DRIS EVALUATION OF TEAK (TECTONA-GRANDIS LF) MINERAL-NUTRITION AND EFFECTS OF NUTRITION AND SITE QUALITY AN TEAK GROWTH IN WEST-AFRICA

The objective of the investigation was to study the site variables con trolling teak yield (Tectona grandis Linn.fil.) and to establish guide lines for the selection of high productivity sites in Benin, Cote d'Iv oire, Liberia, Nigeria and Togo. Depending on stand age, soil and regi on, between 70 and 90% of the variation in tree growth (site index. SI ) could be explained by the supply of nitrogen, the root-available soi l depth and precipitation. Diagnostic folia; analysis for a broad rang e of elements was carried out in all plantations with the exception of Nigeria. This showed that in 20% of the stands, various deficiency sy mptoms occur, and in an additional 40%, hidden demand of at least one nutrient is apparent. According to the Diagnosis and Recommendation In tegrated System (DRIS), the most deficient nutrients besides N are Ca and P, while in 45% of all stands there is a relative Al excess. Recom mendations for the evaluation and classification of site quality and t he number of trees sampled for foliar analysis are given.