Increase of soil acidity and concentrations of extractable elements by 1 Mammonium nitrate after storage of dry soil for up to 5 years at 22 degreesC

Analyses of forest soils are widely used to monitor the effects of human ac tivity on our environment. The overall quality of analytical data must, the refore, be sufficient to answer questions with regard to environmental chan ges taking place throughout several decades. Three horizons of an air-dried forest soil, was stored at 22 +/-3 degreesC, 3 degreesC and -21 degreesC f or up to 1,842 d to monitor its stability during storage. At room temperatu re, soil acidity increased and soil pH in water decreased by 0.1 to 0.3 pH units depending upon the soil horizon. The amount of carbon (C), phosphorus (P), and sulfur (S) extracted by 1 M NH4NO3 increased by 94%, 62% and 68%, respectively, after 1,842 d. A corresponding increase in exchangeable cati ons [aluminum (Al), barium (Ba), calcium (Ca), magnesium (Mg), manganese (M n), strontium (Sr), and zinc (Zn)] ranged from 11 to 23%. Storage at 3 degr eesC resulted in a decrease in pH only for mineral soil (10-15 cm layer). A t -21 degreesC, no changes in any of the soil-extractable components were f ound. The amount of elements released by acid digestion did not change with storage time or temperature. The results indicate that biological and/or chemical activity degrades soil organic matter during storage at room temperature. Storage time should the refore not exceed 50 d fur air-dried forest soil samples stored at room tem perature. We suggest that longterm storage of air-dried forest soil samples should take place at -20 degreesC or lower, preferably in airtight contain er. to ensure the stability of organic and inorganic bound elements, especi ally C, P, and S.