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Comparison of methods for measuring soil microbial activity using cotton strips and a respirometer

Nachimuthu, G.; King, K.; Kristiansen, P.; Lockwood, P. and Guppy, C. (2008) Comparison of methods for measuring soil microbial activity using cotton strips and a respirometer. Journal of Microbiological Methods, 69 (2), pp. 322-329.

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In order to develop a method of measuring the level of microbial activity in soil that is suitable for use by farmers, land managers, and other non-scientists, a simple method for determining soil microbial activity was evaluated and compared with two standard techniques. Soils sampled from vegetable farms in south east Queensland were incubated in the laboratory under controlled moisture and temperature conditions. Three methods were used to measure soil microbial activity, a respirometry method and two methods using the cotton strip assay (CSA) technique (image analysis and tensometer). The standard CSA method measured loss of tensile strength over a 35 day incubation period of buried cotton strips using a tensometer. The new CSA technique measured the intensity of staining by microbes using a flatbed scanner to create an image of the cotton strip whose staining percentage was determined using Photoshop® software. The respirometry method used the substrate induced respiration rate (SIR) to determine microbial biomass in the soil at day 12 of incubation. The strong correlation between the image analysis method and the tensometer method (r2 = 0.81), a technique used by scientific researchers, suggests that the image analysis method could be used to monitor aspects of soil biological health by general community land-care groups and farmers. The image analysis method uses equipment which is readily available and, while not strongly correlated with more precise measurements of soil biological activity such as microbial biomass (r2 = 0.26), it can detect gross trends in biological health in a soil monitoring program. The CSA method using image analysis was the cheapest technique to measure soil microbial activity. CSA using image analysis can be a valuable tool in conjunction with other simple indicators of soil physical and chemical health such as slaking and pH to monitor soil amelioration or rehabilitation programs.

EPrint Type:Journal paper
Keywords:microbial activity; microbial biomass; cotton strip assay; decomposition; soil biology; image analysis; substrate-induced respiration; tensile strength
Subjects: Soil > Soil quality > Soil biology
Knowledge management > Research methodology and philosophy
Research affiliation:Australia > University of New England
Deposited By: Kristiansen, Dr Paul Erik
ID Code:14040
Deposited On:28 Aug 2008
Last Modified:19 Jan 2012 08:41
Document Language:English
Refereed:Peer-reviewed and accepted
Additional Publishing Information:This work was an earlier trial for methods development for a PhD project assessing soil quality in organic vegetable farming. The soils tested were from organic and conventional farms.

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