Effects of Atmospheric CO₂ Enrichment on Crop Nutrient Dynamics under No-Till Conditions

ABSTRACT

Increasing atmospheric CO₂ 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 CO₂ 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 CO₂ tended to reduce nutrient concentrations, high CO₂ consistently increased nutrient content especially in grain tissue; this response pattern was more notable with macronutrients. The CO₂ effect was observed primarily in soybean. The consistent CO₂-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 CO₂-enriched cropping systems.

Keywords:

• elevated CO₂
• conservation tillage
• soybean
• sorghum
• macronutrients
• micronutrients

ACKNOWLEDGMENTS

The authors thank B.G. Dorman and S.A. Morey for technical assistance. This research was supported by the Biological and Environmental Research Program (BER), U.S. Department of Energy, Interagency Agreement No. DE-AI02-95ER62088.

Notes

∗ Significance levels from the mixed models procedure of SAS.

∗ Significance levels from the mixed models procedure of SAS.

∗ Significance levels from the mixed models procedure of SAS.

∗ Significance levels from the mixed models procedure of SAS.

∗ Significance levels from the mixed models procedure of SAS.