Soil depth distribution of particulate organic carbon and nitrogen in the southeastern USA

Authors: Franzluebbers, Alan

Submitted to: Agricultural & Environmental Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/7/2024
Publication Date: 11/27/2024
Citation: Franzluebbers, A.J. 2024. Soil depth distribution of particulate organic carbon and nitrogen in the southeastern USA. Agricultural & Environmental Letters. Vol 9, Issue 2. https://doi.org/10.1002/ael2.70005.
DOI: https://doi.org/10.1002/ael2.70005

Interpretive Summary: Organic matter takes on different forms in soil. One of these forms is particulate organic matter. This fraction is physically isolated as particles the size of sand grains, that is greater than 0.053 mm. An ARS scientist in Raleigh North Carolina summarized the concentrations of particulate organic carbon and nitrogen from a diversity of soils under four broad land-use categories collected in Georgia, South Carolina, North Carolina, and Virginia. These land uses were conventional-till cropland, no-till cropland, grassland, and woodland. Particulate organic carbon and nitrogen concentrations were greatest near the soil surface and declined exponentially with depth in the soil profile. In the surface 4 inches of soil, particulate organic matter matched the conservation gradient. Low values were observed under land uses with least conservation management (tilled soil and no cover crops) and high values were observed under land uses with permanent cover and little to no soil disturbance. These results will provide a valuable set of standards in the southeastern USA to which other data can be compared regarding impact of land use on soil organic matter.

Technical Abstract: Particulate organic matter may be an important component feeding soil microbial activity. This study described population-level statistics of particulate organic C and N in Ultisols across 181 farms throughout North Carolina, Virginia, and Georgia. Soil profiles were sampled under conventional-till cropland (n=186), no-till cropland (n=127), grassland (n=322), and woodland (n=171). Particulate organic C (g C/kg soil) varied from 2.0 to 18.0 (5 to 95% distribution) at 0-10-cm depth, 0.4 to 3.9 at 10-30-cm depth, and 0.1 to 1.9 at 30-60-cm depth. As a proportion of total N, particulate organic N was 0.26, 0.12, and 0.08 kg/kg at 0-10-, 10-30-, and 30-60-cm depths, respectively. Particulate organic C and N were most dramatically affected at 0-10-cm depth, following the order: conventional-till cropland < no-till cropland < grassland