| Soil compaction is a major cause of reduced crop productivity in agroecosystems and increases the potential for environmental problems. Compaction-induced changes in soil physical properties may modify soil microhabitats and affect soil microbially mediated processes related to nutrient cycling. Laboratory and field experiments were conducted to determine the effects of compaction, poultry-litter application and cropping on soil physical and microbiological properties related to carbon (C) and nitrogen (N) in claypan soils. Compaction significantly increased soil bulk density, decreased saturated hydraulic conductivity and total porosity, and shifted macropores to micropores. These compaction-induced physical changes decreased soil CO2 efflux and changes in total inorganic N. Total organic C, beta-glucosidase and beta-glucosaminidase activities, microbial biomass C (MBC) and microbial functional diversity of soil were increased due to moderate compaction (i.e., bulk density levels of 1.2 to 1.6 Mg m-3) and were not affected or decreased under more severely compacted conditions (1.8 Mg m-3). Decreased soil N fractions, including soil microbial biomass N and soluble organic N, after compaction suggest that these variables were more sensitive to soil compaction than soil C fractions. Compaction increased the soil microbial C:N ratio, which may suggest a structural shift of soil microbial community to fungi. Litter application and cropping increased most measured soil microbiological properties, except microbial C:N ratio. These results suggest that soil compaction changes these soil microbiological properties, and the magnitude of those changes is modified by climatic variation. Use of organic amendments and cropping may mitigate the compaction effects on these soil microbiological properties over time. |
