Soil Organic Matter Mineralization after Compost Amendment

This is the authors' abstract. We don't add key points for this paper.

The addition of composts and manures to soils has often resulted in increased plant yields that are not obviously related to the nutrients in the added organic material. A study was conducted to determine if compost additions to soil resulted in increased mineralization of soil organic matter (SOM). The organic matter of a Sassafras sandy loam soil (fine‐loamy, siliceous, mesic Typic Hapludult) was labeled with 14 C by incubating uniformly labeled wheat ( Triticum aestivum L.) straw with the soil through a minimum of 60 wetting‐drying cycles during 2 yr. A municipal solid waste‐biosolids compost (MSWC) or a biosolids compost (BC) was added to the labeled soil or to acid‐washed sand and incubated for 1440 h. Decomposition of MSWC was low with 95% of the compost‐C remaining in sand or soil after 1440 h. Ninety‐two percent of BC‐C remained in sand and 86% remained in soil after 1440 h. Total and 14 CO 2 data indicated that neither compost stimulated SOM decomposition. Municipal solid waste‐biosolids compost reduced slightly SOM decomposition at 545 and 715 h. The soil, however, stimulated BC decomposition. Nitrogen mineralization of the BC + soil mixture was greater than soil alone, and the N apparently came from the compost. The benefits from addition of BC to Sassafras soil was not attributed to increased mineralization of SOM.