CULTIVATION AND TECHNIQUE First tests with drip irrigation promising water. ‘I sometimes apply foliar fertiliser, and I can now apply this via the tubes, and don’t have to go around the field with the tractor and spray. All in all, he reckons that a lot still needs to be done to lower the costs of the entire system with simpler techniques. At the moment, pumps, filters and fertiliser are still too complicated and expensive because they come from other application types, but that’s what these tests are for: to find out what works and what doesn’t. For example, I use the fresh water from the basin not only for irrigation, but also for crop spraying. I used to get that from the tap’, Noordam explains. ‘We’re going to continue the test for the next three years, just to figure out how to lower the costs of the system. We also want to work out how to improve the use of water and fertiliser’, says Velstra. Higher yield and better grading at Van Sambeeck While Noordam still has to wait a few years for results; crop farmer Jos van Sambeeck, from Reusel, knows a lot more after three years of practical experience. This is demonstrated by the DLV Plant report over the 2014 cropping year drawn up by former DLV Plant extension officer Geert-Jan van Roessel, who recently started work as an agronomist at Lamb Weston / Meijer, the potato processor in Kruiningen. Van Sambeeck also grows French-fry potatoes for Lamb Weston / Meijer and has installed drip irrigation in his bed cultivation. In the middle of these beds lies a channel which holds the drip tubing. This means the potatoes receive the water from higher up. Around Reusel, the soil is predominantly sand with an organic substance content of approx. 5 percent. In 2014, there was no difference in growth between the plots with drip irrigation and those with conventional irrigation. However, 3 percent less water was used in drip irrigation during a season which also had sufficient natural rainfall. The saving is expected to be much bigger this year. In the same token, the plots with drip irrigation used less fertiliser than those with the traditional irrigation. The difference is some tens of kilograms of the various minerals per hectare. Whether this saving will be achieved every year is hard to say as yet. Interesting, of course, are the yield and quality measurements of the current year. Both the yield and the quality were significantly better with drip irrigation than the traditionally-irrigated potatoes. The yield was 1,742 kilograms higher per hectare. The grading was also much bigger with 92 instead of 42 percent being upwards of 50 millimetres. The underwater weight was 422 grams compared to 390 grams on the conventionally-irrigated plots. All in all, a plus of 417.14 euros. Still a lot to do From all the trials so far, the outcome is positive if we look at cultivation and yield improvements. It reduces the chance of frost damage, there’s less risk of infection with diseases such as scab, it increases the number of tubers, and improves the grading and the underwater weight. Researchers/advisors and growers also consider drip irrigation as an insurance premium for dry growing periods. A year like this one, with an enorThe installation of tubes for drip irrigation is more the task of the contractor is the view up to now of growers on the bigger potato farms. mous rain shortage in many places during the months of June and July, makes many people curious about the yield differences that will be revealed later. There’s still a lot to do as far as improving the technology is concerned. The equipment usually comes from greenhouse farming and needs adjusting for open cultivation. The main thing is that it should be cheaper and simpler, is what both researchers and growers who are trialling drip irrigation say. Van Sambeeck, for example, thinks that the installation of drip irrigation is more a task for contractors, Van Roessel writes in the report. ‘As a grower, you don’t have labour available in such a short period.’ The tubes need to be placed over a larger working width to limit the number of tracks in the field. In his view, the smaller plots are better suited for drip irrigation than the very big ones. This view also gets the support of growers such Heidemans and Dijkstra. On the sandy soils, there are still a few problems to overcome such as the high iron content in the groundwater, and on the silty clay soils improving the fresh water storage is still an issue. One thing is certain, after visiting and studying all these projects: to be continued. ● Leo Hanse Potato World 2016 • number 1 35 Pagina 34
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