First tests with drip irrigation promising CULTIVATION AND TECHNIQUE example, Heidemans mentions the work (labour costs) that is necessary to place the drip tube system. For the 300 hectares of potatoes grown at Scholtenszathe this year, he would have to pay 22,750 euros in wages. This is 75 euros per hectare in installation costs alone. In addition, he would need three extra workers for a period of 30 days, because that’s how long the job would take for the total surface area using current technology. And that’s not all, the tubes must also be removed again. Another problem that still needs to be solved is the length of the tubing. At this moment, the drip tubing has a maximum length of 250 metres. This is the maximum for realising even pressure distribution and output. By placing the water supply tubes in the middle of the plot, you could supply drip irrigation to plots with a maximum length of 500 metres. However, Scholtenszathe has plots with a length of 1,000 metres, in which case you need two water supply points with pumps and fertigation equipment. Not only is this expensive, it also poses practical problems, with the care of the crops, for example’, according to Heidemans. A start-up problem in 2014 due to high iron content in the source water has meanwhile been solved by linking a water filtration system to the pump. Seed potato grower Pieter Noordam also made an extra investment by setting up underground fresh water storage. Less chance of powdery scab In spite of the fact that there are still a few things that need to be adjusted, the farm manager of the crop farm sincerely hopes that he’ll find solutions for these things, because there are also positive cultivation aspects. For example, drip irrigation provides a much more even water distribution than irrigation by hydraulic guns. There were lots of storms this season, and that has led to big differences in where the irrigation drops actually fell. Moreover, Heidemans has noticed that the French-fry potatoes under the drip hardly show any infections of powdery scab any more. In the sandy / valley soils in which Fontane is grown, quality defects usually arise due to high soil temperatures and dry conditions. This is also an important quality standard, because serious powdery scab infections can sometimes lead to outright rejection of a lot. ‘Another positive aspect of drip water is that the temperature of soil and plants can be managed, not too low and not too high’, consultant Arends adds. ‘In this region, you sometimes see damage through late night frost’, she tells us. The warm irrigation water in the soil keeps the soil, plants and outside temperatures above zero.’ In the summer, an opposite effect is seen. The soil temperature doesn’t rise too much in hot weather, thus reducing the possibility of secondary tuber growth. Heidemans is also content with the extra fertiliser applications via the drip installation. ‘Last year and also this year, the crop needed some extra potash and calcium, and this can be easily added without having to drive through the crop. Another advantage is that there’s less leaching of fertiliser because you’re giving less. The minerals are applied close to the roots of the plants resulting in very little being lost. This means that hardly any fertiliser is leached into the surface water. For this reason, the water authorities are also very interested in our experiences with drip irrigation and fertigation. Many people we talk to about our tests usually first want to know what drip irrigation costs. That’s something you need to know, of course, but even more important are the yields. Look, even if it does cost 500 euros per hectare, if I earn 1,000 euros more in yield, I’m a happy man’, the entrepreneur laughs. Gert-Jan Heidemans observes that the French-fry potatoes under the drip hardly show any infections of powdery scab any more. Saved water creates fresh water storage With the same positive mindset, seed potato grower Pieter Noordam from the village of Borgsweer in the province of 32 Potato World 2016 • number 1 Pagina 31
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