LONG-TERM EFFECTS OF ORCHARD SOIL-MANAGEMENT ON TREE VIGOR AND EXTRACTABLE SOIL NUTRIENTS

Bisbee Delicious apple trees on M.26 (Malus domestica Borkh.) rootstock were planted in 1982 on a neutral pH, loamy-sand soil and were subjected to five soil management-fertilizer regimes until 1989. Orchard floor vegetation control with herbicides was required to maximize tree growth. Annual application of P at 50 kg ha-1 and K at 100 kg ha-1 from 1984 to 1989 increased extractable soil P and K to the 40-cm depth but did not appear to increase tree vigor. Orchard floor vegetation maintained extractable soil Ca and Mg levels compared to vegetation control treatments.