Nitrous oxide emission at low temperatures from manure-amended soils under corn (Zea mays L.) Olga Singurindy 1 , Marina Molodovskaya, Brian K. Richards *, Tammo S. Steenhuis Department of Biological and Environmental Engineering, Riley-Robb Hall, Cornell University, Ithaca, NY 14853-5701, USA 1. Introduction A primary source of gaseous N losses to the atmosphere comes from the spreading of animal waste on agricultural fields, amounting to 35% of the global annual emission (Kroeze et al., 1999). Key agricultural management practices regulating N 2 O formation and release from agricultural fields include use of manure as a fertilizer, crop cultivation and land treatments. For a given amount of N applied to soils, manure application typically results in greater N 2 O emissions than does synthetic N fertilization (Clayton et al., 1997). Nitrous oxide is produced in soil by microbial nitrification and denitrification processes. The most important factors controlling these processes are soil mineral N (NH 4 + and NO 3  ) concentra- tions, oxygen partial pressure and, in the case of denitrification, available carbon to fuel the heterotrophic processes (e.g. Clough et al., 2003). Soil water content influences diffusion conditions in the soil and thus impacts the supply of oxygen (Robertson and Tiedje, 1987) which in turn controls the amount of N 2 O emitted. When the water filled pore space (WFPS) exceeds 60%, deni- trification becomes the dominant process producing N 2 O (e.g. Lemke et al., 1999), however production of N 2 O declines when the WFPS exceeds 80% because N 2 O is reduced to N 2 (Veldkamp et al., 1998). In contrast, any N 2 O production at WFPS below 60% is Agriculture, Ecosystems and Environment xxx (2009) xxx–xxx ARTICLE INFO Article history: Received 21 October 2008 Received in revised form 10 March 2009 Accepted 10 March 2009 Available online xxx Keywords: Nitrous oxide emission Denitrification Tillage effects Soil freeze–thaw Soil moisture content ABSTRACT Manure fertilization of soil significantly impacts the level of nitrous oxide (N 2 O) emission. Despite their short duration, periods of significant N 2 O emissions during soil thaws in winter and spring are an important portion of the total annual emissions from agricultural lands. The goal of this study was to understand the effects of tillage, moisture content and manure application on N 2 O emissions from agricultural soils at low temperatures. We summarize here both field and laboratory experiments. The field chamber study was focused on quantification of N 2 O flux from a field (Hudson clay loam: fine, illitic, mesic Glossaquic Hapludalf) growing corn (Zea mays L.) located in upstate New York. The field was moldboard plowed in the fall and then fertilized with liquid dairy manure. Intact soil cores were collected from the site both before and after field treatments for subsequent laboratory incubation that included freeze–thaw cycles. The results demonstrated that tillage reduced N 2 O emissions in non- manured soils by 20–30% in the 35–50 days following the tillage event, attributed to improved aeration resulting from reduced bulk densities and pore space saturation. The maximal emission of 200 mgNm 2 h 1 was found at soil temperatures greater than 5 8C and at WFPS between 40 and 70%. Subsequent application of liquid manure caused an increase in the total intensity of N 2 O emission. The emission of N 2 O from manure-amended soils was not limited to thawing events: emissions began at soil temperatures below 0 8C and continued even after complete soil freezing. The tillage history prior to manure application was found to have a significant influence on N 2 O emission during freezing/thawing cycles following manure application. The subsequent total winter N 2 O emissions were greater from the field areas that were tilled earlier in the fall, particularly in the first few freeze–thaw cycles, during which the maximum N 2 O fluxes occurred.Increasing soil saturation in a wet area formed during a spring thaw caused increasing N 2 O emissions up to a maximum of 200 mgNm 2 h 1 at 60–70% saturation. However, emissions dropped dramatically with further increases in soil moisture, decreasing to 50 mgNm 2 h 1 in the most saturated areas (90% saturated). Overall, maximal emissions were found at temperatures greater than 5 8C and at water filled porosities between 40 and 70%. ß 2009 Elsevier B.V. All rights reserved. * Corresponding author. Tel.: +1 607 255 2463. E-mail address: bkr2@cornell.edu (B.K. Richards). 1 Present address: Department of Earth and Ocean Sciences, University of British Columbia, BC, Canada. G Model AGEE-3390; No of Pages 8 Please cite this article in press as: Singurindy, O., et al., Nitrous oxide emission at low temperatures from manure-amended soils under corn (Zea mays L.). Agric. Ecosyst. Environ. (2009), doi:10.1016/j.agee.2009.03.001 Contents lists available at ScienceDirect Agriculture, Ecosystems and Environment journal homepage: www.elsevier.com/locate/agee 0167-8809/$ – see front matter ß 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.agee.2009.03.001