Abstract: Nitrogen Transformation and Nitrous Oxide Emissions Affected By Biochar Amendment and Fertilizer Stabilizers. (ASA, CSSA and SSSA International Annual Meetings (2015))
369-3 Nitrogen Transformation and Nitrous Oxide Emissions Affected By Biochar Amendment and Fertilizer Stabilizers.
Suduan Gao, 9611 S Riverbend Ave., USDA-ARS, Parlier, CA and Zejiang Cai, USDA-ARS, Parlier, CA
Biochar as a soil amendment and the use of fertilizer stabilizers (N transformation inhibitors) have been shown to reduce N2O emissions, but the mechanisms or processes involved are not well understood. The objective of this research was to investigate N transformation processes and the relationship to N2O emissions from biochar amendment and use of the inhibitors. A sandy loam soil was collected from an orchard and incubated with 10% water content (field capacity ~17%) at 25oC and with application of either urea or urea and ammonium nitrate (UAN). Agrotain® Plus or Ultra (urease inhibitor) and N-Serve® 24 (nitrification inhibitor) were applied at recommended rates with fertilizer. Another potential N transformation inhibitor potassium thiosulfate (KTS) at 0.25-1:1 K2O/N ratio (w/w), and biochar at 1% (w/w) were also tested. Nitrogen transformation, N2O emission, and soil pH were monitored for five weeks. The Agrotain® products, N-Serve®, and biochar were all effective in reducing N2O emissions. Effective N2O emission reduction by KTS was only significant at a high ratio (1:1 K2O/N, w/w). Soil pH corresponded well to urea hydrolysis and nitrification processes. Biochar did not appear to affect either urea hydrolysis or nitrification, but resulted in significantly lower nitrite (NO2-, an intermediate product of nitrification) concentrations compared to no biochar amendment. The N2O emission was highly correlated with the NO2- concentration in soil. The inhibitors suppressed the N transformation processes, but their activities were limited to a few weeks after application. This research provides some information for better understanding of how biochar and fertilizer stabilizer can be utilized to mitigate N2O emissions and/or develop effective N management strategies.