INCREASE OF SOIL ACIDITY AND CONCENTRATIONS OF EXTRACTABLE ELEMENTS BY 1 M AMMONIUM NITRATE AFTER STORAGE OF DRY SOIL FOR UP TO 5 YEARS AT 22°C

• Published in: Communications in soil science and plant analysis 2001-04, Vol.32 (5-6), p.675-684
• Main Authors: Ogner, Gunnar, Randem, Guro, Remedios, Gabriele, Wickstrøm, Torild
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Biological and medical sciences; Chemical, physicochemical, biochemical and biological properties; Fundamental and applied biological sciences. Psychology; Mineral components. Ionic and exchange properties; Physics, chemistry, biochemistry and biology of agricultural and forest soils; Soil science
• ISSN: 0010-3624; 1532-2416
• DOI: 10.1081/CSS-100103900

Analyses of forest soils are widely used to monitor the effects of human activity on our environment. The overall quality of analytical data must, therefore, be sufficient to answer questions with regard to environmental changes taking place throughout several decades. Three horizons of an air-dried forest soil, was stored at 22±3°C, 3°C and −21°C for up to 1,842 d to monitor its stability during storage. At room temperature, 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 NH 4 NO 3 increased by 94%, 62% and 68%, respectively, after 1,842 d. A corresponding increase in exchangeable cations [aluminum (Al), barium (Ba), calcium (Ca), magnesium (Mg), manganese (Mn), strontium (Sr), and zinc (Zn)] ranged from 11 to 23%. Storage at 3°C resulted in a decrease in pH only for mineral soil (10 -15 cm layer). At −21°C, no changes in any of the soil-extractable components were found. 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 therefore not exceed 50 d for air-dried forest soil samples stored at room temperature. We suggest that longterm storage of air-dried forest soil samples should take place at −20°C or lower, preferably in airtight containers, to ensure the stability of organic and inorganic bound elements, especially C, P, and S.