Greenhouse Gas Emissions From Irrigated Pecan Orchards of Arid New Mexico.

Nitrous Oxide is an important greenhouse gas; it is a precursor to ozone destroying NO and has a heating capacity 296 times that of CO₂. Biotic and anthropogenic activities have caused an increase in atmospheric N₂O with emissions from soils largely accounting for these increases. It has been shown that N₂O emissions correlate to moisture content fluctuations, however emissions from agricultural fields in the arid regions of the Southwest where rewetting events occur regularly are not well established. The objective of this study was to quantify N₂O emissions and present a conceptual analysis of the experimental results for irrigated Pecans for a semi-arid ecosystem of southern NM. The study began in September 2010 on a sandy loam soil and a silty clay loam soil, both under pecan trees (Carya illinoinensis). The small chamber technique was used to measure N₂O emissions from the soil surface between eight and ten in the morning, using four replicate chambers at each site. Soil samples were collected from each point during air sampling to determine soil moisture content and nitrate concentration. Soil cores were also collected at each point so that emissions could be measured from the cores at saturation, field capacity, and with a fertilizer application. Initial results showed that N₂O emissions were maintained near the baseline except for the few days following an irrigation event. Emissions from the sandy loam soil and a silty clay loam soil are shown to be below 3.2 and 1 μg N₂O-N m^-2 hr^-1 respectively, between irrigation events and 10.2 and 7.1 μg N₂O-N m^-2 hr^-1 respectively, during the few days following an irrigation event. From the initial results we concluded that emissions might be higher from agricultural fields subjected to intense rewetting events.