South African kiwi fruit growers can lift yields by following best management practices, as well as by exploring new high-yielding gold varieties. Robyn Joubert reports.
The South African kiwi fruit industry is relatively small, with an estimated 200ha of the green-fleshed varieties under production. The industry has only about 10 growers, who produce 2 000t/year. However, green kiwi fruit yields generally fall short of its genetic potential.
“Production in South Africa has not kept pace with current best practice methods. While New Zealand and Australian growers are achieving yields of 40t/ha, South African yields are poor at 12t/ha to 15t/ha,” says Colin Lye, MD of Australian plant breeding variety management company Global Plant IP. He visited SA in June to look at production sites and meet with potential growers.
Yet through training and following best management practices, these yields can increase. One of the key methods is cane replacement, or the removal of previously cropped wood, which is commonly practised in the table grape industry. “Growers should follow an annual self-replacement fruiting system. Each year you are producing two crops: growing,
new wood for the following year and thinning out old wood from the previous year. This is much the same procedure that is followed for canes on a table grape vine. However, almost none of the existing kiwi fruit orchards in SA are produced in table grape areas so growers do not have this knowledge,” says Colin.
The woody, twining vines of kiwi fruit are grown in sunny areas protected from strong winds by netting.
“The vine wants free-draining soil, much the same as avocado and citrus. It can take a lot of rainfall but it can’t sit in water as it is sensitive to phytophthora root rot ,” Colin says. To prevent water from pooling by the vines, irrigation sets should be shorter and more frequent, and sprinklers should be positioned away from the base of the vines. Irrigation management has a further yield benefit: “We tend to use irrigation throughout the year, even in summer rainfall areas, because bud break is earlier in August so there is a risk of late frost. The best way to manage frost is by watering with the sprinkler system.
Typically, the water source is higher in temperature so when applied at the onset of a potential frost period, it keeps the air temperature raised until the sun re-emerges,” says Colin. Netting is another important management tool. It is used not only for hail protection but also for wind management. “Growers can increase their fruit pack-out percentage by putting netting over the crop, either permanently or during high risk periods. Up to 90% of fruit picked should be first-class grade but if netting is not used, growers are likely to get only 65% first-class fruit. Growers are paid on final trays packed and exported so it is crucial to optimise both yields and fruit quality,” says Colin.
Compost, manure or silage should be used as a soil conditioner, Colin advises. “When developing a new orchard, we suggest growers start by introducing high levels of a suitable compost and/or animal manure. It slows down weed competition, improves organic matter and water filtration. The vines in new orchards are pretty hungry for nitrogen, potassium and phosphorus and the soil pH might need correcting and maintenance. The sweet spot is pH 6,2.”
The most serious kiwi fruit diseases are Botrytis rot, which can be a major disease after rain when flowering, and Psa, a bacterial disease caused by Pseudomonas syringae pv. actinidiae. Psa has caused severe economic losses for growers in countries such as New Zealand, Italy and Japan. “However, Psa is not yet present in SA. As long as the grower starts with Psa-free material and maintains a stress-free environment, the risk of getting Psa is pretty low.
“Phytophthora root rot is one of the more serious diseases which can seriously damage and even kill vines if not managed properly. “Good hygiene practices should also be followed, which includes limiting visitors to the orchard and using your own pruning equipment which does not leave the farm. South African kiwi fruit farms are not intensely concentrated so if Psa turns up it can be isolated.”
Experimenting with new kiwi fruit varieties also has the potential to lift yields. Global Plant IP released a series of seven gold flesh cultivars (Z487, X60, Y368, Y118, W45, W47 and S600) in 2008. “Gold yields are higher than green at more than 70t/ha compared to 40t/ha for green kiwis,” says Colin. Apart from yield, the gold variety offers many other advantages over the green variety. “We have made a major advancement in taste: they are about six brix sweeter than green varieties. They are also supermarket-ready five to seven days from harvest and can fetch prices three times higher than green,” said Colin.
Cane replacement, or the removal of old woody vines, must be done annually.
To hold up prices of gold kiwi fruit, Global Plant IP is restricting plantations. “So far, 800ha gold has been planted: in Australia, New Zealand, North Africa, Europe, South America and Turkey. In SA, a maximum of 250ha will be grown, which will utilise 15 to 18 growers.” In SA, Global Plant IP’s gold plant material is supplied by Stargrow, a Cape-based nursery which introduces new crops under managed programmes. It will be the local arm for the development of the new orchards and also will manage Global Plant IP’s 3,5% royalties on the fruit.
The gold-fleshed kiwi requires far less chilling units than the green variety and is suited to early low chill zones in the KZN Midlands such as Eston, Richmond and Mid Illovo, and in Limpopo. A trial has also been started in Sunday’s River. The Western Cape is potentially too windy and the fruit would clash with fruit from New Zealand and/or Chile, although a trial in the Cape is underway.
Establishment costs are high at about R350 000/ ha to R450 000/ha to set up for the pergola system, involving 1 000 plants/ha, posts, wire, irrigation, frost control and netting if hail and/or wind is an issue. However, if a grower has a pre-existing table grape orchard, the outlay can be reduced to between R150 000/ha and R200 000/ ha. Kiwi fruit harvesting is labour intensive, requiring one labour unit per hectare or 2 000 labour hours per hectare per year.
“Growers should be able to finance 10ha or more,” says Colin. “The genetic potential is 70t/ ha although if growers can achieve 40t/ha (which currently has a farm-gate price of roughly R20/kg), there is a good chance the capital outlay can be recovered after four years. It dovetails well with crops such as avocado, mango, litchi, citrus and table grapes, as they use the same packing lines and equipment. This means the grower gets a better return of those overheads.”
Kiwi is a high risk crop due to limited local knowledge. Failure to establish the crop can be an expensive business. However, the risk is negated by gaps in market supply and genetic advances. “Virtually the entire SA crop will be exported to fill an eight- to 12-week window period from February to April. It is this gap, along with advances in genetics, that will see growers extract the three P’s: production, price and profit,” says Colin.
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