Nitrogen, tillage, and crop rotation effects on carbon dioxide and methane fluxes from irrigated cropping systems
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.