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Institut für Pflanzenernährung

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    Müssen Johannisbeeren chloridfrei gedüngt werden? : Studien zur Aufnahme und Verlagerung von Chlorid durch verschiedene Johannisbeerarten
    (2009) Blank, Otto-Heinrich; Römheld, Volker
    Is there a need for the use of chloride-free mineral fertilizers for currant as a common berry fruit? It is a well-known practice to apply chloride-free potassium fertilizers for berry fruits since decades. Such a chloride-free fertilization with mineral fertilizers and in particular with potassium fertilizers as K2SO4 or potash magnesia (Patentkali) is also recommended in most standard text books for plant nutrition and fruit production. The aims of the present Ph.D. thesis were (1) to find out by inquiries of literature the scientific background of such a statement for a chloride-free fertilization of berry fruits as currants and strawberries (Chapter 2). Further, (2) the extent of the possible different susceptibility to chloride toxicity of various cultivars of currants and of strawberry should got evaluated by different experimental approaches (Chapter 4). In detail short-term uptake studies in nutrient solution (Chapter 6 and 7), but also pot (Chapter 8) and field experiments (Chapter 9 und 10) mainly with different cultivars of currants (black, red and white currants) but also with strawberry were conducted. Besides uptake and translocation of chloride into shoots and berries also sodium has been studied because chloride and sodium are closely linked in application of high chloride containing potassium fertilizers such as potassium chloride (muriate of potash) or kainite as a low-grade K fertilizer (Chapter 6 ? 9). In addition the possible leaching of chloride by application in autumn during the following winter months as a possible strategy to minimize chloride toxicity in currants and strawberries was evaluated in the field experiments (Chapter 9 und 10) as well as in a model experiment with soil filled columns under field conditions (Chapter 11). All these different approaches should finally allow giving a clear recommendation whether a chloride-free fertilization of berry fruits (currant and strawberry) is further needed or an application of chloride-containing potassium chloride (muriate of potash) can be used in berry fruit production by farmers in future. The inquiries of literature did not give any scientifically reasonable answer for the often cited differences in susceptibility of berry fruits or of various groups of currants (black, red or white cultivars) to chloride (Chapter 2). The nutrient solution experiments revealed the various possible mechanisms involved in the pretended different susceptibility to chloride (Chapter 6 and 7). It got obvious that black cultivars of currants had a lower uptake rate of roots for chloride than both other groups, the white and red currants (exclusion of chloride by roots). However, this exclusion of roots had only a limited capacity with only a marginal effect on chloride accumulation in the shoot in the long-term field experiments. The second possible mechanism, storage of chloride in roots (retention) as described for different cultivars of grape vine could not be observed for black currants. This missing difference in the relative translocation of chloride from roots to shoots was in contrast to sodium. Both black cultivars had a much lower sodium translocation to the shoot than red and white cultivars due to a high accumulation (retention) of sodium in roots. These various mechanisms for the described differences in susceptibility to chloride and sodium including possible differences in tissue tolerance were further studied within a pot (Chapter 8) and two field experiments (Chapter 9 and 10). All three experiments demonstrated with the determined critical chloride toxicity concentration in leaves (tissue tolerance) in accordance that currants are quite sensitive to chloride without differences between black, red and white cultivars. Crossing this critical value of about 10-15 mg Cl/g leaf dry weight necrotic symptoms on the edge of leaves could be found independent of cultivars. However such necrotic symptoms on leaves could be only found at a ?Worst-Case-Scenario? with an excessive (2 times) potassium application as the low grade K fertilizer kainite and in the pot experiment without the possibility of leach out of chloride (Chapter 8). In both field experiments with a praxis-relevant potassium application rate and the potential of chloride leaching during the winter period no such symptoms of toxicity could be observed with currants (Chapter 9) and strawberry (Chapter 10), even at a ?Worst-Case-Scenario? with the use of kainite at begin of the season. An adequate leaching of chloride in deeper soil layers during the winter could be proved by analysis of chloride in different soil horizons, but also by leaf analysis of currants and strawberries. Therefore all these above-mentioned results do not support the claim for a chloride-free potassium fertilization of berry fruits such as currant and strawberry.