EFFECT OF LEACHING ON SOIL PROPERTIES AND LUCERNE GROWTH FOLLOWING LIME AND GYPSUM AMENDMENTS TO A SOIL WITH AN ACID SUBSOIL

Amelioration of subsoil acidity was studied in pots containing reconstructed profiles. Gypsum or lime was placed in the A or B horizon, either with or without leaching, before growing lucerne. Liming the A horizon did not alter the pH, exchangeable Al3+, Al3+:Ca2+ ratio or root yield in the B horizon. The high lime application rate gave a pH of 7.8 in the A horizon. Lime addition to the B horizon increased pH, decreased Al3+ and Al3+:Ca2+, and increased root growth in that layer. Although gypsum increased exchangeable Ca2+, the pH was decreased and Al3+:Ca2+ only decreased slightly in the B horizon. Gypsum did not increase B horizon root yields, with or without leaching. The practical implications of these results are discussed.