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Title: WITHIN SAMPLE VARIATION OF OXYGEN DIFFUSION RATE (ODR)

Author
item Logsdon, Sally

Submitted to: Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/19/2003
Publication Date: 8/1/2003
Citation: LOGSDON, S.D. WITHIN SAMPLE VARIATION OF OXYGEN DIFFUSION RATE (ODR). SOIL SCIENCE. 2003. V. 168. P. 531-539.

Interpretive Summary: Sustainable crop production depends on many factors, including good soil structure. Poor management results in degraded soil structure, typified by compaction, poor infiltration, or a shallow root system. Soil with good structure has many voids and loose regions that allow water infiltration, air exchange, and root growth. In this study a technique was developed that measures how far apart these loose soil regions are located, which can be used to measure soil structure. This technique will be helpful for indicating when soil is optimum for plant growth. This information will be used by scientists to identify and develop management practices which result in good soil structure.

Technical Abstract: Bulk density and hydraulic conductivity are often inadequate for characterizing soil structure. Alternatively this study investigated the oxygen diffusion rate (ODR) transect method to determine macropore spacing measured on intact samples. The ODR samples were collected three different ways to allow for horizontal transect measurements in the laboratory: 1) square soil samples excavated by hand and coated with paraffin on the sides, 2) round soil cores collected with a hydraulic sampler and contained in plastic liners, and 3) soil cores contained in square plastic holders made from plastic pop bottles. The samples with paraffin on the side were not stable when wet. The hydraulic probe had compressed the round cores, biasing the results. The samples in square plastic holders were stable when wet and not compressed during sampling. The half spacing between macropores determined by the ODR method ranged from 12 to 88 mm. The horizontal ODR transect method was useful to measure the spacing between aggregate or loose soil regions.