Soil carbon dioxide efflux from a claypan soil affected by surface compaction and applications of poultry litter

The effects of soil compaction on soil physical properties may alter soil microbial activities and processes, including carbon (C) cycling, and possibly affect agricultural production and environmental degradation. This study investigated the effects of surface soil compaction on soil C mineralization in a claypan soil amended with poultry litter (i.e. turkey excrement mixed with pine shavings as bedding). In a laboratory study, a Mexico silt loam soil was compacted to four bulk density levels (1.2, 1.4, 1.6 and 1.8 Mg m(-3)) with and without poultry litter and incubated at 25 C for 42 days. A field experiment with plots that were maintained fallow was also conducted in 2001 and 2002 on the same claypan soil in North Central Missouri. Soil was amended with litter (0 and 19 Mg ha(-1)) and left uncompacted or uniformly compacted. Results showed that soil CO2 efflux was decreased by compaction up to 72% in the laboratory study and 46% in the field study of 2002 (P < 0.05). Litter application enhanced soil CO2 efflux (P < 0.05) due to the addition of readily available C from litter. In the laboratory study, soil CO2 efflux was negatively correlated with soil bulk density and the proportion of micropores (P < 0.05). Conversely, soil CO2 efflux was positively related with total porosity and the proportion of macropores (P < 0.05). In the field, surface soil compaction caused changes in soil water content and soil aeration, which may have had the greatest effect on variation in soil CO2 efflux. These results indicate that both soil compaction and litter application change the rate of soil C mineralization, and the magnitude of those changes is modified by climatic variation. (c) 2005 Elsevier B.V. All rights reserved.