Evaluation of soil quality
Our ability to assess soil quality is complicated by many physical, chemical, and biological processes and their interactions in time, space, and intensity. It is not usually possible to directly measure the rate of soil processes; instead they can be inferred by measuring specific soil properties that are indicative of these rates. These measurements then can be used in simulation models to predict future changes in process rates and, in turn, soil quality. The properties measured are termed indicators of soil quality. The best soil quality indicators are those that integrate the combined effects of several properties and processes.
A general framework to evaluate soil quality is based on the following sequence: functions, processes, attributes (or properties) indicators, and methodology. Example of a framework (given in part) for evaluating soil quality; characterizing some of the capacities of a soil to perform a specific function (i.e., provide a medium for plant growth) is given in table below.
|Process||Attribute (or property)||Indicators||Possible method for determining attribute|
|Capacity to accept, hold, and release water||Infiltration||Infiltration rate, sorptivity||Tension permeameter|
|Water-holding capacity||Desorption curves||Tension table, pressure plate|
|Permeability||Hydraulic conductivity||Guelph permeameter|
|Capacity to accept, hold, and release energy||Organic matter||Organic C||Dry combustion|
|Labile organic matter||Microbial biomass||Chloroform fumigation|
|Particle size||Clay||Hydrometer / pipett|
(from: Carter et al. 1997)
Research efforts to monitor soil quality need to be balanced with efforts to better define relationships between the status of soil quality indicators and soil functions. In addition, consideration must be given to the simultaneity of diverse and sometimes conflicting nature of soil functions.
Acton, D.F., and Gregorich, L.J. 1995. The Health of Our Soils: Towards Sustainable Agriculture in Canada. Publication 1906/E. Available at: http://res2.agr.gc.ca/publications/hs/index_e.htm
Bowman, B. T. Soil quality versus soil health. Agriculture and Agri-Food Canada http://res2.agr.ca/london/faq/soil-sols_e.htm
Doran, J.W., and Jones, A.J. (eds.) 1996. Methods of assessing soil quality. SSSA Special Publication no. 49. Madison, WI.
Doran, J.W., and Parkin T.B. 1994. Defining and assessing soil quality. p. 3-21 In J.W. Doran et al. (ed.) Defining soil quality for sustainable environment. SSSA Spec. Publ. 35. SSSA, Madison, WI.
Doran, J.W., Sarrantonio, M., and Liebig, M.A. 1996. Soil health and sustainability. Advances in Agronomy 56:1-54.
Carter, M.R, Gregorich, E.G., Anderson, D.W., Doran, J.W., Janzen, H.H, and Pierce, F.J. 1997. Concepts of soil quality and their significance. In: Gregorich, E.G., and Carter, M.R. (eds.). Soil Quality for Crop Production and Ecosystem Health. Developments in Soil Science 25. Elsevier, New York. pp. 1-19.
Journal of Soil and Water Conservation. 1995. Volume 50 (May-June). Soil quality.
Karlen, D.L., Mausbach, M.J., Doran, J.W., Cline, R.G., Harris, R.F., and Schuman, G.E. 1997. Soil quality: a concept, definition, and framework for evaluation (a guest editorial). Soil Sci. Soc. Am. J. 61:4-10.
Larson, W.E., and Pierce, F.J. 1991. Conservation and enhancement of soil quality. In Evaluation of sustainable land management in the developing world. Vol. 2. IBSRAM Proc. 12(2). Bangkok, Thailand. Int. Board for Soil Res. and Management.
Letey, J. et al. 2003. Deficiencies in the soil quality concept and its application. J. Soil and Water Conserv. 58:180-187.
Norfleet, M.L, Ditzler, C.A, Puckett, W.E., Grossman, R.B., and Shaw, J.N. 2003. Soil quality and its relationship to pedology. Soil Sci. 168:149-155.
Soil Quality Institute. The Mission of the Soil Quality Institute (SQI) is to cooperate with partners in the development, acquisition and dissemination of soil quality information and technology to help people conserve and sustain natural resources and the environment. Web site http://soils.usda.gov/sqi
Sojka, R.E., and Upchurch, D.R. 1999. Reservations regarding the soil quality concept. Soil Sci. Soc. Am. J. 63:1039-1054.
USDA-NRCS Soil Quality Institute. 1999. Soil quality card design guide: a guide to develop locally adapted conservation tools. [statlab.iastate.edu/survey/SQI/]
Wang, C., BD. Walker, H.W. Rees, L.M. Kozak, M.C. Nolan, W. Michalyna, K.T. Webb, D.A. Holmstrom, D. King, E.A. Kenney, and E.F. Woodrow. 1994. Benchmark sites for monitoring agricultural soil quality in Canada. Soil Quality Evaluation Program Technical Report 1. (Former) Centre for Land and Biological Resources Research. Agriculture and Agri-Food Canada. [Available here]
Warkentin, B.P., and Fletcher, H.F. 1977. Soil quality for intensive agriculture. Pp. 594-598. Proceedings if the International Seminar on Soil Environment and Fertilizer Management in Intensive Agriculture. Society for Science of Soil and manure. National Institute of Agricultural Science, Tokyo, Japan.