Increasing atmospheric CO 2 concentration could increase crop productivity and alter crop nutrient dynamics. This study was conducted (3 yrs) with two crops ([ Glycine max (L.) Merr.] and grain sorghum [ Sorghum bicolor (L.) Moench.]) grown under two CO 2 levels (ambient and twice ambient) using open top field chambers on a Blanton loamy sand under no-tillage. Macronutrient and micronutrient concentrations and contents were determined for grain, stover, and roots. Although elevated CO 2 tended to reduce nutrient concentrations, high CO 2 consistently increased nutrient content especially in grain tissue; this response pattern was more notable with macronutrients. The CO 2 effect was observed primarily in soybean. The consistent CO 2-induced increases in grain macronutrient contents favors reliable predictions of system outputs, however, predictions of crop nutrient inputs (i.e., stover and root contents) to the soil are less robust due to observed variability. Again, this is particularly true in regards to micronutrient dynamics in CO 2-enriched cropping systems.
