Phosta K (Potassium Sulphate/Carbonate)


  • N:0
  • P:1%
  • K:30%
  • S:8.5%
  • Ca:8%
  • Mg:2.4%
Hastings store – Product in stock.
All other stores – Currently shipping to order.
1% P, 30% K, 8.5% S, 8% Ca, 2.4% Mg
Supplied ex Hastings Warehouse or through direct shipment to any NZ port
Supplied in bulk or bulk bags
Use in: Year round
Click here for freight rates to your farm

Products FAQs

Why Use Phosta K:

Key benefits of Phosta K:

  • The Potassium forms found in Phosta K are approximately 1/3 as soluble as Potassium Chloride, resulting in a slower break down and increased Potassium utilisation and therefore production in most soils.
  • Made from 100% plant based material sourced from Sugar Cane processing by products.
  • A concentrated and cost-effective source of Potassium.
  • Contains no Chloride so suitable for Chloride sensitive crops.
  • Also contains Phosphate, Sulphate, Calcium, Magnesium and Trace Elements.

Precautions when applying Phosta K:

  • No Precautions Necessary.

Phosphate's role in crops and pastures:

Phosphorus is an essential compound of Adenosine Triphosphate (ADP), the energising component driving plant development. Phosphorus plays an important role in photosynthesis as it enables plants to store and metabolise sugars, (the energy created in photosynthesis).The physical attributes in plants that are aided by phosphorus are:

  • Larger root growth.
  • Earlier formation of plant shoots.
  • Improved stalk and stem strength in crops.
  • Improved fruit, vegetable and grain quality.
  • Promoted seed formation in crops.
  • Increased resistance to moisture and colder temperatures.

Potassiums role in crops and pastures:

  • Potassium is essential in nearly all processes required to maintain plant growth and reproduction.
  • Potassium aids plant health and helps plants resist disease.
  • Potassium enhances plant quality through size, colour, shape and vigor.

Sulphurs role in crops and pastures:

  • A structural component of protein and peptides.
  • Active in the conversion of inorganic N into protein.
  • A catalyst in chlorophyll production.
  • Promotes nodule formation in legumes.
  • A structural component of various enzymes.

When to use

Summer, Autumn, Winter, Spring

Calcium's role in crops and pastures:

  • Participates in metabolic processes of other nutrients uptake.
  • Promotes proper plant cell elongation.
  • Strengthen cell wall structure – calcium is an essential part of plant cell wall. It forms calcium pectate compounds which give stability to cell walls and bind cells together.
  • Participates in enzymatic and hormonal processes.
  • Helps in protecting the plant against heat stress – calcium improves stomata function and participates in induction of heat shock proteins.
  • Helps in protecting the plant against diseases – numerous fungi and bacteria secret enzymes which impair plant cell wall. Stronger Cell walls, induced by calcium, can avoid the invasion.
  • Affects fruit quality.
  • Has a role in the regulation of the stomata.

Magnesiums role in crops and pastures:

  • Crops and pastures require magnesium to capture the sun’s energy for growth and production through photosynthesis.
  • Magnesium acts as a phosphorus carrier in plants, and is required for better root formation and thus for better nutrient and water efficiency in plants.
  • Magnesium aids in plant respiration and the activation of many enzyme systems.


Phosta K is an organically certified form of Potassium with Potassium in Potassium Phosphate, Potassium Sulphate and Potassium Carbonate forms. Phosta K is a competitive substitute for Potassium Sulphate.