CULTIVATION AND TECHNIQUE First tests with drip irrigation promising Groningen started a drip irrigation and fertigation project last year. He also made an extra investment by setting up underground fresh water storage. This test is part of the Spaarwater project, in which DLV Plant is also participating. Together with the various Water Boards in the northern part of the Netherlands (the provinces of Groningen, Friesland and North Holland), but also the LTO funds (Agricultural and Horticultural Organisation) and Interpolis, the study focuses on the possibilities for increasing the availability of fresh water and combating salination. In addition, attention will be directed to water saving, fertilisers and crop protection products. The project is being carried out by DLV Plant, Acacia Water and Broere Irrigation. The Netafim company is the supplier of the drip tube system, among other things, Van der Meij adds. The water in the soil and in the ditches of Noordam is rather brackish. Because of its high salinity, it can’t be used for the irrigation of crops. The irrigation of seed with surface water isn’t allowed anyway because of the risk of spreading brown rot. This might be possible, though, with the method that’s being tested in Noordam. When there are no crops in the field, the drains don’t discharge the fresh water, but they collect it in order to transport it deep underground via a collecting drain and pipes to saline spots 10 to 30 metres underground. The fresh rain water pushes the saline water away thus producing a big storage basin of irrigation water. Before the rain water can sink into the soil it is first filtered. The system is designed so that the water is naturally filtered in the soil. ‘This process is expected to kill harmful bacteria such as Erwinia and Brown rot’, project leader Jouke Velstra of Acacia Water says. ‘As scientific evidence is also necessary, the NVWA (Netherlands Food & Consumer Product Safety Authority) is also involved in the project’, Noordam adds. Drip tubes below the plough pan. Storage underground makes the water oxygen-poor.’ We didn’t immediately notice that at first. We pumped the water straight into the drip irrigation system, but we know now that this stopped the plants from growing. The oxygen-shortage problem could easily be solved by first having the pumped-up water cascade from a specific height into a container, because the water takes in oxygen from the air during the drop’, says Noordam. Another feature of the drip irrigation test with seed potato growers is that the drip tubes are 40 centimetres below ground level, so below the plough pan. The advantage is that you don’t need to hoist tubing around after harvesting. It’s quite a bit more expensive to install, of course.’ Noordam, who grows approx. 50 hectares of seed potatoes annually, has made 1.5 hectares available for irrigation tests near his own farm yard. The plot has been divided into 3 sections in order to grow potatoes in a 1:3 cropping plan. ‘We’re growing the Spunta variety in this test. We’re now in the second year of the test. Due to start-up problems in the first year, we don’t have any harvesting results yet. The first results are expected after the coming harvest’, says On Jos van Sambeeck’s land around Reusel in 2014, the yield and the quality were significantly better with drip irrigation than with traditionally-irrigated potatoes. Noordam. What he can say is that he’s seen that the irrigation water is a welcome supplement in dry periods because it keeps the plants growing. ‘The availability of water during initiation is especially important’, he knows from experience. This gives more tubers, a more even grading and less chance of scab. During this dryer period, the drip irrigation is switched on every other day. A day of ‘rest’ in between is necessary to avoid spoiling the structure of the heavy sandyloam soil. For the same reason, the irrigation stops every now and then during the days when it’s on. What Noordam likes about the drip irrigation is that you can add fertiliser to the Potato World 2016 • number 1 33 Pagina 32
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