PS 96-191 - Modeling N2O emissions for microirrigation systems in a nitrogen intensive perennial crop in California

Friday, August 12, 2011
Exhibit Hall 3, Austin Convention Center
M. Mar Alsina1, Ana Clara Fanton-Borges1, Kate M. Scow2, Patrick H. Brown3 and David R. Smart4, (1)Viticulture and Enology, University of California, Davis, CA, (2)Land, Air, and Water Resources, University of California-Davis, Davis, CA, (3)Department of Plant Sciences, University of California Davis, Davis, CA, (4)Viticulture and Enology, University of California Davis, Davis, CA

The atmospheric nitrous oxide (N2O) concentration has been growing at a constant rate since 1980. It reached a level of 319ppb in 2005, about 15% more than its pre-industrial concentration of approximately 278 ppb. Nitrogen fertilizers applied to soils and soil management are estimated to be the major sources of N2O production in agriculture. Approximately 30% of the total acreage of irrigated cropland in California is planted to orchards and vineyards and is irrigated and fertilized with nitrogen (N) using microirrigation systems (fertigation). Every type of water emitter generates a different water distribution in the wetted soil around it and when fertigating, the N will be distributed following the same pattern as water. Both soil water and N contents affect the generation of N2O and water content also affect the gas diffusion through the soil to the atmosphere. Our hypothesis was that two different microirrigation systems, drip and sprinkler, could result in different values of N2O-N emission at orchard level in almond, an intensively fertilized perennial crop. To achieve the objective we spatiotemporally sampled N2O emissions from the wet area around the emitter for conventional drip irrigation and for microsprinkler during 4 fertilization events along the year 2010.


Our results showed that spatial patterns of emission differed between the two irrigation systems leading to different values for the total mass of N2O-N emitted at orchard level. The total mass of N2O-N lost from the sprinkler irrigated orchard was 0.59 kg per ha while it was 1.48 kg per ha in the drip irrigated, during a year and with a total of 535 kg ha-1 of N applied in both treatments. Our results suggest that if the variability of N2O-N emission in the wetted area around the drip or sprinkler is not taken in account when calculating the N2O-N emitted from a micro irrigated orchard, the value might be overestimated in drip irrigation and underestimated in sprinkler irrigation.

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