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ARS Home » Southeast Area » Florence, South Carolina » Coastal Plain Soil, Water and Plant Conservation Research » Research » Publications at this Location » Publication #383342
Research Project: Improvement of Soil Management Practices and Manure Treatment/Handling Systems of the Southern Coastal Plain

Location: Coastal Plain Soil, Water and Plant Conservation Research

Title: Contrasting carbon and nitrogen responses to tillage at different soil depths: An observation after 40-year of tillage management

Author
item PARAJULI, BINAYA - Clemson University
item YE, RONGZHONG - Clemson University
item LUO, MIN - Fuzhou University
item Ducey, Thomas
item PARK, DARA - Clemson University
item SMITH, MATTHEW - Clemson University
item Sigua, Gilbert

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/6/2021
Publication Date: 5/16/2021
Citation: Parajuli, B., Ye, R., Luo, M., Ducey, T.F., Park, D., Smith, M., Sigua, G.C. 2021. Contrasting carbon and nitrogen responses to tillage at different soil depths: An observation after 40-year of tillage management. Soil Science Society of America Journal. 85,4:1256-1268. https://doi.org/10.1002/saj2.20277.
DOI: https://doi.org/10.1002/saj2.20277

Interpretive Summary: The soils of the southeastern coastal plain are old and weathered. This results in soil with low carbon and nitrogen pools, as well as poor water retention, all of which negatively impacts soil fertility. To counteract these poor soil characteristics, soil management practices such as conservation tillage have been implemented to improve soil physical and chemical properties. In this study, we looked at the impact of forty years of conservation tillage on soil organic matter, which is comprised of carbon and nitrogen. We also examined microbial carbon and nitrogen cycling activities. These results were compared to conventional tillage - the standard tillage practice in the southeast United States. After forty years, we demonstrated significant increases in total carbon and nitrogen in the top two inches of soil under conservation tillage management, as well as increased microbial responses to carbon. Under conventional tillage, we demonstrated increased nitrogen concentrations 2 to 6 inches below the surface, as well as increased microbial responses to nitrogen. These results indicate a decoupling of carbon and nitrogen cycling in these soils, potentially driven by management practice. Such results may have long-term impacts on microbial community structure and function, and subsequently ecosystem services.

Technical Abstract: Conservation tillage (CS) is a major component of sustainable soil management. The objective of the study was to investigate the long-term impacts of CS on soil carbon (C) and nitrogen (N) pools and the associated microbial activities in sandy Ultisols. Soils (0-5 and 5-15 cm) were collected from fields under continuous CS and conventional tillage (CV) for 40 years and subjected to a range of physio-biogeochemical analyses. When compared with CV, CS increased total C, total N, and active C by 35%, 45%, and 44% at 0-5 cm, respectively, but not at 5-15 cm. In contrast, CV had 128% and 121% higher inorganic N and dissolved organic N at 5-15 cm depth, which was not observed at 0-5 cm. Respiratory CO2 production and organic N mineralization were found higher in CS soils than in CV soils at 0-5 cm, but both were higher in CV than CS at 5-15 cm. Concurrently with increased active C concentrations, potential activities of C-cycling enzymes were higher in CS soils than CV soils at 0-5 cm, which however were not observed at 5-15 cm. The increased labile C supply stimulated microbial activities in CS soils at 0-5 cm, but at 5-15 cm, the higher N availability increased microbial biomass N and organic N mineralization potentials in CV than CS soils. The contrasting CS and CV impacts on C and N at different soil depths likely reflected the decouple of C and N cycling in the tested soils.