|COLLINS, DOUGLAS - Washington State University|
|COGGER, CRAIG - Washington State University|
|FORGE, THOMAS - Agriculture And Agri-Food Canada|
|BARY, ANDREW - Washington State University|
|ROSSI, RICHARD - Newmont Mining Corporation|
Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/23/2010
Publication Date: 3/1/2011
Citation: Collins, D.P., Cogger, C.G., Kennedy, A.C., Forge, T., Collins, H.P., Bary, A.I., Rossi, R. 2011. Farm-scale variation of soil quality indices and association with edaphic properties. Soil Science Society of America Journal. 75:580–590. doi:10.2136/sssaj2010.0029.
Interpretive Summary: Soil life can be used as indicators of soil condition or soil quality because living soil organisms are often sensitive to changes in management. Soil physical and chemical properties and their variability can also affect soil organisms. In a study of organic farming management, increased soil aggregation was associated with more structured nematode communities. The time since tillage affected both decomposers and nematodes. Soils not tilled for 5 years had the largest microbial biomass and soils not tilled in the 2 weeks before sampling had the largest nematode populations. Comparisons of soil quality indicators across farms should be sensitive to indicators with soil texture and recent management practices. Methods of assessing soil chemical, physical, and biological soil quality indicators must be sensitive to changes in management practices, thus observing living soil organisms can assist scientists, organic growers and land managers in identifying best management practices to utilize in organic production systems.
Technical Abstract: Soil organisms are indicators of dynamic soil quality because their community structure and population density are sensitive to management changes. However, edaphic properties can also affect soil organisms and high spatial variability can confound their utility for soil evaluation. In the present study, we evaluate the relationship between two important agronomic functions, N-mineralization potential and aggregate stability, and biological, chemical and physical edaphic properties. Decomposer, nematode, and collembolan communities, C, N, pH, bulk density, and texture were evaluated at 81 sites across a 25-ha area of a working organic farm in Western Washington. We built regression trees with biological, chemical, physical, and management parameters to explain the farm-scale variation in microbial measurement, aggregates and nutrient cycling. Soils with microbial biomass >597 ug Cmic g-1 formed a homogeneous group with the greatest N-mineralization potential, and soils with >13.5% clay formed a homogeneous group with the greatest proportion of soil as aggregates. Increased soil aggregation was associated with more structured nematode communities, though much of the variability in SI remained unexplained by the data. The time since the last tillage event had a strong effect on both decomposer and total nematode populations. Soils not tilled for 5 years had the largest microbial biomass and soils not tilled in the 2 weeks before sampling had the largest nematode populations. Comparisons of soil quality indicators across farms should be sensitive to the association of indicators with soil texture and recent management practices.