ArticleTHE EFFECTS OF COMPOST AND CROP ROTATIONS ON CARBON TURNOVER AND THE PARTICULATE ORGANIC MATTER FRACTIONFortuna, A.1; Harwood, R. R.2; Paul, E. A.3Author Information 1USDA-Agricultural Research Service, New England Plant, Soil, & Water Laboratory, University of Maine, Orono, ME 04469–5753. 2Dept. of Crop and Soil Sciences, Plant and Soil Sciences Bldg., Michigan State University, East Lansing, MI 48824. 3Natural Resources Ecology Lab, NESB, Colorado State University, Fort Collins, CO, 80523. Dr. Fortuna is corresponding author. E-mail: [email protected] Received June 21, 2002; accepted Feb. 24, 2003. Soil Science: June 2003 - Volume 168 - Issue 6 - p 434-444 doi: 10.1097/01.ss.0000075288.53382.91 Buy Metrics Abstract Management practices that influence the quantity of C inputs returned to the soil from cropping systems and compost applications alter subsequent biotic activity broadly, contribute to seasonal fluctuations in nutrient dynamics, and may increase C sequestration. The effects of crop rotations and compost applications on soil-C sequestration and decompostion, and the turnover time of C4-derived corn C were assessed via changes in the C content and 13C values of particulate organic matter (POM) and total soil organic C (SOC). The majority of organic inputs entered the POM fraction, defined as the sand-sized soil separates remaining on a 53-μm sieve after removal of residues (>2 mm), dispersion in 5% sodium polyphosphate, and 12 h of shaking. Before the application of compost to soil, 85% of the C in the compost material was classified as POM. Measurements of POM-C in the soil were 45% higher and SOC was 16% greater where compost was applied in place of N fertilizer. Addition of compost to POM-C diminished the value of POM as an indicator of short-term changes in nutrient dynamics. However, POM-C remaining from compost applications made during the period 1993 to 1997 may be an indicator of enhanced macroaggregate stability: improved soil tilth and the retention of soil C and N. The turnover time of C4-derived C in the POM fraction was 11 years compared with 22 years in SOC. The presence of compost C did not affect the turnover time of corn-derived C. High cropping intensity and chisel plow management increased C sequestration relative to the preceding alfalfa management. © 2003 Lippincott Williams & Wilkins, Inc.