NSCP Research - Project J
Soil Biota as Indicators of Soil Quality
Several components in the Soil Quality Evaluation Project (SQEP) under NSCP as well as field staff such as the Soil Conservation Advisors are involved in predicting changes in soil characteristics. These characteristics may be described as those which are useful for identifying soil quality degradation or the reversal of soil degradation (soil quality improvement) attributable to tillage/cropping/land use systems. The community structure of soil microflora and fauna may well be a suitable indicator of soil quality.
This statement of work is general in its requirements. It might be described as the provision of tools for the Soil Conservation Advisor. It should address specific areas of interest such as microflora, vertebrate/invertebrate populations in soil related to the level and quality of organic matter, stability of soil structure, soil compaction or soil pH as examples. It should clearly identify the responsiveness of the parameter to the land use change and the importance of the parameter in soil management sustainability. Two constraints need to be observed. The time frame of the study does not permit establishment of tillage and cropping systems in the field, and the "motherhood" approach to describing soil quality factors would not be expected to yield definitive results. Therefore it is considered that the proposal will offer an extension to or enrichment of existing, ongoing work.
London Research Centre; Dr. A.D. Tomlin - $76,600.00 - Response of earthworms, soil biota, and soil structure to agricultural practices in corn, soybean, and cereal rotations
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This research has been published in:
Tomlin, A.D., R. Protz, R.R. Martin, D.C. McCabe and R.J. Lagace. 1993. Relationships amongst organic matter content, heavy metal concentrations, earthworm activity, and soil microfabric on a sewage sludge disposal site. Geoderma 57: 89 - 103.
Response of earthworms, soil biota, and soil structure to agricultural practices in corn, soybean, and cereal rotations
Dr. A.D. Tomlin, Dr. C.M. Tu, J.J. Miller and
The comparative effects of herbicide treatments, crop rotations and weed control practice on soil fauna, microflora, and soil microfabric features (e.g. soil particle size and shape) were measured in a multifactorial experimental design. Because of the extensive availability of nutrients in earthworm casts both at the surface and within the burrows, agronomic techniques enhancing or reducing earthworm populations have significant consequences for processes involving soil microflora and soil microfauna colonizing the burrows and for infiltration rates for air and water into soil.
Herbicide treatments reduced earthworm and some mite populations as much as machine cultivation for weed control. Continuous soybean rotations reduced abundance of earthworms, mites and springtails compared to rotations containing cereals and continuous corn rotations. Most of the faunal and microflora increases can be ascribed to increases in available soil organic matter.
Image analysis is a powerful tool which allows the physical associations of minerals, aggregates, organic matter and biotic components of soil to be measured in situ. Statistical analysis of image analyzed microfabric scenes taken from the resin impregnated soil blocks revealed differences in particle size (area) for both the herbicide and hand-hoed plots but not for the non-weeded control in all three crops. The particle shape parameter showed a similar result, except that there was no significant difference for herbicide treatment. This could be due to the 'homogenizing' effect of the weeds (or at least their roots) on soil physical structure. Using impregnated blocks, image analysis and spatial mapping of elements in earthworm faecal pellets in earthworm burrows it is possible to trace micro-scale interactions occurring in earthworm burrows, and compare cropping and tillage treatments on these interactions.
As a consequence of this research predictions can be made on the effect of tillage practices and weed control methods on populations of earthworms and mites with some confidence. Image analysis techniques of soil microfabric and fine soil structure were developed and measurements were made on the microfabric response to cropping, tillage and weed control methods and segregation of these differences with high statistical confidence was accomplished.
It now necessary to separate (tease apart) the contribution of agronomic practices from faunal/biotic contributions to soil microfabric. As a result of this research a method of accomplishing this goal by tracking identifiable microfabric-scale pedofeatures in the various treatments, and subjecting those features to fluorescence imaging and statistical analysis to establish their spatial distributions is now available. The imaging method is now feasible using fluorescence microscopy that incorporates an ultra-sensitive colour video camera and image analysis software. Further work could emphasize the relationship between fauna, soil structure, and plant roots in response to tillage treatments and weed control methods, for example.