1. Improving poor performing grapevines by means of root pruning or mulching

Researcher: E. Moffat

Spatial variability and grapevine underperformance are common challenges faced by grape growers. Root pruning is currently carried out as a practice based on growers’ practical experience, and not on scientific evidence. Furthermore, it is not common practice to incorporate organic matter during a root pruning action to improve soil physical, as well as biological conditions. Incorporated organic matter, e.g. of which compost is most commonly used, has a wide array of benefits to soils. The water saving effects of organic mulches are well documented. However, further research into the required thickness of compost mulched would be valuable to growers.

The first field trial intends to investigate the effect of incorporating organic matter during the root pruning action on the soil environment and grapevine performance. If this practice proves to be successful, it would establish the ground work for further investigation into the costs and most efficient implement to incorporate compost during root pruning. The second field trial aims to establish the ideal compost mulch thickness at which water-saving benefits are achieved.

 

2. Screening of locally available rootstocks for nematode and drought resistance

Researcher: S. Booi

The South African grape industry is currently dependent on a small selection of grapevine rootstocks. Most commercial grapevine rootstocks are susceptible to most nematode species found in South Africa. When nematodes feed on the roots of a grapevine, the ability of the vine to absorb water and nutrients is restricted, thereby resulting in low vigour and much reduced yield. The damage that is caused by plant-parasitic nematodes in SA may be estimated close to R2 billion. Another challenge is the phasing out of highly toxic nematicides and in turn, a need for environmentally friendly and pesticide-free control methods. There is therefore, a drive towards breeding for resistance.

In this research project, approximately 20 locally available grapevine rootstocks (imported and locally bred) will be screened for resistance to nematode pests found in South African vineyards, under controlled glasshouse conditions. Nematodes that will be included in the study are ring, dagger, root lesion and root-knot nematodes. Furthermore, these rootstocks will also be screened for drought tolerance.

The study would assist in the identification of major rootstocks that the grapevine industry can rely on for future vineyard establishment.

 

3. Pilot-scale treatment of winery wastewater

Researcher: G.O. Sigge

Several biological winery wastewater treatment methods have been proposed, including chemical, physico-chemical, aerobic and anaerobic methods. Anaerobic digestion (AD) has been shown to be a viable option for many food and beverage processing wastewaters, including winery wastewater. A few AD processes have been successfully applied in the wine industry, but very little literature is available on the anaerobic sequencing batch reactor technology, even though it has the potential to suit winery wastewater’s seasonal production. This technology was investigated in a recent Winetech project. The use of the novel AnSBR to treat a synthetic winery wastewater substrate over a range of 1 000 – 7 000 mg/ℓ was found to be feasible. It was recommended that the AnSBR process be upscaled into a pilot scale set-up to optimise the operational parameters before upscaling the process to an industrial scale. This should be done to determine the feasibility, optimum operational parameters and the cost of the process on a larger scale.

Therefore, the objective of this study is to investigate the on-site AnSBR treatment of winery wastewater at pilot-scale, using actual winery wastewater. Optimisation and validation should be done by making use of a similar central composite design as used in the laboratory-scale study.

 

4. Small winery treatment of winery wastewater

Researcher: P.J. Welz

Most small wineries in the Western Cape dispose of cellar effluent by means of irrigation to pasture. This poses a potential environmental threat, because the effluent can negatively affect soil structure and can enter the already degraded aquatic environment via groundwater and surface run-off. The wastewater should therefore, be treated before disposal. Sophisticated wastewater treatment systems require skilled labour and significant finances. There is a need to find simple, cost-effective wastewater treatment systems for use in small wineries in South Africa. Research conducted over the past seven years has identified that biological sand filters (BSF) are promising candidates.

A pilot system has been in operation at a small winery in Stellenbosch for over one year and has achieved excellent results in terms of COD removal, pH neutralisation and SAR reduction via calcite dissolution. The aim of this study is to:

  • Establish the long-term effectiveness of the systems;
  • Ascertain whether the use of a rudimentary upstream anaerobic digester would increase the efficiency of the system;
  • Determine at what stage (if ever) the sand would need to be changed.

 

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