EFFECTS OF LONG-TERM N FERTILIZER-INDUCED ACIDIFICATION AND LIMING ONMICRONUTRIENTS IN SOIL AND IN BROMEGRASS HAY

A field experiment was initiated in 1968 at Crossfield, Alberta to det ermine the effects of 27 years of fertilization with ammonium nitrate (0, 56, 112, 168, 224, and 336 kg N ha(-1)yr(-1)) to bromegrass (Bromu s inermis L.) on soil acidification, and on micronutrient concentratio ns in soil and in hay. A portion of each N plot was treated with surfa ce-applied finely-ground calcium carbonate (referred to as lime) in 19 91 at rates to bring soil pH (in H2O) near 7.0, and both the limed and non-limed portions were sampled for soil and hay in the autumn of 199 4. Soil pH was 6.85 in the 0-5 cm layer when no N was applied, but pH values were markedly reduced with increasing N rates, with pH 4.10 or less when N rate was 168 kg N ha(-1) or more. There was also a drastic depression in soil pH from N application in the 5-10 cm layer. In the 10-15 cm soil layer, pH decreased only at the highest N rate (336 kg N ha(-1)). Liming increased markedly soil pH in the 0-5 cm layer. The increase of CaCl2-extractable Al and DTPA-extractable Fe in soil was c losely correlated with the decrease in soil pH from N fertilization. L iming decreased extractable Al in soil in the 0-5 and 5-10 cm layers, while increasing extractable Fe in the 0-5 cm and decreasing it in the 5-10 and 10-15 cm layer. In the 0-5 cm soil layer, DTPA-extractable M n first increased with N application at 112 kg N ha(-1) and then decre ased sharply beyond that N rate. In the 5-10 cm layer, extractable Mn increased at 168 and 224 kg N ha(-1) rates, while in the 10-15 cm laye r it maximized at the 336 kg N ha(-1) rate. Liming had no effect on ex tractable Mn in the 0-5 cm soil layer, but it decreased Mn in the 5-10 and 10-15 cm layers. There was little or no effect of N fertilization and liming on extractable Zn and Cu in soil. The bromegrass hay yield ed more as the rate of N was increased up to 224 kg N ha(-1), but yiel d then decreased with the highest N rate (336 kg N ha(-1)). Liming inc reased hay yield, but only in the third and fourth year after liming a nd then only on those treatments which had received 168 kg N ha(-1) or more. The concentration of Fe and Al in hay decreased with N applicat ion, but concentration of Zn and Mn in hay increased. There was little effect of N fertilizer on Cu. Liming decreased the concentration of F e, AI, and Mn in forage, but it had little effect on Cu and no effect on Zn. (C) 1998 Elsevier Science B.V. All rights reserved.