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Potassium and magnesium – for optimal yield and against black spot incidence

Potassium and magnesium are important nutrients which boost tuber yield as well as quality.


Only a balanced fertilisation guarantees highest yields

On the test site Lüsche (South-Oldenburg, Germany), tuber yield could be increased by 17 percent due to a potassium sulphate fertilisation of 300 kg K2O and a simultaneous magnesium fertilisation (100 kg MgO ha-1 = 400 kg ESTA Kieserit ha-1). Compared to the pure kieserite fertilisation, a pure K fertilisation without simultaneous magnesium fertilisation on the test site’s soil, whose magnesium content was not sufficient, resulted in yield losses. Apparently magnesium was the growth-limiting factor in this alternative.


Potassium is THE nutrient against black spot incidence

In order to determine the black spot index, the tubers are put into a washer drum for 50 seconds to simulate the mechanical stress of the cleaning and storage procedure. The oxygen entering the tuber tissue causes the oxidation which results in the tuber’s discoloration. Potassium boosts the formation of organic acids whose reducing effect decreases the amount of black spots. Typically, as described in the textbook, black spot incidence decreased according to the increase of K supply. The black spot index reached a minimum at high K supply and a simultaneous low yield level which means at the point of the highest K supply per potato entity produced.


Successful with Patentkali

The test emphasises the significance of a balanced potassium and magnesium supply for potatoes. Potassium and magnesium can be applied in the potato production in form of Patentkali (30% K2O, 10% MgO and 17% fully water-soluble) in one spreading. Patentkali contains the two nutrients exactly in the same ratio (3:1) as they have been applied in the optimal fertilisation scenario on the test site Lüsche. Besides the yield increase and the quality improvement, a balanced nutrient supply helps to use the spread nitrogen more efficiently. This helps to save money and the environment.


Dr. Hans-Peter König, Kassel, Germany


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