Understanding the difference between compound and blend fertilisers

As farmers navigate fertiliser purchasing decisions, it is crucial to understand the nuances between compound and blend fertilisers.

Understanding the difference between the two types of fertiliser can lead to better-informed choices, more effective nutrition and ultimately, optimised outcomes for crop performance.

This blog delves into what sets compound and blend fertilisers apart, along with their respective strengths and weaknesses.

What are compound fertilisers?

Compound fertilisers are designed to deliver a balanced mix of essential nutrients in each granule.

These fertilisers are meticulously manufactured to ensure every granule contains a precise ratio of macronutrients — such as nitrogen (N), phosphorus (P), and potassium (K) — alongside secondary nutrients like calcium (Ca), magnesium (Mg), and sulphur (S), as well as micronutrients including iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), molybdenum (Mo), and boron (B).

For example, OCI Dynamon is a compound fertiliser which combines nitrogen and sulphur into each granule for uniform nutrient distribution across all crops.

OCI Nutramon is another compound fertiliser, composed of calcium ammonium nitrate (CAN) with a 50/50 ratio of nitrate nitrogen and ammoniacal nitrogen. This formulation ensures both fast and long-lasting nitrogen availability to arable crops and grassland.

Strengths of compound fertilisers

1. Uniform nutrient distribution

The uniform nutrient composition in each compound fertiliser granule ensures consistency in nutrient application across the field.

Cereals (e.g. wheat, barley) and root crops (e.g. potatoes, carrots) in particular benefit from this uniformity, as they require a stable and consistent nutrient supply throughout their growth stages.

Uniform distribution minimises the risk of nutrient hotspots or deficiencies, promoting even plant development. This reduces the likelihood of pest and disease outbreaks linked to nutrient imbalances.

For example, balanced nitrogen application reduces the likelihood of aphid infestations in potato crops, by limiting excessive amino acid production.

Read more guidance on achieving balanced fertiliser applications

2. Convenience

Compound fertilisers simplify the fertilisation process by incorporating multiple nutrients into a single product.

This reduces the need for multiple applications and allows for more efficient use of labour and machinery.

During peak planting seasons, when time is critical, this convenience can be a significant advantage.

Reduced application frequency not only saves time but also reduces soil compaction from machinery, which can improve soil health and structure, benefitting crop growth.

Read more tips for enhancing soil health

What are blend fertilisers?

Blend fertilisers are a type of fertiliser formulation where different granules, each containing a single nutrient, are mixed together in specific ratios to meet the nutritional requirements of crops.

Unlike compound fertilisers, where each granule contains a balanced mix of nutrients, blend fertilisers maintain the individual identity of each nutrient granule.

The primary components of blend fertilisers often include:

1. Urea (CO(NH₂)₂): High in nitrogen, typically around 46% N. Urea is widely used for its high nitrogen content and cost-effectiveness.
2. Triple Superphosphate (TSP, Ca(H₂PO₄)₂): High in phosphorus, typically around 46% P₂O₅. TSP is known for its high concentration of available phosphorus.
3. Muriate of Potash (MOP, KCl): High in potassium, typically around 60% K₂O. MOP is the most commonly used potassium fertiliser.

Strengths of blend fertilisers

1. Customisation

Blend fertilisers allow for precise adjustment of nutrient ratios based on detailed soil test results and specific crop requirements.

For instance, if a soil test indicates a need for more potassium and less nitrogen, a custom blend can be formulated by increasing the proportion of muriate of potash while reducing the urea content.

However, since each granule in a blend contains a different nutrient, there is a risk of uneven nutrient distribution in the field due to variation in granule size and density. Spreader settings also need to be adjusted to account for this.

For example, urea granules (containing nitrogen) may be spread differently than triple superphosphate granules (containing phosphorus).

Uneven distribution can lead to nutrient imbalances, with some plants receiving excess nutrients while others suffer deficiencies.

This inconsistency can affect overall crop performance, potentially leading to lower yields and varying crop quality.

2. Cost-effectiveness

Blend fertilisers are often seen as cost-effective, because they involve mixing existing single-nutrient granules rather than manufacturing new compound granules.

This reduces production costs and can make blends a more economical choice.

However, this cost-effectiveness can be compromised by the issue of separation during handling.

As blend fertilisers consist of different granules, each with unique physical properties such as size, shape, and density, they are prone to segregation.

During transportation and application, heavier granules (e.g. muriate of potash) may settle at the bottom, while lighter granules (e.g. urea) may rise to the top.

This separation can lead to uneven nutrient distribution when applied to the field, which can impact crop performance and ultimately reduce the effectiveness and economic benefits of the fertiliser.

Enhancing crop productivity with fertiliser application strategy

By understanding the pros and cons of compound and blend fertilisers and considering your farm’s specific needs, you can make informed decisions that optimise nutrient management.

This involves evaluating factors such as crop type, soil condition, climate, and budget to select the most suitable fertiliser.

Always seek expert advice and base fertiliser applications on precise soil data to ensure the best outcomes for crop performance.