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TECHNICAL REPORTS

Nitrogen, Tillage, and Crop Rotation Effects on Carbon Dioxide and Methane Fluxes from Irrigated Cropping Systems

^a Dep of Agronomy, Forest and Land Management, Univ. of Turin, via L. da Vinci 44, 10095 Grugliasco (TO), Italy
^b USDA–ARS, 2150 Centre Ave., Bldg. D, Suite 100, Fort Collins, CO 80526-8119. Contribution from USDA-ARS, Fort Collins, CO. The U.S. Department of Agriculture offers its programs to all eligible persons regardless of race, color, age, sex, or national origin, and is an equal opportunity employer. Mention of trade names or proprietary products does not indicate endorsement by USDA and does not imply its approval to the exclusion of other products that may be suitable

^* Corresponding author (ardell.halvorson{at}ars.usda.gov).

Received for publication December 15, 2008. Long-term effects of tillage intensity, N fertilization, and crop rotation on carbon dioxide (CO₂) and methane (CH₄) flux from semiarid irrigated soils are poorly understood. We evaluated effects of: (i) tillage intensity [no-till (NT) and conventional moldboard plow tillage (CT)] in a continuous corn rotation; (ii) N fertilization levels [0–246 kg N ha^–1 for corn (Zea mays L.); 0 and 56 kg N ha^–1 for dry bean (Phaseolus vulgaris L.); 0 and 112 kg N ha^–1 for barley (Hordeum distichon L.)]; and (iii) crop rotation under NT soil management [corn-barley (NT-CB); continuous corn (NT-CC); corn-dry bean (NT-CDb)] on CO₂ and CH₄ flux from a clay loam soil. Carbon dioxide and CH₄ fluxes were monitored one to three times per week using vented nonsteady state closed chambers. No-till reduced (14%) growing season (154 d) cumulative CO₂ emissions relative to CT (NT: 2.08 Mg CO₂–C ha^–1; CT: 2.41 Mg CO₂–C ha^–1), while N fertilization had no effect. Significantly lower (18%) growing season CO₂ fluxes were found in NT-CDb than NT-CC and NT-CB (11.4, 13.2 and 13.9 kg CO₂–C ha^–1d^–1 respectively). Growing season CH₄ emissions were higher in NT (20.2 g CH₄ ha^–1) than in CT (1.2 g CH₄ ha^–1). Nitrogen fertilization and cropping rotation did not affect CH₄ flux. Implementation of NT for 7 yr with no N fertilization was not adequate for restoring the CH₄ oxidation capacity of this clay loam soil relative to CT plowed and fertilized soil.

Abbreviations: CT, conventional moldboard plow tillage • CT-CC, conventional-till continuous corn • DOY, day of year • GHG, greenhouse gas • LSD, least significant difference • MDF, minimum detectable flux • NT, no-till • NT-CB, no-till corn-barley • NT-CC, no-till continuous corn • NT-CDb, no-till corn-dry bean • SOC, soil organic C • SOM, soil organic matter • UAN, urea ammonium nitrate fertilizer • WFPS, water-filled pore space • _b, soil bulk density