Technical Bulletin: Fertilizing Peanut with Polysulphate (polyhalite)

Polysulphate

Polysulphate® as a fertilizer source

Granular Polysulphate® is a natural mineral from underneath the North Sea that contains four nutrients: sulfur (19.2%), potassium (14% K2O), magnesium (3.6%), and calcium (12.2%). It is a single complex crystal that is mined, crushed, and ready for use in agricultural fields. ICL sells this multi-nutrient mineral (polyhalite) as Polysulphate. It is OMRI certified, low in chloride and crop safe, and suitable for use alone or in blends and compound fertilizers.

Why is Polysulphate recommended for peanuts?

Peanuts, being deep-rooted legumes, naturally capture nitrogen and excel at gathering essential nutrients like phosphorus (P) and potassium (K). Yet, to enhance peanut yield, it’s crucial for farmers to focus on maintaining the soil pH, preventing zinc toxicity, addressing manganese deficiency, and ensuring ample calcium for the crop. Polysulphate, a slow-release fertilizer packed with sulfur (S), potassium (K), magnesium (Mg), and calcium (Ca), has proven its effectiveness in research trials conducted in Georgia.

Polysulphate demonstrates comparable performance to gypsum, offering a dependable and economically viable approach to maximizing peanut yield. Furthermore, using Polysulphate instead of gypsum can lead to significant cost savings due to differences in application rates.

Features of Polysulphate fertilizer

1. Slow-release mineral fertilizer that has the capability to provide a sufficient and continuous supply of S to satisfy all the needs of the growing peanut crop
2. Natural multi-nutrient mineral with every granule composed of sulfur-based potassium, magnesium and calcium that is low chloride, very low salt index, neutral pH, no acidifying effect and safe to apply
3. Excellent spread and blendability when applied via broadcast, precision application when used in a band, and superb blendability with other common fertilizers
4. Flexible application that can be applied as a pre-plant or at planting with proven results across a variety of crops and soil types
5. Natural mined mineral (polyhalite) approved for organic agriculture that helps to improve nutrient efficiency, soil structure, root development, water infiltration, and seed emergence

Gradual Sulfur and Potassium Release to Meet Peak Demand

Source: University of Nottingham, UK, 2016.

Nutrient Function

S, K, Mg, and Ca in Peanut

• Sulfur (S) is an essential constituent of proteins: it is required for the synthesis of three of the amino acids which make up true proteins.
• Potassium (K) secures 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 (Mg) is fundamental for photosynthesis, being a central part of chlorophyll molecule, and is important for carbohydrate transport to sink organs.
• Calcium (Ca) for strong and healthy crops; it is a major building block in cell walls and reduces susceptibility to diseases.

Peanut Nutrient Uptake and Removal

Nutrient removal coefficient derived from Alabama Extension: ANR-0449 (2023). Nutrient removal values are expected to vary by geographic location and growing condition. These numbers should be use as a guide. Use locally available data whenever possible.

Guidelines

Practical guidelines for fertilizing peanut with Polysulphate

• Single Polysulphate application at pre-plant or planting is enough to fulfill all your peanut crop’s sulfur requirements.
• Polysulphate can be applied alone or in a blend as part of a fertilizer program to meet the needs of your peanuts in terms of sulfur (S), calcium (Ca), potassium (K), and magnesium (Mg).
• To meet the nutritional needs of your crop, apply 200 lbs./A of Polysulphate. This will provide the Ca needed along with S, K, and Mg.
• It’s worth noting that for seed peanuts, it may be required to apply additional Ca during early bloom for optimal results. Also, if your soil tests reveal at least 1000 ppm of Ca in the top 4 inches and K and Mg levels exceeding 100 ppm, Polysulphate applied at 200 lbs./A alone can sufficiently provide Ca, K, and Mg for your peanut crop.

Nutrients supplied by Polysulphate at the recommended rate* (200 lbs/A) to peanut for a yield goal of 4000 lbs./A

*Recommendation is based on nutrient removal and should be adjusted based on soil test. These recommendation numbers are guidelines or starting point.

Trials

In all multi-location trials Polysulphate produced similar yields to a high amount of gypsum on peanuts with greater economic returns based on the application rates.

MULTI-LOCATION PEANUT TRIAL 2020

Polysulphate produced similar yields to a high amount of gypsum on peanuts with greater economic returns based on the application rates.

• Four replications of each treatment.
• Gypsum was applied at 1000 lbs./A at early bloom
• Polysulphate was applied at 100 lbs./A at planting.
• Dryland and irrigated production systems

MULTI-LOCATION PEANUT TRIAL 2021

Polysulphate produced similar yields to a high amount of gypsum on peanuts with greater economic returns based on the application rates.

• Four replications of each treatment.
• Gypsum was applied at 1000 lbs./A at early bloom
• Polysulphate was applied at 100 lbs./A at planting.
• Dryland and irrigated production systems

MULTI-LOCATION PEANUT TRIAL 2022

Polysulphate produced similar yields to a high amount of gypsum on peanuts with greater economic returns based on the application rates.

• Four replications of each treatment.
• Gypsum was applied at 1000 lbs./A at early bloom
• Polysulphate was applied at 100 and 200 lbs./A at planting.
• Dryland and irrigated production systems

Polysulphate Benefit Highlights

• Achieve higher yield & quality
• Increase nitrogen use efficiency
• Improve soil health as it helps to maintain soil structure for air and water movement
• Provide peanuts with gradual release of sulfur-based, plant-available S, K, Mg and Ca
• Achieve cost savings compared to gypsum (based on application rates in trials above)