Effects of Residual Waste Material as Agricultural Soil Amendments on Soil Greenhouse Gas Fluxes

Abstract

Anthropogenic causes of rising levels of greenhouse gases (GHG) such as CO2, CH4, and N2O in the earth’s atmosphere are increasingly of concern due to their effects on climate change. Much of the earth’s carbon is retained in sinks created when atmospheric C is transformed into various forms of soil organic matter (SOM) and stored as stable, decay-resistant SOM for variable periods of time. When land is in its natural state, SOM is generally at a natural equilibrium of C inputs and outputs. Land use changes, particularly cultivation and conventional agricultural practices, have resulted in lower levels of SOM, leading to degraded, less productive soils. SOM is important to the physical, chemical and biological composition of the soil, and there has been a great deal of research addressing the impact of agricultural management practices on the retention of SOM and nutrients. One area of research is the use of organic waste materials as soil amendments to increase SOM. In addition to improving SOM, soil amendments also modify the physical, chemical, and biological properties of the soil, which affect the relative rates of production and consumption of GHG. The direct effects of the amendments are mediated by environmental factors that influence GHG flux, such as soil temperature and soil moisture. Organic wastes can be used as soil amendments either directly or after composting, providing an alternative to disposal in landfills or release into the environment as pollutants. The studies reported here examine the effects of residual waste materials (RWM) on GHG flux from agricultural soil. The amendments used included paper fiber with chicken manure (PF), dehydrated food waste (DFW), yard waste compost (YW), biosolids and yard waste compost (BIO), multisource compost (MC), and mineral fertilizer (MF). The first study measured GHG fluxes and assessed relationships between GHG fluxes and soil properties from a field, in Kingston, RI, sown in sweet corn during the 2014 growing season. During this study, DFW and PF produced significantly higher maximum CO2 fluxes than the control (CTL) (a field sown in buckwheat) in June. All other amended plots reached their maximum CO2 flux in August, but none where significantly different from the CTL. Measurements for CH4 and N2O did not follow a temporal pattern, and were not significantly different from the CTL. No soil properties were significantly correlated with the change in GHG flux from all soils, but CO2 and CH4 fluxes for CTL and MC,