‘Ethylene in seed provides higher yields and easier work’ CULTIVATION AND TECHNOLOGY HOW DOES ETHYLENE WORK? Ethylene (C2H4) is an ageing hormone that plants produce themselves. The volatile substance is responsible, for example, for the faster ripening of a banana in a fruit bowl if you put an apple next to it. Even a bunch of flowers close to a bowl of ripe fruit will speed up the wilting of the flowers. In a potato, ethylene breaks through the dormancy and starts cell division. At the same time, it slows down the cell stretching, as a result of which the sprouts stop growing longer while they are exposed to the hormone. After some time, short, sturdy sprouts appear as well. Because the top sprout dominance is disrupted, there will be more runners and the plant will also produce more stems. In the storehouse, ethylene is produced from ethanol; ethanol is converted into ethylene and water with a special accumulator. This needs to be a continuous process. Because it is volatile, it reaches everywhere but it also escapes easily. ments for my own seed so that you can have two different temperature regimes. Field crop Because ethylene is such a volatile gas, it can easily reach all the tubers. The ventilators are not needed to distribute the gas through the lot. That’s also the reason why ethylene can be used for field crops. Gebbink is taking advantage of that: ‘I prefer to leave my first and second-year strains well alone. They’re often still in ethylene in March. Only then will we inspect them. And, if necessary, they just go back for a bit longer.’ There were no further problems during storage. It’s important, though, to keep on monitoring the temperature and the CO2 values. A too high CO2 concentration unsettles the tuber, is Ten Brinke’s experience. Gebbink couldn’t do without the additional cooling, but there are also growers who use ethylene in combination with pure outside air. Hartveld of Ten Brinke: ‘We have very good results in well-insulated storage places. If the temperature fluctuates too much, there’s a chance that you’ll also have to rotate them a few times. And that‘s what you want to avoid. As far as CO2 is concerned, we start with a limit value of 5,000 ppm. If it exceeds that value, we start refreshing the air.’ The ethylene accumulator can be operated through the shutters; when the shutters are opened, the accumulator will be automatically stopped. To keep things going There isn’t a real blueprint yet for the application, it turned out on the field day for growers. Experiences correspond for the most part, but every grower has his own priorities. Gebbink: ‘There are so many factors that influence the result: how long are they stored, what is the temperature, what were the conditions when they came in? All these aspects vary from year to year. We’re learning to take all these things into consideration. But for me, there’s no doubt that most varieties do well with ethylene. The best example is the Fontane variety. If you don’t treat that variety, you’re losing out. We’re harvesting 20 percent more tubers.’ Gebbink thinks that ethylene may increase his yield per hectare even further. He prefers that to buying more land. The trick is, however, to get a better return from those extra tubers. Because even without that extra yield, it was quite a job this year to keep the crop going until the very end. At any rate, Gebbink still has a few strains in leaf at the end of July. Most varieties react to ethylene with a larger number of tubers and more even sizes. In these Fontanes, the result is extremely good. Object left: from the cool-storage twice rotated, right: ethylene storage. The number of tubers per linear metre is 65 and 82 respectively. When seed is sold per tuber in future, Gebbink foresees the fast acceptance of ethylene technology. ‘At this moment, growers may still hesitate because of the costs. The total investment of 200 euros per ha (see box) is quite a lot. But this is well and truly earned back in most varieties. ● Egbert Jonkheer Potato World 2014 • number 4 23 Pagina 22
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