Spatiotemporal variation of event related N2O and CH4 emissions during fertigation in a California almond orchard. Issue 1 (10th January 2013)

• Record Type: Journal Article
• Authors: Alsina, Maria Mar; Fanton-Borges, Ana Clara; Smart, David R.
• Is Part Of: Ecosphere. Volume 4:Issue 1(2013)
• Page Start: 1
• Page End: 21
• Publication Date: 2013-01-10
• Subjects: almond orchard -- California, USA -- emission -- fertigation -- GHG -- microirrigation systems -- trace gas -- woody perennials; Ecology -- Periodicals; Ecology; Periodicals; 577.05
• DOI: 10.1890/ES12-00236.1
• Languages: English
• ISSNs: 2150-8925

Abstract

Abstract : Nitrogen fertilizer applied to soil is the primary source of the greenhouse gas (GHG) nitrous oxide (N2 O). The assessment of N2 O emissions, or net fluxes of the GHG methane (CH4 ), are lacking for upland, arid agricultural ecosystems worldwide. In California, where rates of application for nitrogen (N) can exceed 300 kg per hectare for N‐intensive fruit and nut crops (>2 million acres), liquid N fertilizers applied through microirrigation systems (fertigation) represent the predominant method of N fertilization. Little information is available for how these concentrated and spatially discrete N solution applications influence N2 O emissions and net CH4 fluxes (the sum of methanogenic and methanotrophic activity). In this study we examined soil N2 O‐N emissions and net CH4 fluxes for drip and stationary microsprinklers, two of the most widely used fertigation emitters, in an almond orchard where 235.5 kg N/ha were applied during the season of measurement (2009–2010). We accomplished this by modeling the spatial patterns of N2 O and CH4 at the scale of meters and centimeters using simple mathematical approaches. For two applications of 33.6 kg/ha and three applications of 56.1 kg/ha targeted to the phenologic stages with highest tree N demand, the spatial patterns of N2 O fluxes were similar to the emitter water distribution pattern and independent of temperature and fertilizer N form applied. Net CH4 fluxes were extremely low and there was no discernible spatial pattern, but areas kept dry (driveways between tree rows) generally consumed CH4 while it was produced in the microirrigation wet‐up area. The N2 O‐N emissions for fertigation events at the scale of days, and over a season, were significantly higher from the drip irrigated orchard (1.6 ± 0.7 kg N2 O‐N ha −1 yr −1 ) than a microsprinkler irrigated orchard (0.6 ± 0.3 kg N2 O‐N ha −1 yr −1 ). N2 O emissions and net CH4 fluxes were only significantly correlated with soil water filled pore space and not with mineral‐N. The correlation was much better for N2 O emissions. Our results greatly improve our ability to scale N2 O production to the orchard level, and provide growers with a tool for lowering almond orchard carbon and nitrogen footprints.