Alternative practices for optimising soil quality and crop protection for macadamia orchards, Limpopo Province, South Africa.

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dc.contributor.advisor Crafford, J. E.
dc.contributor.advisor Gliessman, S. R.
dc.contributor.advisor v. d. M. Louw, S.
dc.contributor.author Steyn, Jakobus Nicolaas
dc.date 2019
dc.date.accessioned 2019-10-02T13:51:16Z
dc.date.available 2019-10-02T13:51:16Z
dc.date.issued 2019-09-30
dc.identifier.citation Steyn, Jakobus Nicolaas (2019) Alternative practices for optimising soil quality and crop protection for macadamia orchards, Limpopo Province, South Africa. University of Venda, South Africa.<http://hdl.handle.net/11602/1409>.
dc.identifier.uri http://hdl.handle.net/11602/1409
dc.description Department of Ecology and Resource Management en_US
dc.description PhDENV
dc.description.abstract The main aim of the research was to contribute means for converting conventional, high-input production systems to more sustainable ecological systems, thereby improving the sustainability of macadamia production and ultimately contributing to food security. This was achieved by a) investigating the potential use of cover crops and compost to enhance soil quality in macadamia orchards and b) investigating the potential use of use of cover crops and orchard heterogeneity to control stinkbug pests that target macadamia crops. Field experiments were conducted in three phases: phase one tested the potential of six cover crops for crop protection (as trap crops) and simultaneously for soil restoration or fertility enhancement purposes in macadamia orchards. Phase two repeated the trials of phase one (both soil restoration and trap crops) but with modifications to both categories. Soil restoration treatments were conducted with trees which were growing in what appeared to be healthy soils, and then repeated with trees in the same orchard where the topsoil had been degraded (totally removed) by agricultural operations. The third phase repeated the trap crop trials only, but this time on three different study areas (all commercial farms) with the single cover crop which performed the best as a trap crop during phase two. Trials were modified from the first to the last phase to overcome practical implementation problems encountered along the way and to adapt to local conditions experienced in the commercial macadamia farming systems which served as research sites. Diversity of natural orchard vegetation was enhanced in phase three to improve conditions for natural predators as part of the trap crop treatments in the last phase and cover crops were finally first composted and then returned to the root zones of the macadamia trees as part of the soil quality enhancement treatments in the second phase. The results from the trap crop trials shows a significant effect of trap crops combined with increased orchard diversity in reducing unsound kernel percentages caused by stinkbug pests and demonstrate that trap crops combined with an increase in orchard diversity could be utilized in macadamia orchards as a more sustainable alternative to inorganic pesticides against the stinkbug complex. The most notable changes in the soil that took place with soil quality enhancement treatments were the significant increases in soil phosphorous content and pH which resulted not in an improvement in soil quality in terms of these two indicators but revealed an important issue about the use of compost containing animal manure originating from dairies or feedlots. In summary however, it was clear that although not all the soil quality indicators that were employed to assess changes in the soil with compost treatments improved significantly, a holistic consideration of all indicators portrays an overall improvement which was particularly significant in the degraded soil plots where the topsoil had been removed by prior agricultural activities. en_US
dc.description.sponsorship NRF en_US
dc.format.extent 1 online resource (117 leaves, color illustrations)
dc.language.iso en en_US
dc.subject Cover crops en_US
dc.subject Trap crops en_US
dc.subject Ecological sustainability en_US
dc.subject Soil quality en_US
dc.subject Crop protection en_US
dc.subject Habitat en_US
dc.subject Heterogeneity en_US
dc.subject Compost en_US
dc.subject Macadamia en_US
dc.subject.ddc 634.50968257
dc.subject.lcsh Soil conditioners -- South Africa -- Limpopo
dc.subject.lcsh Macadamia nut -- South Africa -- Limpopo
dc.subject.lcsh Nuts -- South Africa -- Limpopo
dc.subject.lcsh Cover crops -- South Africa -- Limpopo
dc.subject.lcsh Compost -- South Africa -- Limpopo
dc.subject.lcsh Soil amendment -- South Africa -- Limpopo
dc.title Alternative practices for optimising soil quality and crop protection for macadamia orchards, Limpopo Province, South Africa. en_US
dc.type Thesis en_US

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