Technical Bulletin: Fertilizing Wheat, Barley and Oats with Polysulphate (polyhalite)

Polysulphate is a naturally mined multi-nutrient mineral (polyhalite); composed of sulfur-based potassium, magnesium and calcium. With proven results across a variety of crops and soil types, these practical guidelines for cereal fertilization highlight Polysulphate’s flexibility and efficiency specifically for wheat, barley and oat cultivation.

Benefits

Main Benefits of Polysulphate on Wheat, Barley and Oats

• Higher yields
• Better quality of grain proteins
• Improved baking, malting and feed quality
• Increased nitrogen use efficiency

Overview

Main Features of Polysulphate Fertilizer

• Ideal sulfur fertilizer with 19.2% S and additional benefit of potassium (K), magnesium (Mg) and calcium (Ca), all in sulfate form.
• Reduced risk of sulfate loss through leaching due to 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 118 feet.
• Low chloride, very low salinity index, neutral pH, no acidifying effect.
• Natural mined mineral (polyhalite) approved for organic agriculture.
• Low carbon footprint

Functions of S, K, Mg and Ca in Cereal Crops

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

Application

Practical guidelines and application recommendations for fertilizing cereals with Polysulphate

Guidelines

• One Polysulphate application will supply all the sulfate needed by cereals.
• Polysulphate can be applied as a straight or included in a blend as part of a custom fertilizer program.
• Sulfur is needed to balance the nitrogen applied so that complete proteins can be produced. Protein content is an important aspect of grain quality.
• Polysulphate applied at 75 to 100 lbs/acre is generally adequate for most small grain yield goals, supplying all of the sulfur and calcium needed, and a large proportion of the potash and magnesium removed in the grain at harvest.
• Ensure sufficient potash is applied if straw is removed from the field.
• Polysulphate is flexible in its application timing. It can be broadcast before planting, applied at the time of planting, or top-dressed.
• Polysulphate Premium is a seed-safe source of S and K for applying with the seed.

Uptake

Nutrient uptake of wheat, barley and oats*

*Source: Fertilizer Guidlines for Montana Crops, Publication #EB 161, issued January 2023.