Soil carbon and nitrogen mineralization after the initial flush of CO2

Authors: Franzluebbers, Alan

Submitted to: Agricultural and Environmental Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/27/2019
Publication Date: 2/19/2020
Citation: Franzluebbers, A.J. 2020. Soil carbon and nitrogen mineralization after the initial flush of CO2. Agricultural and Environmental Letters. https://doi.org/10.1002/ael2.20006.
DOI: https://doi.org/10.1002/ael2.20006

Interpretive Summary: Management to achieve healthy, functioning soil is needed to meet production and environmental goals of sustainable agricultural systems. Soil biological activity and its role in nitrogen mineralization are key components of soil health evaluation. A scientist from USDA-Agricultural Research Service conducted an in-depth study to evaluate how short- and longer-term carbon and nitrogen mineralization were associated in five soils from Georgia and North Carolina. Mathematical descriptions of carbon mineralization were consistent and logical, but similar descriptions for nitrogen mineralization were more complicated. However, associations between soil-test biological activity and long-term nitrogen mineralization were logical and consistent. In conclusion, soil-test biological activity offers a simple, rapid, and robust indication of soil nitrogen mineralization. Greater utilization of the tool will inform land managers of the important role that biologically active organic matter plays in nutrient cycling. This understanding is greatly needed so that (a) agricultural systems can become more efficient in nitrogen utilization and (b) agricultural advisers can help growers remain profitable and avoid unnecessary losses of nitrogen to the environment.

Technical Abstract: Soil health evaluation with biological activity requires standardization for greater understanding across environments. Soil-test biological activity can be measured with the flush of CO2 during the first 3 d following rewetting of dried soil, but how this indicator relates to long-term soil N mineralization has been lacking. This study evaluated short- and longer-term C and N mineralization in five soils from Georgia and North Carolina to validate associations between soil-test biological activity and net N mineralization. Although mathematical descriptions of cumulative C mineralization were logical and consistent in structure, descriptions of net N mineralization were complicated by the need to fit to different model types. Taking the focus away from mathematical description and putting emphasis on associations between linked processes of C and N mineralization resulted in simple, logical, and relatable interpretations. Soil-test biological activity is a simple, rapid, and robust indicator of soil N availability.