Interactive Effects of Wheel Traffic and Tillage System on Soil Carbon

The carbon-conserving nature of reduced or no-till soils as compared to conventionally tilled soils is well document­ ed (Blevins et al., 1983; Havlin et al., 1990; Wood and Edwards, 1992). With no-till, plant residues remaining on the soil surface decompose more slowly, resulting in more carbon (C) being retained in the soil than when residues are in­ corporated into the profile (Holland and Coleman, 1987). The negative effects of soil compaction on plant growth have been attributed primarily to a restriction of root growth. It has been suggested that soil compaction could affect the size and activity of the microbial biomass, and therefore, result in changes in cycling patterns of nutrients needed for plant growth (Griffin, 1978; Dick et al., 1988). Soil compaction may affect microbial biomass dynamics via changes in available pore space (Dick et al., 1988). These microbial shifts lead to changes in rates of decomposition and mineralization of nutrients into plant available forms. However, there remains a lack of research investigating the biological effects of soil compaction and its interaction with tillage systems. The purpose of this study was to determine seasonal changes occurring in the cycling of C caused by to tillage and compaction.