Research review: Invited paper presented at the symposium “Mineralstoffversorgung, Tropischer Waldbiiume”, Bayreuth, Federal Republic of Germany, 13 July 1989

Fertilising Commercial Forest Species in Southern Africa: Research Progress and Problems (Part 1)

Published in: South African Forestry Journal
Volume 151, issue 1, 1989 , pages: 58–70
DOI: 10.1080/00382167.1989.9630507
Author(s): M.A. Herbert, South Africa, A., P.G. Schönau, South Africa

Abstract

Since the inception of forest fertiliser research in Southern Africa in 1926, eight eucalypt, six pine and four acacia species have been tested, encompassing a wide range of sites in summer, winter and uniform rainfall areas. Marked deficiencies of P, Mn and sometimes N, usually associated with hydromorphic and elluviated soils derived from sandstone, are easily diagnosed and corrected at planting or after canopy closure. On the other hand, ferralitic soils showing adequate growth rates respond mainly to applications of P and Ca but balanced for N and K at planting. However, requirements after canopy closure are difficult to determine, varying with site, species and stand development. Fertilising at planting promotes the development of a vigorous root system, which allows for continually improved growth. Thus responses increase with the effective rooting depth and soil water availability of sites, as well as being larger for the faster growing species. Hence MAI has been increased up to 11 m3/ha for eucalypts, 9 m3/ha for pine and 5 m3/ha for wattle. Similarly responses to fertilising after canopy closure appear greatest on deep soils with an adequate water supply.

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