Increasing atmospheric CO2 concentration has led to concerns about potential effects on production agriculture. In the fall of 1997, a study was initiated to compare the response of two crop management systems (conventional and conservation) to elevated CO2. The study used a split-plot design replicated three times with two management systems as main plots and two atmospheric CO2 levels (ambient and twice ambient) as split-plots using open top chambers on a Decatur silt loam (clayey, kaolinitic, thermic Rhodic Paleudults). The conventional 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 conservation 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. The effect of management and CO2 level on leaf level gas exchange during row crop (sorghum and soybean) reproductive growth over multiple growing seasons were evaluated. Treatment effects were fairly consistent across years. In general, higher photosynthetic rates were observed under CO2 enrichment (more so with soybean) regardless of residue management practice. Further, elevated CO2 led to decreases in stomatal conductance and transpiration, and water use efficiency was increased. No-till management also tended to increase seasonal photosynthetic rates, but the CO2 treatment effect was stronger. These 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.