Effect of dry‐heat sterilization on chemical properties of Puerto Rican soils

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Abstract
Few references explain the effects of dry‐heat sterilization on soil chemical properties. Yet dry heating at 121°C for 2 hours is the prescribed USDA Animal, Plant, and Health Inspection Service basic treatment for soils entering United States ports of entry. This study concerns the effects of air drying and dryheat sterilization on chemical properties of Puerto Rican soils, chiefly macronutrients and micronutrients, found after extracting with Mehlich‐1 and Olsen solutions. Results for dry heating are compared with reported results for other sterilization procedures. Dry heating did not significantly alter soil N, organic matter content, or soil bases. Depending on the extractant used, changes in P concentrations were significant. Results for micronutrient determinations were more variable and also depended on the extractant used after sterilization. Concentrations of Mn and Fe extracted from dry‐heated soils were significantly greater than concentrations extracted from air‐dried soils. Effects of dry‐heat sterilization on soil chemical properties generally followed results published elsewhere for steaming, exceptions depending on the extractant used. Published results from chemical sterilization established methylbromide as being closest to dry heat results.