Effect of Tillage and Nutrient Sources on Soil Organic Carbon Fluxes and Storage

Soils are a crucial component of global carbon cycling. The soil organic carbon pool is highly dynamic and strongly influenced by tillage and other management practices. Concerns over rapidly increasing atmospheric carbon dioxide levels have prompted considerable interest in soil carbon sequestration. However, the ability of conservation tillage systems to sequester carbon is still being debated. The objective of this field study was to quantify the effects of tillage and nutrient source on both fluxes and storage of soil organic carbon. The study site was located at the University of Wisconsin Agricultural Research Station near Lancaster, WI. Tillage plots at the site included chisel plow and no-tillage. These tillage treatments have been in operation since 1993; however, the study was conducted from 2003 to 2007. The nutrient sources were two types of manure (hog and beef manure) and a synthetic fertilizer (urea). Dissolved organic carbon losses in leachate and runoff were monitored year-around. Leachate samples were collected from a series of pan and wick lysimeters located at 0.6 and 1.2 m below the soil surface, while surface runoff from each plot was collected by isolating plots with galvanized sheet metal and collecting water in 1.7 m wide runoff collectors. In 2007, three soil cores to a depth of 120 cm were also taken from each plot to quantify soil carbon storage. In this presentation, we summarize the long-term effects of tillage as well as the short-term effect of manure addition on soil organic carbon dynamics.