Acacia erioloba (synonym: Acacia giraffae) commonly known as Mpatsaka (Sotho),
Mokala (Tswana), Kameeldoring (Afrikaans) and camel Thorn (English) is an indigenous
leguminous tree that is adapted and commonly found in semi-arid savanna environments of South Africa. Being a leguminous plant, Acacia erioloba can fix atmospheric nitrogen into the soil. The objective of this study was to quantify the concentration of plant nutrients in soils beneath the canopies of Acacia erioloba trees in three land-use practices viz: fallow, grazing and bare land. Three trees were randomly selected in each land-use practice and soil samples were collected from beneath and beyond the tree canopies at depths of 0-10 and 10-20 cm.
Consistently, soil analysis revealed that the concentration of nutrients (N, P, Ca, Mg, Zn
and Mn) and soil biological properties (organic carbon, particulate organic matter,
microbial biomass nitrogen and microbial biomass carbon) among the land-use practices
were in the order: fallow > grazing > bare. Differences in the concentration of soil
nutrients between the land-use practices seemed to be influenced by management within
the land-use practices. Nitrogen, phosphorus, potassium and zinc were significantly higher
(p<0.05) in land under grazing while calcium and magnesium, were significantly higher
(p<0.05) under fallow land. As expected, bare land had the lowest concentration of all the
nutrients studied. The presence of animals around Acacia erioloba trees contributed to
higher concentration of nutrients in land under grazing. The differences in the values of
biological properties were considered to be likely due to higher plant biomass on the
topsoil compared to the subsoil that increased the microbial activity. The improved
biological properties are thought to have improved the nutrient concentration through
processes such as mineralisation of nutrients from organic matter.
With the exception of phosphorus (P), potassium (K) and zinc (Zn), concentration of all
other nutrients (N, Ca, Mg and Mn) was not significantly different (p<0.05) in soil from
beneath the tree canopy and those from beyond the tree canopies in all land-use practices.
Topsoil (0-1 0 cm) had, significantly higher (p<0.05) concentration of all nutrients and
biological properties that were measured compared to the sub soil (10-20 cm). This was
attributed to the fact that much of the decomposition of soil organic matter takes place on
the surface layer of the soil where most of the organic materials are added. Nutrient
uptake from deep soil layers by roots of the trees may be another important mechanism
that could enrich surface soils beneath Acacia erioloba tree with nutrients.
The availability to a wheat crop of the nutrients found beneath the canopies of Acacia
erioloba was evaluated using a "Neubauer" seedling technique in a glasshouse. Wheat
seedlings were grown into PVC pots filled with soils collected from beneath and beyond
the tree canopies. The wheat that was grown in soils collected beneath Acacia erioloba
trees had significantly higher (p<O.OS) growth ~d nutrient uptake than that grown in soils
from beyond tree canopies. Plant height, dry matter yields and nutrient uptake by the
wheat seedlings were in the order fallow>grazing>bare land. The plant height were 20.9,
16.4 and 14.2 cm for fallow, grazing and bare, respectively. This was attributed to the high
accumulation of organic matter from different sources such as leaf litter, grass residues and animal wastes under fallow and grazing land. Fallow and grazing promotes large organic matter inputs and therefore create conditions that favour rapid decomposition of organic matter and mineralisation of nutrients.
Correlation coefficients between soil nutrients and nutrients in the tissues of wheat show
that there was a strong and significant relationship between the two. It was suggested from these results that Acacia erioloba trees has a potential to be used in agroforestry systems within the farming systems of the small-scale farmers in the semi-arid savanna ecosystem of the North-West Province. Such systems could include agrislviculture and
sylvopastoral. If Acacia erioloba trees are to be included in agroforestry systems, the
densities need to be increased. This would imply increasing their propagation. More
techniques of propagating the tree need to be researched. The nitrogen fixing potential of
Acacia erioloba needs to be thoroughly investigated. / Thesis (M.Sc (Agric.) North-West University, Mafikeng Campus, 2003
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:nwu/oai:dspace.nwu.ac.za:10394/11322 |
| Date | January 2003 |
| Creators | Murovhi, Romeo Nndamuleleni |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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