Scientific Paper

The Amelioration of Pinus patula Mortality on Former Agricultural Sites through Fertilisation: A Bioassay and Greenhouse Study

Published in: South African Forestry Journal
Volume 164, issue 1, 1993 , pages: 35–41
DOI: 10.1080/00382167.1993.9629375
Author(s): A.D. Noble, South Africa, A.W. Schumann, South Africa

Abstract

Recent expansion of the timber industry into areas previously used for agronomic production has, in many cases, resulted in poor growth of Pinus patula and P. elliottii seedlings and in certain instances complete stand failure. A bioassay study was initiated to evaluate the efficacy of soluble fertiliser in ameliorating the allelopathic effects of a water soluble corn (Zea mays) stover extract on the growth of lettuce (Lactuca sativa) seedlings. In addition, a potted trial was undertaken to evaluate the influence of nitrogen (N) and phosphorus (P) fertiliser sources in overcoming P. patula mortality on soil previously under agricultural production. Lettuce root mass and length was significantly reduced in the presence of the corn stover extract. However, partial recovery in root mass was achieved with additions of a soluble fertiliser. The main effect of fertiliser additions was the stimulation of lettuce shoot growth. The application of 100 mg/kg N to P. patula seedlings grown in pots resulted in highly significant increases in shoot growth. In addition, steam sterilisation and the use of various commercially available fertiliser sources resulted in significant increases in shoot growth over those treatments receiving no fertilisation. No significant response to P additions was observed. Results from foliar analyses clearly indicated that seedlings growing on untreated soil were N deficient (1,05% N). Foliar phosphorus was considered to be sufficient for adequate pine growth. The evidence indicates that the poor performance of P. patula seedlings growing on ex-agricultural lands can be amended by the application of N and that this may be the primary factor affecting stand establishment on these sites.

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