Nitrogen fertilization but not soil tillage affects nitrous oxide emissions from a clay loam soil under a maize-soybean rotation.

Pelster, D.E., Larouche, F., Rochette, P., Chantigny, M.H., Allaire, S.E., and Angers, D.A. (2011). "Nitrogen fertilization but not soil tillage affects nitrous oxide emissions from a clay loam soil under a maize-soybean rotation.", Soil & Tillage Research, 115-116, pp. 16-26. doi : 10.1016/j.still.2011.06.001  Access to full text

Abstract

Conversion of agricultural systems from conventional to no tillage practices usually increases soil carbon storage. However, adoption of no tillage may increase emissions of N2O, a very potent greenhouse gas. The objective of the study was to determine the effects of tillage (mouldboard plough [MP] and no-tillage [NT]) and three mineral N application rates (0, 80 and 160 kg N ha-1) on annual and biennial (2004–2005) N2O fluxes. The experiment was organized using a split-plot design using tillage as the main plots and fertilizer rates as the sub-plot. The site was an artificially drained and therefore well structured humic gleysol near Montreal QC, on a maize (Zea mays L.)–soybean (Glycine max L.) rotation. Emissions (April–November) ranged from 1.0 to 2.5 kg N2O–N ha-1. Throughout both years tillage had no effect (P > 0.05) on N2O emissions. During 2004, under maize cultivation, N2O emissions increased with the N fertilization rate (P < 0.001). Between 0.9 and 1.3% of applied fertilizer N was lost as N2O–N, similar to the IPCC estimate of 1%. There was also no significant interaction between tillage and N fertilization rate on N2O emissions during either year (P = 0.79). During the second year, under soybean cultivation, no N fertilizer was applied. As N2O emissions from the different fertilizer treatments were similar (P = 0.99), we concluded that there was no carry-over effect of the fertilization applied to maize in the previous year. Yield-based N2O emissions were similar between the different tillage types (P = 0.63 and 0.12 for 2004 and 2005, respectively) and fertilization rates (P = 0.30 and 0.84 for 2004 and 2005, respectively) and ranged from 17.0 to 22.7 g N2O–N kg-1 N export in 2004 and 6.6 to 12.8 g N2O–N kg-1 N export in 2005. Overall our results indicate that for this well-drained soil: (i) N fertilizer applications increased N2O emissions, supporting the use of IPCC-type emission factors; and (ii) soil tillage and the tillage–fertilization interaction had no measurable effect, consistent with previous reports that tillage of well-aerated agricultural soils has little effect on N2O emissions.