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Sep 30, 2009

Potato Europe shows: Fertilisation with magnesium improves potatoes’ resistance to Alternaria

For the Potato Europe show in Emmeloord, Netherlands, pot trials were used to induce deficiency symptoms for all nutrients relevant to potato growing. For N-, P-, K-, S-, B-, Mn- and Zn-deficiencies, the resulting symptoms visible in the plants were as expected. However, magnesium deficiency also consistently increased the incidence oflAlternaria.


The most common species of the Alternaria mould fungus are Alternaria solani, which may often be identified as early as July, and Alternaria alternata. After infection, potato leaves are marked by darkbrown or black spots. Solani infestation has the potential to reduce yields of late potato crops by 20 – 30 %. In 2009, high temperatures and sufficient supply of water throughout the late summer presented excellent conditions for blight. Occurrence of the disease is also connected to the particular cultivar and general stress factors. Insufficient supply of nutrients is a primary stress factor.

Magnesium plays special role among nutrients

While all nutrient deficiencies in potato pot trials resulted in corresponding deficiency symptoms without additional infection, the plant exhibiting magnesium deficiency was clearly different. This was obviously the only deficiency accompanied by a pronounced infection with Alternaria solani, as shown by the photograph below:

Translated into agricultural practice, this trial highlights the importance of sufficient magnesium supply of the crop. Application of Patentkali, combined with supplemental foliar fertilisation with 5x10 Kg ha-1 EPSO Microtop provides for an adequate mineral supply. In addition to improving yield quantity and quality, this will also reduce disease pressure from Alternaria.


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