The objective of this study was to investigate the effects of land use and management practice on the
soil organic matter content and the size, activity and diversity of the microbial biomass. These effects
were investigated using samples taken from the top (0-10 cm) layer of the soils from long-term
agricultural managements including natural grassland, maize under conventional (maize CT), maize
under zero tillage (maize ZT), annual ryegrass, Eucalyptus, Pinus, and permanent kikuyu pasture. The
natural grassland was used as a control since records indicated that no agricultural activity had ever
been exerted on the soil. The measurements used to investigate these effects included soil organic C,
total N, soil pH, microbial biomass C, basal respiration rate, microbial quotient, metabolic quotient,
dehydrogenase activity, fluorescein diacetate (FDA) hydrolysis, arginine ammonification rate,
arylsulphatase activity and acid and alkaline phosphatase activities. The microbial functional diversity
was measured using the Biolog Ecoplate and catabolic response profiles methods.
Soil organic Cand total Nwere lowest under maize CT, followed by maize ZT and annual ryegrass and
were higher under natural grassland, Eucalyptus and Pinus plantations while permanent kikuyu pasture
had the highest values. The other analyses, namely microbial biomass C, basal respiration rate, FDA
hydrolysis, arginine ammonification rate and arylsulphatase activity also followed the same pattern.
Annual cultivation was responsible for a decrease in microbial biomass C, basal respiration rate and
enzyme activity, principally because there was an appreciable decrease in soil organic matter content.
Conversely, permanent pasture, Eucalyptus and Pinus plantations increased appreciably the amount of
organic C and consequently, promoted the size and activity of the microbial biomass in the soils. The principle component scores showed that management practices affected the microbial functional
diversity because different treatments were found in separate zones of the principle component spaces.
The regression analysis showed that the variation in the PC1 and PC2 scores was correlated with the
variation in soil organic C, exchangeable acidity, extractable P and exchangeable K and Mg. In addition,
richness, evenness, Shannon, and Simpson diversity indices showed that any management practice
affects the dynamics of soil microbial diversity. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2002.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ukzn/oai:http://researchspace.ukzn.ac.za:10413/4911 |
| Date | January 2002 |
| Creators | Nsabimana, Donat. |
| Contributors | Wallis, Frederick Malcolm. |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
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