Thesis (MScFor)--Stellenbosch University 2002. / ENGLISH ABSTRACT: One of the greatest .limitations to the productivity of a plantation forest is poor
nutrient status of the soil. Empirical application of corrective treatments are
marginally successful in some cases, but because of limited understanding of the soiltree
system, most nutritional problems go unnoticed or are accepted as a conceivable
growth constraint. The aim of this investigation was to identify nutrient growth
problems through field observations and to determine means of confirming these
nutrient imbalances.
Poor and abnormal growth of pine trees in the following areas were investigated:
(i) The North Eastern Cape: Ugie and Maclear Districts
(ii) The Natal Midlands: Mooi River area
(iii) Mpumalanga: .Graskop and Kaapsche Hoop areas
(iv) Southwestern Cape: Jonkershoek Plantation
The study was conducted as nursery trials at the University of Stellenbosch and field
trials at the various locations. Soils from the different regions were collected and used
as growing media to test the growth response of five timber species (Pinus patula, P.
elliottii, P. taeda, P. greggii and Eucalyptus nitens) under controlled conditions to
various nutrient treatments. Indicator plants (cauliflower and soya) were included in
these bio-assays. In the field trials nutrients were applied to seedlings and established
stands of various ages by means of foliar and soil application.
In the nursery trials and the trials where seedlings were planted in the field, plant
performance was measured by quantitative means. The reaction of established stands
to nutrient treatments were however less vigorous and qualitative means (e.g. colour
changes) were used for assessment.
Field observations in the North Eastern Cape and the Natal Midlands indicated
possible boron, iron and molybdenum deficiencies and thus the work concentrates on
these elements. Foliar and soil analyses reinforced these observations with marginal to
deficient levels for boron and molybdenum being detected. The yellowing of foliage
during the dry season was symptomatic of ineffective nitrogen assimilation and pointed to a molybdenum deficiency while seasonal growth tip dieback, resm
exudation, sinuous tree limbs and bushy trees were classical boron deficiency
symptoms. Potted trials indicated positive reaction to the application of boron and
molybdenum deficiency symptoms were observed on indicator plants. Conclusive
evidence of a boron deficiency in some of the pot trials, the planted field trials and the
tree evaluation field trials remain elusive due to toxicity experienced as a result of an
over-application of the nutrient. The occurrence of multiple deficiencies (phosphorous
and calcium) further complicated the findings.
The Mpumalanga observations indicated severe nutrient imbalance due to manganese
toxicity (strong iron antagonism). The discolouring of the foliage on some sites
towards the end of the winter was thought to be an induced molybdenum deficiency
on the weathered and acidic red soils. Positive reaction to molybdenum application
occurred in a single. tree evaluation trial, but because of soil oxidisation during
collection, the effect of manganese toxicity was diluted in the pot trials. Foliar
analyses indicated that foliar application of iron was unsuccessful and that other
means should be considered to ensure uptake of this nutrient. / AFRIKAANSE OPSOMMING: Die lae vrugbaarheid van grond is een van die grootste beperkings tot die
produktiwiteit van plantasie bosbou. Empiriese toedienings van kunsmisstowwe is in
sekere gevalle suksesvol tot die bekamping van onvrugbaarheid. Weens gebrekkige
kennis t.o.v die grond-boom sisteem word baie van die voedingstof probleme egter
onkundig oorgeslaan' of word dit as natuurlike beperking in die produksie konteks
aanvaar. Die doel van hierdie ondersoek was om swak boomgroei in die veld waar te
neem en om bevestigende metodes te vind waarmee hierdie probleme as
voedingstoftekorte geëien kan word.
Swak en abnormale boomgroei van denne is in die volgende gebiede ondersoek:
(i) Die Noordoos Kaap: Ugie- en Maclear Distrikte
(ii) Die Natal Middelande: Mooirivier area
(iii) Mpumalanga: Graskop- en Kaapsche Hoop areas
(iv) Suidwes Kaap: Jonkershoek Plantasie
Die ondersoek is uitgevoer as kwekery proewe by die Universiteit van Stellenbosch
en as veldproewe in die onderskeie areas. Grond is uit die verskilende gebiede
versamel en as groeimeduim gebruik om die groei-reaksie van vyf verskillende
houtspesies (Pinus patula, P. elliottii, P. taeda, P. greggii en Eucalyptus nitens) onder
beheerde klimaatsomstandighede te ondersoek. Daar is ook gebruik gemaak van
indikator spesies (blomkool en soya) vir diagnose van visuele tekort simptome. Beide
saailinge en reeds gevestigde bome is in die veldproewe gebruik. Voedingstowwe is
by aanplanting toegedien, of in die geval van groter bome, as blaar- of
grondtoedienings.
Waar dit moontlik was (meestal in die geval van die saailinge) is die reaksie op die
toegediende voedingstowwe met kwantitatiewe metodes bepaal. Daar moes egter van
alternatiewe kwalitatiewe metodes gebruik gemaak word om die reaksie by die ouer
en groter bome te bepaal. Gevolglik is verandering in bladkleur t.o.v. 'n basiskleur
onder andere as maatstaf gebruik. Waarnemings van swak boomgroei in die Noordoos Kaap en die Natal Middelande
het gedui op moontlike boor, yster en/of molibdeen tekorte. Lae vlakke van hierdie
elemente in blaar- en grondanalises het hierdie waarnemings bevestig. Die geel
verkleuring van die naalde gedurende die droë seisoen is simptomaties van
oneffektiewe stikstof assimilasie en dui op 'n molibdeen tekort. Die waarneming van
seisoenale terugsterwing van groeipunte, gebuigde stamme en takke, gomuitskeiding
en bome met bosagtige voorkoms is eienskappe van 'n boor tekort. In die potproewe
was daar positiewe reaksie op die toediening van boor en tekort simptome van
molibdeen is in die indikator plante waargeneem. In van die potproewe, die saailing
veldproewe en ander veldproewe kon daar egter nie uitsluitsel tot die effektiwiteit van
boor gevind word nie aangesien toedienings te heftig was en toksisiteit ervaar is.
Diagnose van enkel element voedingstof tekorte word bemoeilik deur van die proewe
wat ook dui op veelvoudige voedingstoftekorte (veral fosfaat en kalsium).
In Mpumalanga is daar waargeneem dat drastiese voedingstof wanbalanse a.g.v.
mangaan toksisiteit aanwesig is (veral 'n sterk Fe antagonisme). Die bladverkleuring
op sekere proefopstande aan die einde van die winter is ook 'n aanduiding van
geïnduseerde molibdeen tekorte wat op die verweerde en suur rooi gronde van die
omgewing verwag kan word. Daar was dan ook positiewe reaksie op die toediening
van molibdeen, hoewel slegs byeen proefopstand. Die inherente nadeel van
potproewe is op die mangaanryk gronde geopenbaar deurdat belugting (gedurende
grond versameling) die effek van mangaan toksisiteit verminder het. Die gebruik van
blaaranalises is ook voordelig aangewend om te bepaal dat die toediening van yster as
blaartoediening onsuksesvol was en dat ander metodes ondersoek moet word om
opname van die element te verseker.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/52897 |
| Date | 03 1900 |
| Creators | Buchler, K. (Konrad) |
| Contributors | Ellis, F., Stellenbosch University. Faculty of Agrisciences. Dept. of Forest and Wood Science. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 166, [44] p. : ill. |
| Rights | Stellenbosch University |
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