The optimum yield-scaled global warming potential (GWP) of perennial crops on arid land requires effective strategies for irrigation and fertilization. In 2009-2010, N 2O emissions and CH 4 oxidation were measured from an almond [ Prunus dulcis (Mill.) D.A. Webb] production system irrigated with nitrogen (N) fertilizers. Individual plots were selected within a randomized complete block design with fertilizer treatments of urea ammonium nitrate (UAN) and calcium ammonium nitrate (CAN). Event-related N 2O emissions from irrigation and fertilization were determined for seasonal periods of post-harvest, winter, spring and summer. Peak N 2O emissions in summer occurred within 24 h after fertilization, and were significantly greater from UAN compared to CAN ( p<0.001). Cumulative N 2O emissions from UAN were on average higher than CAN though not significantly different. Air temperature, water-filled pore space (WFPS), soil ammonium (NH 4+) and soil nitrate (NO 3-) showed significant positive correlation with N 2O emissions and significant negative correlation was found for the number of days after fertilization (DAF). The percentage of N 2O loss from N fertilizer inputs was 0.23% for CAN and 0.35% for UAN while CH 4 oxidation offset 6.0-9.3% of N 2O emissions. Total kernel yield was not significantly different between fertilizer treatments. Yield-scaled GWP for almond from CAN (60.9 kg CO 2eq Mg -1) and UAN (91.9 kg CO 2eq Mg -1) represent the first report of this metric for a perennial crop. These results outline effective irrigation and fertilization strategies to optimize yield-scaled GWP for almond on arid land.
