Soil carbon and nitrogen fractions after 19 years of farming systems research in the Coastal Plain of North Carolina

Authors: Franzluebbers, Alan; REBERG-HORTON, S - North Carolina State University; CREAMER, NANCY - North Carolina State University

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/25/2020
Publication Date: 4/1/2020
Citation: Franzluebbers, A.J., Reberg-Horton, S.C., Creamer, N.G. 2020. Soil carbon and nitrogen fractions after 19 years of farming systems research in the Coastal Plain of North Carolina. Soil Science Society of America Journal. https://doi.org/10.1002/saj2.20072.
DOI: https://doi.org/10.1002/saj2.20072

Interpretive Summary: Long-term agricultural experiments are an invaluable resource to better understand how management affects soil conditions, as well as how persistent soil, weather, and management conditions affect productivity, profitability, and environmental quality. A scientist from USDA-Agricultural Research Service in Raleigh, North Carolina collaborated with investigators at North Carolina State University to investigate the influence of 19 years of management on soil organic matter and soil biological activity. Conservation agriculture approaches using no tillage, grass-crop rotation, cover cropping, and organic amendments resulted in superior soil attributes for enhancing soil health conditions on a large field-scale experiment in Goldsboro NC. Managed timber and agricultural abandonment improved soil organic carbon near the soil surface, which allowed significant protection of the soil from erosion and offered opportunities for nutrient retention. However, innovative cropping systems that used rotation of pastures and crops over time and organically managed cropping systems stored more organic matter and allowed greater nutrient availability than other more conventional systems. This information will be valuable for farmers and extension agents to design robust and resilient agricultural management systems in the face of growing threats from climate change.

Technical Abstract: Long-term agricultural experiments in the Coastal Plain of the southeastern US are few, but needed to understand biogeochemical processes and help design better systems to overcome changing climate and other perturbations. We determined a suite of soil organic C and N fractions after 19 years of management from a diverse farming systems research project in Goldsboro, North Carolina. Soil was collected at 0-6, 6-12, 12-20, and 0-15 cm depth increments from 14 individual treatments that represented conventional cropping, integrated crop-livestock systems, organic cropping, plantation forestry, and old-field successional land use. Surface residue C and N were greater with woody (i.e. plantation forestry and successional) than with cropping systems (7491 and 2896 kg C/ha, respectively, and 138 and 60 kg N/ha, respectively). Soil-test biological activity was greater with alternative cropping (i.e. integrated crop-livestock and organic systems) (314 kg CO2-C/ha/3 d) than with conventional cropping (220 kg CO2-C/ha/3 d). An integrated crop-livestock system with grazed pasture in long rotation with crops had greater net N mineralization than hayed forage in shorter rotation (111 vs 92 kg/N ha/24 d, respectively). No-tillage cropping had greater total organic C and particulate organic N when sampled at single depth of 0-15 cm, but not when summed to 12 or 20 cm. We conclude that cropping systems with alternative management using forage-based rotations, limited tillage, and organic inputs can create long-lasting improvements in soil organic C and N fractions compared with more conventional agricultural systems.