Download PDF file


  • At sowing 14 December 2017
  • At harvest 27 March 2018




Potato (Solanum tuberosum)

Soil Type



Yield, and incidence of Blackleg disease

Substitution of MOP with Polysulphate increases potato yield, and also reduces the infection of potato stems with the bacteria that causes Blackleg disease.


Piedade, São Paulo, Brazil.


To evaluate the effect of Polysulphate as a replacement for MOP fertilizer and to assess the effect of calcium supply on the incidence of Blackleg disease in potato (Pectobacterium carotovorum).


The trial was done in randomized blocks, with 8 treatments. Different blends of MOP and Polysulphate were applied, each providing a rate of 320 kg/ha K2O. Treatments 7 and 8 supplied all the potassium through MOP and had part of the phosphorus supplied by simple superphosphate (SSP) with the objective of applying 50% and 100%, respectively, of the rates of Ca supplied by Polysulphate in treatments 4 (50% of Polysulphate) and 6 (100% Polysulphate).

In addition, at planting, 500 kg/ha of P2O5 was applied using MAP, and in treatments 7 and 8 the MAP rate was reduced as a function of the SSP supply. 220 kg/ha of N was also applied using urea.


  • The application of potassium significantly increased the tuber yield.
  • Tuber yield increased with partial substitution of MOP with Polysulphate, and the highest yield increase (42.7% as compared with the control and 18% as compared with 100% MOP) was achieved when 75% of MOP was replaced with Polysulphate.
  • Where 75% of MOP was replaced with Polysulphate this achieved the greatest reduction in the number of potato stems infected with the bacteria that cause Blackleg.


Results from research funded by the International Potash Institute www.ipipotash.org.