Technical Abstract: Increasing atmospheric CO2 concentration may impact production agriculture. In the fall of 1997, a study was initiated to examine the response of different tillage systems to changing atmospheric CO2 level. The study used a split-plot design (three replications) with two tillage systems (conventional tillage and no-tillage) as main plots and two atmospheric CO2 levels (ambient and twice ambient) as sub-plots using open top chambers on a Decatur silt loam (clayey, kaolinitic, thermic Rhodic Paleudults). The conventional tillage system was a grain sorghum [Sorghum bicolor (L.) Moench.] and soybean [Glycine max (L.) Merr.] rotation with winter fallow and spring tillage practices. In the no-tillage system, sorghum and soybean were rotated and three cover crops were used [crimson clover (Trifolium incarnatum L.), sunn hemp (Crotalaria juncea L.), and wheat (Triticum aestivum L.)] under no-tillage practices. Over multiple growing seasons (three for each crop), the effect of management and CO2 level on leaf level gas exchange during row crop reproductive growth were evaluated. Findings were fairly consistent across years with higher photosynthetic rates being observed under high CO2 (more so with soybean) regardless of management practice. Further, elevated CO2 led to decreased stomatal conductance and transpiration, and increased water use efficiency. Results suggest that better soil moisture conservation and high rates of photosynthesis can occur in both tillage systems in CO2-enriched environments during reproductive growth.