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

Abstract

Particulate organic matter may be an important component feeding soil microbial activity. This study described population‐level statistics of particulate organic carbon (C) and nitrogen (N) in predominately 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−1 soil) varied from 2.0 to 18.0 (5% to 95% distribution) at 0‐ to 10‐cm depth, 0.4 to 3.9 at 10‐ to 30‐cm depth, and 0.1 to 1.9 at 30‐ to 60‐cm depth. As a proportion of total N, particulate organic N was 0.26 ± 0.10, 0.12 ± 0.09, and 0.08 ± 0.08 kg kg−1 at 0‐ to 10‐, 10‐ to 30‐, and 30‐ to 60‐cm depths, respectively. Particulate organic C was most dramatically affected at 0‐ to 10‐cm depth, following the order: conventional‐till cropland < no‐till cropland < grassland < woodland. Particulate organic N followed a similar order, except there was no difference between grassland and woodland. Particulate organic matter brings vitality to soil along a trajectory toward greater organic matter.