CULTIVATION AND TECHNOLOGY First experiences with Controlled Release Fertiliser in the cultivation of seed potatoes are promising GRADUAL GROWTH OF MINI TUBERS RESULTING IN STURDIER CROP Jan Ballast is a stock-seed and seedpotato grower in Tollebeek. The potatoes that leave his farm are therefore mainly seed potatoes in the S category. Ballast was one of the growers who was invited by Everris three years ago to start thinking about all the possibilities of a fertiliser such as Agrocote for the cultivation of seed potatoes. The gradual release of nitrogen was the argument that prompted the seed potato grower to consider whether Agrocote was suitable for his crop. The reason was that he works a lot with mini tubers. A gradual development gives the slightly more delicate mini tubers a better emergence and a stronger crop, knows the experienced stock seed grower. That is why he decided to start a small-scale trial with the Agrocote fertiliser. ‘The first year, we used it in a plot of Fontane of half to one hectare, I think. I checked the crop throughout the year and every time I thought: this isn’t what I really want. The haulm was too thin, too poor, too small. During the entire growing season, I had to stop myself using more fertiliser. Ultimately, we killed the haulm all at the same time, regular and trial crops. Subsequently, we trial lifted 2 metres of samples from a number of ridges. These samples were weighed and compared. Funnily enough, the gross kilos of regular and Agrocote potatoes appeared to be the same after all. The difference was that the lots that had been fertilised with Agrocote showed fewer oversized tubers and many more in the best-paid seed potato sizes. So, there was definitely a financial plus’, Ballast told us. Over-fertilisation no longer necessary The following year, he used the fertiliser again, but the trials failed because of torrential rain. There was over a 100 millimetres in a 24-hour period right before the moment of haulm killing. Yet, this was no reason to stop trialling. Last year, Ballast used the fertiliser in all his 1 and 2-year strains, and in the Fontane variety up to its 3rd year. This time, the stock seed grower didn’t see a poor crop, but a normal crop with not too much haulm above the ridges. ‘In fact, exactly what you want if you want to be able to select properly and to be certain that not too much nitrogen goes ‘A gradual development gives the slightly-more delicate mini tubers a better emergence and a stronger crop.’ towards the haulm but to the tubers instead. As in the first year of the trials, the harvest results showed hardly any oversized tubers and most of the tubers were in the best-paid potato sizes. If I think of the plots of seed potatoes for delivery, I could have left the plots with Agrocote to develop slightly longer than we did last season. That would have yielded a few more kilos. In which case, I certainly need the granule that releases its nitrogen over three to four months. For my strains, the two to three months’ granule is sufficient. What I like very much about this fertiliser is that I don’t have to over-fertilise anymore. And we don’t have any more problems with leaf scorching in the tops and that makes selection a lot easier. What we also notice is that the gradually-released nitrogen produces a healthy, vital and uniform crop that’s easy to select. This year, I also want to start using the fertiliser in other varieties, Première for example. I expect a particularly good result from this variety. This variety is known to grow its haulm very fast after receiving all its nitrogen at the start of the season, but at the end it collapses completely. This also applies to a mid-early variety such as Provento, of which I also develop strains’, the expert explains. Thanks to Agrocote, the seed ‘in fact, grows exactly how you want if you want to be able to select properly and to be certain that not too much nitrogen goes towards the haulm but to the tubers instead’, is stock seed grower Jan Ballast’s experience. 32 Potato World 2014 • number 3 Pagina 31
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