| Summary: | Thesis (MSc)--Stellenbosch University, 2005. === ENGLISH ABSTRACT: The agricultural sector in South Africa relies heavily on the use of pesticides to protect
crops against pest organisms. Pesticides can affect non-target organisms such as the
meso- and macrofauna in the soil detrimentally. Since these organisms play an important
role in the processes of mineralization and decomposition in the soil and contribute to soil
fertility, it is important that they are protected. A large amount of published literature
exists on the biological importance of soil meso- and macrofauna and the effects that
various agricultural practices have on them.
The main aim of this study was to investigate the influence of agricultural practices on
the abundance and diversity of meso- and macrofauna in different vineyard soils. A
comparative study was conducted of an organically managed, conventionally managed
and an uncultivated control soil. A secondary aim was to determine the effect of these
agricultural management practices on the biological activity of these animals.
Soil samples were taken, from which mesofauna (Collembola and Acari) were extracted
with a modified Tullgren extractor, identified and counted. Earthworms were extracted
from the soil using hand sorting methods. Soil parameters such as pH, water holding
capacity, organic matter content, soil texture and soil respiration were determined. Bait
lamina and litter-bags were also used to help determine the biological activity within the
soil.
The mesofauna diversity was quantified using the Shannon Weiner diversity index, as
well as a diversity index described by Cancela da Fonseca and Sarkar (1996).
Differences in abundance of both the meso-and macrofauna were statistically measured
using ANOVA's. Biological activity results were also interpreted using ANOV A's.
Results indicate that the abundance of the meso fauna was the highest at the organically
treated vineyard soil and lowest in the conventionally managed soil where pesticide
application took place. The earthworms also showed the same trend as the mesofauna, but were much more influenced by seasonal changes. Biological activity, according to
the bait lamina and the litter-bag results, was higher in both the conventionally and
organically managed soils than in the control, but no statistical significant differences
were found between the two experimental soils. The soil respiration (C02-flux), also
indicating biological activity, was highest in the organically treated soil and lowest in the
conventionally treated soil.
The different sampling techniques used gave variable results and although the organically
managed soil proved to have higher abundances of both meso- and macrofauna, the
biological activity did not show the same trends. In conclusion the data did not give
enough evidence as to whether organic management practices were more beneficial than
conventional management practices for the maintenance of soil biodiversity. === AFRIKAANSE OPSOMMING: Die Suid Afrikaanse Landbousektor steun hewig op die gebruik van verskillende
chemiese pestisiede om oeste teen pes organismes te beskerm. Pestisiede kon ook
verskeie ander nie-teikenorganismes soos die meso- en makrofauna in die grond negatief
affekteer. Hierdie organismes behoort beskerm te word omdat hulle 'n belangrike rol
speel in grondprosesse soos mineralisering, en die afbreek van organiese materiaal.
Hierdie organismes dra ook by tot die vrugbaarheid van die grond. Daar is heelwat
gepubliseerde literatuur beskikbaar wat verband hou met die biologiese belangrikheid van
grond meso- en makrofauna en die effekte wat verskeie landbou behandelings op hulle
het.
Die primêre doel van hierdie studie was om vas te stel watter invloed konvensionele
landboupraktyke op die hoeveelheid en diversiteit van meso- en makrofauna in
verskillende wingerdgronde het. 'n Vergelykende studie is gedoen om wingerdgronde
wat konvensioneel en organies behandel is sowel as 'n onbehandelde kontrolegrond met
natuurlike plantegroei met mekaar te vergelyk. 'n Sekondêre doel van hierdie studie was
ook om die effek van die verskillende boerderymetodes op die biologiese akitiwiteit in
die grond te ondersoek.
Grondmonsters is geneem, waaruit die meso fauna (Collembola en Acari) deur middel van
'n aangepaste Tullgren ekstraktor ge-ekstraheer, geïdentifiseer en getel. Die erdwurms is
deur middel van handsorteringsmetodes versamel. Die volgende grond parameters is
gemeet: pH, waterhouvermoë, organiese materiaal inhoud, grondtekstuur en
grondrespirasie. "Bait lamina" en "litter bags" is ook gebruik om biologiese aktiwiteit in
die grond te bepaal.
Die diversiteit van mesofauna is bepaal met die Shannon Weiner diversiteitsindeks, as
ook 'n diversiteitsindeks wat deur Cancela da Fonseca en Sarkar (1996) ontwikkel is. Die
resultate van beide die meso- en makrofauna hoeveelhede in die verskillende
wingerdgronde is met mekaar vergelyk deur van ANOV A's gebruik te maak. Die resultate van die biologiese aktiwiteit is ook deur middel van ANOVO's statisties met
mekaar vergelyk.
Die resultate het aangetoon dat die hoeveelheid mesofauna die hoogste in die organies
behandelde grond en die laagste in konvensionele grond was. Die erdwurms het
dieselfde patroon as die mesofauna getoon, maar is baie meer deur seisoenale faktore
geaffekteer, bv. reënval. Volgens die resultate van die "bait lamina" en die "litter bags"
was die biologiese aktiwiteit in die grond hoër in beide die eksperimentele grond as in die
kontrolegrond. Die grondrespirasie (C02-puIs) was hoër in die kontrolegrond as in die
ander eksperimentele gronde.
Daar was groot variasie tussen die resultate wat met die verskillende tegnieke verkry is en
alhoewel die organiese perseel hoër hoeveelhede van beide meso- en makrofauna gehad
het, het die biologiese aktiwiteit nie dieselfde tendens gewys nie. Vanuit die data wat
verkry is kon daar dus nie met sekerheid afgelei word dat organiese boerderymetodes
beter vir die biodiversiteit van gronde,soos hier gemeet, is as konvensionele
boerderymetodes nie.
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