Fertilizing Potatoes with Polysulphate

Fertilizing Potatoes with Polysulphate

Main features of Polysulphate fertilizer

  • Ideal multinutrient sulphur fertilizer with 48% SO3 plus potassium (14% K2O), magnesium (6% MgO) and calcium (17% CaO), all in sulphate form.
  • Reduced risk of early season sulphate loss through leaching due to its prolonged nutrient release pattern.
  • Fully soluble, with all nutrients available for plant uptake during the growth period.
  • Excellent spreading characteristics; spreads evenly and accurately in the field up to 36 m.
  • Low chloride, very low salinity index, neutral pH, no liming effect.
  • Natural mined mineral (polyhalite) approved for organic agriculture.
  • UK produced fertilizer with a low carbon footprint.

Functions of S, K, Mg and Ca in potato crops

  • Sulphur is an essential constituent of proteins: it is required for the synthesis of three of the amino acids which make up true proteins. Necessary for high nitrogen use efficiency.
  • Potassium secures yield and quality, transport of sugars, stomatal control and is a co-factor of many enzymes. It reduces susceptibility to plant diseases and the impact of drought, and is essential for efficient use of nitrogen.
  • Magnesium is fundamental for photosynthesis, being a central part of chlorophyll molecule.
  • Calcium for strong and healthy crops; it is a major building block in cell walls and reduces susceptibility to diseases. Soluble calcium is important for skin finish.

Practical guidelines for fertilizing potatoes with Polysulphate fertilizer

  • Low-chloride Polysulphate is a sulphate-based source of water soluble potassium, magnesium and calcium, supplying all of the sulphur, magnesium and calcium needed, and a significant proportion of the potash removed at harvest, without affecting the soil pH.
  • Potatoes remove very large amounts of potassium at harvest and the proportion not supplied by Polysulphate can be applied as muriate of potash, ploughed or worked into the soil a month or two before planting. This allows unwanted chloride to move down through the soil with rainfall, and away from the roots of the potato plant.
  • 400 kg/ha Polysulphate is generally a suitable dressing for potatoes. Incorporate straight Polysulphate into the seedbed before planting, or apply it as a constituent of a fertilizer blend at planting.
  • The prolonged release characteristic of Polysulphate means that as the four macronutrients it contains are released, they provide a continuing fresh source to the growing crop.

Estimated nutrient offtakes (removal) by potatoes

Nutrient Offtakes (kg/t) Offtakes (kg/ha)
  Potato tubers 50 t/ha potato tubers
K2O 5.8 290
K 4.8 240
MgO 0.4 20
Mg 0.25 12
CaO 0.5 25
Ca 0.35 17

Guideline proportions of nutrients supplied by Polysulphate fertilizer at 400 kg/ha to a 50 t/ha potato crop

Guideline proportions of nutrients supplied by Polysulphate fertilizer at 400 kg/ha to a 50 t/ha potato crop
Sources: UK Fertiliser Manual, PDA and UNIFA

Expected benefits

  • Higher yields
  • Good skin finish
  • Improved dry matter
  • Increased nitrogen use efficiency


Fertilizing Potatoes with Polysulphate