Seed potato grower says goodbye to inspection room CULTIVATION AND TECHNOLOGY A t 2 kilometres’ distance from the Wadden Sea, in Sint Jacobi Parochie, a village in the Dutch province of Friesland, Sijtsma grows 45 hectares of S seed from his own strains. All the activities at this farm concentrate on seed potatoes. He has stopped growing root crops in his cropping plan. In addition to seed potatoes, he now grows 90 hectares of cereals. The reason for the change is that he wants to keep the soil fertile for his strains and his S seed. Over 85 percent of the seed comes from the Hansa variety. He grows this planting stock exclusively for Peka Kroef, producer of potato specialties in Odilliapeel. Sijtsma is a Royal Warrant holder for all the S material for this company. The remainder of the seed potato acreage consists of the PCN-resistant varieties Monte Carlo, Montreal and Toronto from trading company TPC in Emmeloord. ‘I’d like to reach the stage where I grow 50 percent PCN-resistant and 50 percent non-PCNresistant varieties on my farm. The challenge is to keep the soil clean so that I’ll be able to continue to grow highly-quality seed in the future. As my son Mario is going to work with me, I want to expand to 60 hectares of seed in the coming years. That’s why we’re investing in an electronic inspection and grading machine this year’, Sijtsma explains enthusiastically. Own strain development Sijtsma expressly goes for his own strains. ‘I’m not so keen on mini tubers’, he explains. After four seasons, he delivers the material as S seed. ‘I sell all the Hansas to Kroef for a fixed price. I don’t want to say anything about that price. At any rate, it’s enough for me to be able to continue to invest in my company.’ Five years ago, Sijtsma had a store built with an ethylene storage system. ‘Storage with ethylene as a sprouting regulator increases the Hansa yield in the right size by 8 to 10 tons. We’re now harvesting more than 40 tons in the 28 to 50 mm sizes. The result of this step was that my store immediately became too small. That’s the reason why, after grading, we’re putting part of the harvest in store at Kroef’s.’ Because Sijtsma takes his task as a supplier of disease-free planting stock seriously, he opts for spraying lanes at a 45 m distance. ‘I no longer want the bother with spraying lines. Regularly driving through the fields is important in order to be able to grow disease-free seed. Fortunately, Hansa has no Erwinia problems, but is susceptible to viruses though. You can select for viruses. I already do that when the plants start forming rows. You have to be quick, and remove diseased plants as quickly as possible. Ethylene also has a positive effect here. A week before planting we start warming up the seed to approximately 19 degrees. The result is an explosion of sprouts, a fast initial development and an enormous number of stems during the growing period. Camera sees everything Sijtsma and his assistant were busy all winter grading 1,800 tons of seed. ‘Hansa is fortunate enough to have a fine yield, which means that there are many potatoes to inspect. As the business expanded, the capacity of the grading machine had become too limited. If you want to get on, you shouldn’t go back to old systems with grading sieves, but move forward. That’s why we’ve been closely following Miedema’s Smart Grader for some years now. We’ve waited with buying one until the machine was really ready’, Sijtsma explains. ‘The Smart Grader does all the work which we used to do with a grading machine and an inspection room. After 25 years in the inspection room, we now have time for other things, because the machine does it all now. We only have to import and remove the potatoes. And adjust the machine, of course. But that is simple. For if I can’t manage, the machine has an internet connection so that the people at Miedema can immediately help me grade NAK-compliant lots (General Inspection Service for Agricultural Seed and Seed Potatoes). ‘It’s my aim to be left with tubers that fall within the NAK requirements after grading. The machine can do it better than we’ve been doing in the inspection room for the past 25 years. You just know that you sometimes miss a tuber with scab, but the camera sees everything. What happens next depends on the settings’, Sijtsma explains. With this machine, we’ve everything in the right size. Important is that there are no undersized potatoes among the oversized ones’, from left to right Jos Broeders, Jack Simons and Marcel Mulder. No undersize in the oversize Sijtsma’s machine has eight outlets. One for soil, one for input and six for the various grading sizes. ‘With this machine, we’ve everything graded in the proper sizes. What’s important is that no undersized potatoes are mixed with oversized ones’, Miedema’s Jos Broeders adds. Broeders has already been working on the development of the electronic grading machine since 2004. ‘As we’re acquiring knowledge, we’ve been closely inspecting Potato World 2013 • number 2 25 Pagina 24

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