Long-term effects of ammonium nitrate application on soil pH, and micronutrients in soil and bromegrass hay ·

Field experiments were established in 1968 at Crossfield, Alberta (Exp. 1) and in 1979 at Canwood, Saskatchewan (Exp. 2) to determine the long-term effect of annual applications of ammonium nitrate to bromegrass (Bromus inermis Leyss.) on forage yield and soil properties. Previous investigation on soil samples taken in 1983 (Exp. 1) and in 1989 (Exp. 2) showed shallow soil acidification from N application. The present study was conducted to find if shallow soil acidification influenced concentrations of Mn, Zn, Cu, Fe and Al in soil and in bromegrass forage. With increasing N fertiliser rates, soil pH was markedly reduced in the 0–5 cm layer and the amounts of extractable Mn, Fe and Al were increased in the 0–15 cm soil. Extractable Zn and Cu in soil tended to decrease with N application. The increase in concentration of Mn and Cu in forage was closely correlated with the decrease in pH from N fertilisation. The concentration of Fe and Al in forage decreased with N application, but there was little effect on Zn. The shallow acidification of soil from long-term N fertiliser application induced changes in micronutrients in soil and in the bromegrass forage grown on it.