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Section 779.21 (a) Continued. <br />• 26.1 ppm. Other topsoils in Colorado were found to contain an <br />average of 14.3 DTPA iron (Follett and Lindsay, 1970). Ludwick, <br />et. al. (1976) reports that soils containing more than 4.5 ppm DTPA <br />iron are adequate for optimum plant growth. The toxicity levels for <br />DTPA iron have not been established to date (Dollhopf, et. al., <br />1977). <br />Manganese. Heil (1976) found total manganese values on Energy Afine <br />No. 1 to range from 340 ppm to 695 ppm, with an average of 487 ppm. <br />Other sites sampled in northwest Colorado ranged from 55 ppm to <br />1750 ppm. Follett and Lindsay (1970) reported that total manganese <br />values in Colorado soils ranged from 68 to 1340 ppm. DTPA manganese <br />values were reported by Heil (1976) to range from 2.0 ppm to 20.0 <br />ppm, with an average of 9.9 ppm. Berg (1973) reported a manganese <br />value of 47 ppm. The Montana Department of State Lands (Dollhopf, <br />et. al., 1977) reports that overburden DTPA manganese values <br />• greater than 60 ppm are "suspect" for toxicity. Since manganese <br />values did not exceed 20 ppm, nu manganese toxicities are probable <br />in the permit area. Follett and Lindsay (1970) report that the <br />critical soil test level of DTPA manganese is 1.0 ppm indicating <br />that all manganese levels in the area are adequate for normal plant <br />growth of this essential element. <br />Copper. Total copper values were reported by Heil (1976) to range <br />from 8.2 to 24.8 ppm, with an average of 15.0 ppm. DTPA copper <br />levels were found to range frum 0.2 ppm to 1.1 ppm, with an average <br />of 0.6 ppm. Berg (173) reported a copper value of 1.3 ppm on soil <br />collected within the permit area. Follett and Lindsay (1970) <br />report that the DTPA copper contents in Colorado ranged from 0.14 <br />ppm to 3.68 ppm, with an average 0.90 ppm. Suspect levels for DTPA <br />copper levels for overburden in Montana are over 40 ppm (Dollhopf, <br />et. al., 1977). Therefore, no toxicities are expected as a result <br />of copper concentrations. Follett and Lindsay (1970) report that <br />. the critical soil test level for DTPA copper is 0.20 ppm indicating <br />779-298 <br />