Effects of different ammonium nitrate levels on the amounts of exchangeable soil magnesium and applied magnesium in eight mineral soils

Abstract

Eight mineral soils (pH(CaCl2) 4.6—6.1, clay 4—65 %, org. C 1.9—5.7 %) were treated with ammonium nitrate and magnesium sulphate solutions adding 0, 20 or 40 mg mineral N and 0 or 4 mg Mg per 100 g soil. The soils were incubated for seven weeks at a constant temperatureof 20°C and a 25 % moisture level. After incubation, the exchangeable Mg was extracted with 1 M neutral ammonium acetate. The exchangeable magnesium content seemed to increase in some soils and to decrease in other soils with increasing ammonium nitrate amounts. The applied magnesium was fixed in a non-exchangeable form, especially at the highest ammonium nitrate level, in two clay soils taken from the rapakivi area of south-eastern Finland. In the other soils all applied magnesium was exchangeable irrespective of the amount of ammonium nitrate.