CULTIVATION AND TECHNOLOGY he explains in detail why they opted for this method earlier on, and what is needed to make it a success. Cheap production method ‘We have been cultivating S seed for an increasingly growing group of customers. These include both seed potato companies and growers. Until recently, we still worked with the 4-year stock growing of minitubers. For us, these were four years of working on the development of more and more varieties. Just imagine that, one day, things would go terribly wrong with the development of a variety, what would we do then we asked ourselves? That would not be very helpful for our customers, nor to us. The financial risk became too great. That’s why we started to look around for possibilities for a faster generation development. Growing minitubers was an alternative, but still quite expensive at that time. The main problem was the high cost price per tuber. We wondered how a land like China could produce minitubers so cheaply, which is why we also wanted to find a cheaper way of producing minitubers. In that quest, we met Timo ter Voort of Living Foods. Together with him, we developed our own hydroculture system. More tubers, lower cost price If you want to grow minitubers at the lowest possible price, you need high numbers. The more tubers, the lower the cost price. In substrate cultivation, which is used a lot in Europe, you get around 3 to 5 fully-grown tubers per plant in the 25 to 40 mm size. In hydroculture, which is what we do, you can harvest many more tubers. We pick the tubers from the root system. We start doing that from 12 to 20 mm in various picking sessions. We are able to harvest about 40 to 60 tubers per plant this way. A nice statistic: the harvest in kilograms per plant from hydroculture equals that of substrate cultivation. A minituber of 28 mm is, for example, five times as heavy as a tuber of 18 mm. You can therefore pick five times more tubers. 40 to 60 tubers per plant (photo 3) The size at which we pick the tubers sometimes depends on the variety. From the weak varieties, we pick minitubers from 15 to 20 millimetres and from the strong ones between 12 and 15 millimetres. The fact that we pick bigger tubers from the weak varieties bears no relation to the harvest potential. The smallest minituber supplies as many kilograms of end product as the biggest ones. What influences the choice of size, though, is the start of the growing process. Small tubers contain fewer initial nutrients for the start of their growth and develop a smaller root system. That’s why they need easily-absorbable extra feed after planting. That is given by applying soluble fertiliser or granule fertiliser in the ridges near the tubers with the row-fertiliser machine. So, when we talk about weak varieties, what we mean is varieties which are slow growers after planting. What is also important is not to plant minitubers for the first field generation growth too deep and preferably in finely-cultivated moist soil. This is important in order to avoid drying out and to make sure that the plants have the use of photosynthesis as soon as possible. ‘From the weak varieties, we pick minitubers from 15 to 20 millimetres and from the strong ones between 12 and 15 millimetres.’ Planting bigger fields The most important thing with minituber growing is to harvest of a lot of tubers. Thanks to the hydroculture system, we already have a great deal of planting stock at our disposal at the start of the cultivation of the first field generation. So we are able to plant out bigger plots from the very first year. Where, in the past, with the old system, we had 2 to 5 acre plots, we now have 20 to 30 acres ones. The bigger fields have the additional advantage that they can be worked with machinWhere, in the past, with the old system, we had 2 to 5 acre plots, we now have 20 to 30 acres ones. Potato World 2011 • number 3 11 Pagina 10
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