Water research commission

Table Grapes

Areas with hot dry summers, but sufficient irrigation sources, are the leading areas for commercial table grape production in South Africa. For this reason, the Olifants River West region is one of the major sources of table grapes in South Africa.

Heat is important for stimulating early season growth and early ripening. The hotter the climate, the earlier the harvest and this can lead to, in many cases, a higher market price. Though table grapes depend almost entirely on irrigation, increased temperatures and reduced surety of supply of water threaten to impact the grape industry.

Grapes require approximately 60 mm of water per hectare per week. Depending on soil type, table grapes should never go longer than two weeks without irrigation. The allocations of water in South Africa are a cause for conflict and concern, but it is the potential reduction in run-off that offers the largest threat to demand for irrigation (Sheridan, 2005).

Projections show that increases of minimum and maximum temperature increases of up to 3 degrees are likely by 2050. These increases will affect the degree day values of growing localities. Whereas in most parts of the world the lower limit of degree days has been the historical limitation for cultivation, it is the upper limit that is becoming pertinent for South Africa’s traditional grape growing regions. Hot weather favours sugar formation and results in sweeter grapes, which though favouring some varieties will lead to detrimental effects on the quality of others. (Johnston, 2009)

Interviews with farmers produced some interesting observations and comments:

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  Seasons seem to be getting later – shifting harvesting dates and market arrival
  
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  May monthly rainfall seems to be decreasing while June seems the same
  
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  Cold units are sufficient but decreasing and affect the dormancy period – pruning and bud-burst
  
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  Rain in summer is a big problem as it relates to insect infestations and spraying programmes
  
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  A cold spell in spring with rain can have a direct impact on yield in the summer
  
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  Snowfalls in the mountains do not seem to have been affected, though faster melting may pose a threat to dams
  
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  Winds are changing, both in strength and direction, in some localities.
  
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  Some varieties have been shifted to different slopes and locations to take better advantage of local conditions to combat warming, while some varieties are being planted to replace others
  
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  Increased temperatures will have an effect, drip irrigation will help but does not allow sprinkling for cooling for heat waves or ‘flooding’ opportunities ( i.e. more water led than normal)
  
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  Sunburn and windburn, leading to discoloration of grapes, lowers the quality and value. Shade nets are becoming more and more common.
  
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  In a scenario of water scarcity the response would be to reduce plantings – rather have less crop of good quality than same of worse quality.
  
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  Water costs are minimal in the annual budget and even a doubling of tariffs would not have significant impact (nor lead to reduction in use)
  

Table grapes are not processed as such, but are carefully picked, selected, graded and packaged before being transported to wholesalers and retailers, for export or domestic use. Table grapes are intended for fresh consumption while grapes grown for wine production, juice production, or for drying into raisins, can be processed and stored. Table grapes contain more water and usually have lower sugar content than wine grapes.

Full-time labourers are employed on table grape farms for specialist tasks such as pruning and training of trees, as well as thinning during flowering or during the first four weeks of fruit growth. Other tasks include harvesting supervision, operational duties in the pack house, irrigation management, checking for insects and diseases on seasonal basis, tractor or forklift driving and grafting.

During the harvest, Seasonal labour is employed on a contractual basis for a fixed period for picking and packing. Table 54 shows the distribution of jobs in the industry.

Table 54: Number of farm workers in the table grape industry, 2009 to 2011 (source DAFF, 2012b)

	2009		2010		2011
Region	Seasonal	Permanent	Seasonal	Permanent	Seasonal	Permanent
Berg River	13 503	2 491	13 639	2 616	13 445	2 470
Hex River	6 000	12 000	8 783	5 337	8 642	4 740
Northern Provinces	4 478	2 173	3 500	980	2 843	804
Olifants River	2 534	536	2 115	511	2 773	671
Orange River	19 918	3 452	13 750	3 350	14 802	1 943
Total	46 433	20 652	41 787	12 794	42 505	10 628

The implication of the investigations into climate change risk is that the practice of table grape growing is likely to become more risky and more expensive. The most likely effects will be shifts in management practices to accommodate an increasingly limited water supply. The changes that increased temperature and CO2 might have on quality are uncertain but the impacts on chill units and the threat of heat stress should not be overlooked. As the temperature changes do not exceed the range given by Gladstones (1992) for ideal conditions, it may be tempting to assume that quality will not be greatly affected by temperature in the next 50 years.

Responses by farmers to chill unit decreases are usually limited to dormancy breaking chemical application, which increases the costs of production. Sunburn on grapes can threaten quality and price, and the traditional response has been to introduce shade netting but the reduction of light can be detrimental.

The flow diagram below (figure 46) summarises the risk and possible responses facing growers.

Figure 46: The impacts and responses of climate change on grape production (adapted from Carter, 2006)

The implication of lower rainfall is not, per se, the biggest threat to grape growing, as the need for water is highest in the spring and summer months when the vineyards are irrigated. The supply of irrigation water is however dependent on the rainfall during the previous rainy season, often supplemented by melting snowpack. For this reason, irrigation networks have been constructed, specifically in the case of this research, in the Olifants West region, where the Clanwilliam dam and the canal system supply controlled allocations to farmers. Farmers also build holding dams where surplus allocated irrigation water can be stored.

Increased temperatures are the biggest threat to irrigation supplies. Not only is the chance of regular snowfall reduced, but even if rainfall totals do not change significantly, increased temperatures, through evaporation, reduce the amount of water available and evapotranspiration increases the water demands of the crops. Reducing evaporation from dams and irrigation canals cannot be achieved through any cost effective means, but farmers are employing different irrigation methods to avoid evaporation during watering and to provide precise amounts of water according to the plants’ demands.

Figure 47: The table grape supply chain (source OABS, 2006)

In most deciduous fruit growing, there is a requirement of a specific number of chill units². Most Grapes need about 150 chill units, compared to over 800 for apples. For this reason grapes can still thrive in very hot regions, provided the requirement is met.

Rest-breaking agents (e.g. hydrogen cyanamide) can partially mitigate the effects of insufficient chill units and can substitute for up to 300 chill units, but excessive spraying and any timing errors may damage the buds (Southwick et. al, 2003).

Of greater concern was the requirement revealed by farmers in Vredendal that the differential between the daily maximum and minimum temperature needed to be above 10°C to avoid a reduction of quality and quantity. The history of increased temperatures in the region has shown that minimum temperatures are rising faster than maxima, thus reducing the differential. Other than cooling the vine temperatures through spraying, no other adaptations have shown to be effective against this.

Figures 46 and 47 reveal how climate change can lead to increased production costs on the farm and thence to the processing and retail chain.

7.2.1 Actors in the grape value chain and their exposure to CC impacts:

1. 
   Producers
   

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  High input cost/land value ratio as a result of increases in variable costs of production resulting in greater production risks.
  
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  Increased costs of mitigating impacts of high temperatures, such as shade cloth, and drip irrigation
  
1. 
   Processors
   
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     Increased risks during packaging and transport due to increased temperatures.
     
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     Higher costs of air condition and cold chain maintenance
     
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     Market supply remains a weather/climate related variable. If the timing of the grape ripening period is altered, then the profitability of the grapes reaching the market can be affected.
     
2. 
   External input providers (non-grape raw material, transport, packaging etc.)
   
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     Risks to power supply ( and knock on risk to transport), due to increased temperature and more intense rainfall in electricity production areas
     
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     Access and availability of water leading to price increases
     
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     Increased temperatures and moisture increase demand for pesticides and thus costs
     
3. 
   Wholesalers/Retailers
   
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     Distribution risks due to transport cost and threats, and increased risk of spoilage due to increased temperatures and variable, possibly more intense, rainfall
     
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     Increased costs of raw materials leads to higher selling prices, opening up competition to export markets by other countries.
     
4. 
   Socio-economic issues
   
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     The major risk in decreasing production is the consequent reduction in seasonal and permanent labour, as table grape farming is highly labour intensive.
     
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     Any risks carried through to retailers will be reflected in the price and supply of fruit. As it is not a staple food, the risks are relatively small.
     

Thus, the most significant linkage between the impacts of climate change at the farm level to the rest of the value chain is reflected in the variable price of the raw material, i.e. grapes. When climate change causes loss of yield and/or quality in the production of table grapes, this will affect the profitability of the industry. While inputs costs promise to increase making it more expensive to farm grapes, and leading to smaller areas being planted (though increasing yields are evident) the number of individual farms is decreasing, leading to a reduction in employment numbers. This will have a knock-on effect for food security.

Quality is also an aspect which can be carried through the value chain as increased temperature leads to a higher risk of spoilage, which can be mitigated against by increased air-conditioning and shorter transport periods.

Once again, the indirect linkages of climate risk, which can be ascribed to the impacts of increased temperature and more variable rainfall, are reflected in increased costs of non-grape inputs such as electricity and transport.

3.