FALL TILLAGE METHOD - EFFECT ON SHORT-TERM CARBON-DIOXIDE FLUX FROM SOIL

The increasing concern for rising CO2 concentrations from agricultural activities has prompted the need to better understand the flux of gre enhouse gases to the atmosphere. This work determines the effect of fo ur fall tillage methods on short-term CO2 flux from a Hemerly clay loa m (fine loamy, frigid Aeric Calciaquoll) in the northern Corn Pelt. Mo ldboard plow only, moldboard plow plus disk harrow twice, disk harrow once, and chisel plow once using standard tillage equipment following a wheat (Triticum aestivum L.) crop were compared with no-tillage. The CO2 flux was measured with a large portable system commonly used to m easure canopy gas exchange of field crops. Measurements of CO2 flux we re initiated within 5 min after tillage completion for each tillage tr eatment and continued intermittently for 19 d. Moldboard plow had the roughest soil surface and the highest initial CO2 flux (29 g m(-2) h(- 1)) and maintained the highest flux throughout the study. Moldboard pl ow plus disking twice and chisel plow had similar initial rates (7 and 6 g m(-2) h(-1), respectively) that were greater than disk harrow and no-tillage. The high initial CO2 fluxes were more related to depth of soil disturbance that resulted in a rougher surface and Larger voids than to residue incorporation. The differences in CO2 flux between til lage treatments were small but consistent 19 d after initial tillage a nd 64 mm rain. Lower CO, flux rates caused by tillage were associated with Low soil disturbance and/or small voids. Tillage methods affected the initial CO2 flux differently and suggest improved soil management can minimize agriculture's impact on global CO2 increase.