Total Trace Elements and DTPA-Extractable Micronutrients in the Benchmark Soils of Oklahoma.

Baseline trace element and plant available micronutrient levels are necessary for proper decision making in both agricultural and environmental fields. This study was conducted to establish the baseline levels of total trace metals and DTPA extractable boron (B), Iron (Fe), zinc (Zn), copper (Cu), and manganese (Mn) in 28 benchmark soils of Oklahoma and to determine soil factors affecting those levels. The 28 benchmark soils of Oklahoma include six soil orders and represent the major land use resource areas of the state. Total concentrations of soil metals and B were determined by digestion with nitric acid and hydrogen peroxide. Soil factors such as pH, Mehlich 3 phosphorus (M3P), clay content, and organic carbon (OC) were also analyzed. DTPA-extractable Fe had a significant (p < 0.01) inverse relationship to soil pH while B had a significant direct relationship to pH. The relationships of B and Cu to clay content were highly significant. Copper was found to have a significant relationship with organic carbon (p < 0.01) as was Fe and Mn (p < 0.05). Zinc and copper both increased significantly as M3P increased. Soil properties controlled micronutrient availability and total trace metal concentrations of a soil.