EFFECT OF SUBSOIL ACIDITY AND FERTILITY ON THE GROWTH OF SEEDLING BLACK LOCUST AND GREEN ASH

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Abstract
Seedlings of Robinia pseudo-acacia and Fraxinus pennsylvanica lanceolata were grown on an acid infertile clay subsoil of the Lindley series. Four acidity levels (pH 4.3, 6.6, 6.9, and 7.7), and 3 fertility treatments (CK, NK, NPK), at each acidity level, were maintained. Both spp. showed a tremendous response to NPK at all pH levels, and growth on the NK treated soil and on the unfertilized soil was very poor. When P was added both species developed best at pH 4.3, and growth decreased as pH increased. When P was omitted growth increased with pH up to 6.9 and decreased again at pH 7.7. Green ash was tolerant of alkalinity due to CaCO3; black locust was intolerant. The results are interpreted in terms of phosphate availability. The fact that best growth occurred at pH 4.3 when phosphate was added was attributed to the relatively high base saturation of the original soil.