Quantifying the Effects of Soil Salinity and Carbon Availability On Nitrous Oxide Emissions.

Application of organic amendments such as manures and composts improve soil physical, chemical and biological properties of salt-affected soils. However, organic amendments have greater potential for environmental pollution especially nitrous oxide (N₂O) because of their high N concentration. Soil salinity affects mineralization and nitrification processes of the N cycle. It might also affect production of N₂O and N₂O to N₂ ratio. We studied the effect of soil salinity and carbon availability from organic amendments on N₂O production and N₂O to N₂ ratio. Saline soils with EC_e of 3, 15 and 30 dS m^-1 were collected from Coachella Valley, California. Treatments included four organic amendments: a fresh green waste (FGW), green waste compost (GWC), fresh dairy manure (FDM) and dairy manure compost (DMC). All treatments were incorporated at a rate of 50 Mg ha^-1 and incubated in the laboratory at 25 °C for 90 days. Analysis of mineral N concentration periodically indicated that all treatments induced N immobilization in the first 7 days of incubation. However, N immobilization in both FGW and GWC continued up to 28 days of incubation, thereby reducing the availability of substrate for N₂O production during the first 28 days of the experiment. Additional data with respect to N₂O production will be presented.