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

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.