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 W; 0 and 112 kg N ha(-1) for barley (Hordeum distichon L.)]; and (iii) crop rotation Under NT soil management [corn-barley (NTCB); continuous corn (NT-CC); corn-dry bean (NI-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 nonsready 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(-1)d(-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 learn soil relative to CT plowed and fertilized soil.
