be used for reclamation purposes.