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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 #317150
Title: Soil organic carbon and total nitrogen responses after 34 years of tillage of a sandy ultisol

Author
item Novak, Jeffrey
item Bauer, Philip
item HUNT, PATRICK - Retired ARS Employee
item Karlen, Douglas

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/14/2015
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Conservation tillage and crop management strategies are available to increase soil organic carbon (SOC) and total nitrogen (TN) contents, but long-term (> 30 yrs) field results quantifying these increases are sparse. Our objectives were to quantity above ground biomass inputs and changes in vertical (0 to 90 centimeters, (cm) distribution and accumulation (0 to 15 cm) of SOC and TN after growing row-, small grain, and cover crops for 34 years on a Norfolk loamy sand (Fine-loamy, kaolinitic, thermic, Typic Kandiudult) using either conservation or conventional tillage operations. The research site is located in the Coastal Plain region of South Carolina and was initiated in 1979, but this study focuses on results collected between 2002 and 2014. Composite soil samples were collected annually from 0 to 5, 5 to 10, and 10 to 15 cm depth increments, while bulk density samples were collected from shallow excavation pits. Subsoil samples (15 to 90 cm) were collected in 2002, 2008 and 2014. Overall, mean topsoil (0 to 15-cm) SOC and TN contents measured during the corn (Zea mays) and soybean (Glycine max) phases were significantly higher (8.23 versus 6.68 Mega-grams per hectare (Mg ha-1) for conservation versus conventional tillage treatments. Conservation tillage resulted in significant vertical stratification in SOC and TN in both topsoil and subsoil samples. There was a weak linear relationship between annual biomass inputs with both SOC and TN contents (r2 = 0.01 to 0.09; P > 0.05), but, mean SOC and TN concentrations were significantly correlated (r2 = 0.27 to 0.56; P < 0.08). This means that simply increasing topsoil SOC contents through conservation tillage translates to greater soil TN contents, and hence more nitrogen available for crop growth. Our results confirm that even on sandy Ultisols, 34 years of conservation tillage increased SOC and TN in the surface 15 cm by 4 and 2 Mega-grams per hectare, respectively, compared to conventional tillage practices, thus supporting its use to revitalize fertility and soil health of Southeast USA Coastal Plain soils.