Grafted cucumbers provide resistance to deteriorating water quality in South Africa

Rijk Zwaan dominates the commercial cucumber seed market in South Africa, in part because of a strong relationship with producers like Stewart Colling of Somerset Farms who trials RZ varieties on an ongoing basis alongside his commercial cucumber production.

“We don’t necessarily strive to be the largest seed supplier in South Africa but we want to provide an advantage to producers, to offer solutions from the production side, to processors and supermarkets, right up to the consumer,” says Gerhard Smit of Rijk Zwaan South Africa. One such solution the company has offered to South African farmers, is its Ferro RZ cucurbit rootstock, a pumpkin rootstock on which cucumber varieties are grafted.

The Ferro RZ rootstock is Fusarium and Pythium resistant, providing pathogen tolerance and stress tolerance to water with high or fluctuating salt levels in areas with poor water quality which, unfortunately, include increasing areas of South Africa’s agricultural land.

Stewart Colling farms in Mamogalieskraal in the Northwest Province and he obtains the water for his hydroponic systems from the Hartbeespoort Dam irrigation scheme, whose water quality is notoriously high in dangerous pathogens. He used to be a cut flower producer before deciding to specialise in cucumbers around seven years ago. His cut flower background has given him a keen insight into greenhouse technology: what the essentials are, and what are the luxuries.

At Somerset Farms, cucumbers are grown in medium-tech greenhouses, a decision Colling and his partner, Jannie Fourie of Multi Plant nursery, took to maximise output within their budget, realise a quicker return on investment and to minimise dependence on Eskom, the parastatal electricity company as well as on equipment and parts that need maintenance. For instance, ventilation is done the old-fashioned way: by manually opening or closing flaps. Heating – starting when the temperature reaches 13°C – is done by two coal heat exchangers for every single greenhouse (although one single boiler can service two greenhouses in a pinch).

“Cucumbers are finicky plants to grow,” says Colling, (right in the picture), who derives real pleasure from the ‘personalities’ of the varieties he tests out. “There are the ‘lazy’ varieties, although some would say it’s not lazy, it’s risk management, because there’s not much that can go wrong with these varieties, like Boreal RZ: it’s a mule. On the other hand, Verdon RZ is a race horse. You have to ride it or it will ride you!”

“I really like Tundra RZ but other growers don’t share my feeling, I think. Two years ago we had a warm winter and the night-time temperature in the greenhouse was 15°C at which Tundra RZ did not perform as well as newer Rijk Zwaan varieties. So growers are wary of Tundra RZ. But the advantage of this variety is that you’re a week faster in production, you get around four fruits more per plant and you get even production throughout the season, no production flushes.”

“Rijk Zwaan’s new varieties are awesome,” he continues. At the moment, his winter production primarily relies on Litoral RZ and Vergel RZ and his summer production consists of Durance RZ, for its high yield, and Verdon RZ for its heat tolerance. All of his cucumbers are grafted. The trauma of the surgical procedure of grafting done on a vulnerable seedling, boosts the generative action of the plant, as opposed to the vegetative action of leaf production, which manifests in short nodes and smaller leaves at the start of the crop.

The advantage of using grafted cucumbers is neatly illustrated by the fact that he needs no chemicals for soil-borne diseases anymore. This is a huge endorsement of the rootstock (apart from a sizeable saving in chemicals) as he’s well aware of how rapidly a grower can lose all of his plants to fungal disease. As for other chemical treatments, he prefers physical pest and disease management first, since chemical foliar treatment does set a cucumber back temporarily (which is part of its finicky nature), until an economic threshold is reached.

The farm's black turf on which lettuce is grown during summer

He markets all of his cucumbers under the brand of Somerset Farms on the Johannesburg fresh produce market, between 8 000 and 12 000 boxes monthly. The South African market prefers long cucumbers, between 34cm and 36cm, and price is determined by size rather than weight.

Colling refers to the saying: “Success in the greenhouse is measured by footsteps in the greenhouse.” His footsteps are everywhere on Somerset Farms.

For more information:
Stewart Colling
Somerset Farms
Tel: +27 82 393 4608

Gerhard Smit
Rijk Zwaan South Africa
Tel: +27 76 300 7860

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