Greenhouse Gas Implications of Restoration Using Organic Amendments.

Previous research has demonstrated that use of organic amendments is sufficient to restore ecosystem function in highly contaminated soils. Organic amendments have been used under a range of conditions to improve depleted soils by improving soil physical properties and total carbon concentrations. Recent sampling has shown that these amendments can also increase carbon storage for > 10 years after amendment addition across a wide range of land uses, soil types, and disturbances. Increases were also observed across a wide range of amendments including municipal solid waste composts, pulp sludges and municipal biosolids. This sampling also showed decreased bulk density and increased water holding capacity for many of the sites sampled. This suggests that terrestrial carbon sequestration can be accelerated through the use of organic amendments. Carbon accumulation appears to increase when amendments are incorporated into the soil rather than surface applied. One concern with this approach is the potential for nitrous oxide emissions in cases where high rates of organic amendments have been applied. Gas emissions from a borrow pit restored with different types of composts were higher for compost amended soils in comparison to fertilized soils. Emissions were somewhat decreased when composts were mixed with clean fill. These results suggest that organic amendments can accelerate recovery of degraded soils. There are likely management options that will increase benefits associated with use of amendments while simultaneously decreasing the likelihood of N2O release.