CU LTIVATION AND TECHNOLOGY Control of hormone regulation in potato plants with right knowledge and resources What Agro-Sud can provisionally conclude from the trial is that Vigor Seed can break the dormancy of certain varieties. amounts, as soon as a stress situation arises. The plant produces this in its roots’, Brans clarifies. In fact, hormones serve as messengers: ‘when there’s something wrong with the aboveground part of the plant, it’s passed on to the underground part. And vice versa’, the plant physiologist explains. An additional tool ‘When nature is in charge, the plant automatically balances any disturbed hormone regulation. But that’s not always what we, as growers, like to see or want to achieve with our food crops’, Schriever continues after the explanation by the plant physiologist. ‘Think, for example, of the abnormal formation of shoots and tubers, too slow or too fast germination and the same can happen for the development of haulm. Of course, you can already do a lot about things like the size of seed, pre-sprouting, choice of variety, plant distance, water supply and fertilisation, but in practice one or more of these factors are always missing in the crop. And if something’s wrong with this, we’ve often only tried to correct it up to now with chemistry and/or fertilisation. With this additional knowledge about plant physiology, I think we’ve acquired an additional tool. This is also reflected in the first tests we carried out this season with the various Stoller products. As Agro-Sud we have our own trial field here, which also contains areas with potatoes. There are four French-fry varieties: Marquis, Fontane, Agria, Innovator and one table potato variety: the Jelly.’ More and bigger tubers ‘First of all, we did a fertilisation test here to gain insight into the growth and development of these varieties in the trial field’, Schriever explains in the field. ‘We opted for nitrate and urea. Growth, and haulm development in particular kept pace. You could see this in the colour and that surprised us, because we’d counted on lighter foliage in the urea areas. Furthermore, the first tuber formation developed equally in both areas, but at the second setting we saw a higher number in the nitrate area, or 20 percent more tubers. The haulm also developed better in this respect. The final kilogram yield in both areas was the same, but in the urea area the 50 millimetres and over share was 14 percent bigger. What we can conclude from this when it comes to hormone regulation is the following. In the nitrate area there’s increased auxin production. As a result, haulm development and tuber initiation are the same, but the tuber filling lags behind, especially in the later French-fry varieties. In areas with urea, auxin production is lower, and therefore initiation is lower too. As a result, the plants start earlier with tuber filling. This shows that differences in the use of fertilisers can result in differences in 24 Potato World 2019 • number 1 Pagina 23

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