Quantitative Physical Assessment of Organic Materials Used in Sports Turf Rootzone Mixes
- Edward L. McCoy
Peats and other organic materials are commonly used in sports turf rootzone mixes, yet few quantitative guidelines exist for selecting appropriate materials and incorporation rates. This study was conducted to assess the relative merits of organic sources and to identify a physical measure to assess the role of organic materials in rootzones. Five organic materials with organic contents ranging from 96 to 40% by weight and fiber contents ranging from 54 to 7% by weight were mixed with a mason sand at rates of 10, 20, and 30% by volume. Standard physical measures of bulk density, compressibility, saturated hydraulic conductivity, non-capillary porosity, and plant-available water revealed few differences between the organic sources for a given mixing rate. Regression relations between organic matter by weight and bulk density, and available water suggest that 3% organic matter (by weight) is required in order to attain bulk densities < 1.45 Mg m−3, and 3.5% organic matter is required for available water contents >0.2 m3 m−3. Water retention curves were used to determine the pore volume distribution for each organic source and mixing rate. The pore volume distributions were bimodal and revealed differences between the organic sources and mixing rates that were not apparent from standard physical tests. Analysis of these distributions suggest that organic sources having fiber contents >45% may be excessively coarse, and organic material incorporation rates should be selected so the final mix does not exceed 3.5% organic matter by weight.
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