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Blue Bags Grow Better Crops

Grassland R&D - Blends vs Compounds

Are you suffering yield reductions from using blended fertilisers on grass?

Blended compound fertilisers are cheaper than True Granular Compounds, but an uneven spread of nutrients from a blend can lead to yield penalties of around 10-15%.

Recent spread test data on blends shows the problem:
For a blended 25.0.13 (7.5 SO3) fertiliser, the actual analysis of the fertiliser landing at each point of the bout revealed a variation in N content ranging from 25% to 21%, so that at the outer halves of the spread pattern, the N content of the fertiliser was much reduced.

 Variation in a Blend vs a True Granular Compounds FertiliserVariations in spread width of a blend vs compound fertiliser


Variation in N Application of a blend vs compound fertiliser

This means that 14% less Nitrogen than planned was being spread over half the bout width.


Why do True Granular Compounds (N,P,K,S) and blends differ in spread pattern?

Blends and True Granular Compounds differ in two ways:

1. The particles in blends are more varied in size, shape and weight, so they fly off the spreader with more variation than the particles in a True Granular Compound, leading to wide variations in nutrient spread pattern.
2. True Granular Compounds have the same chemical nutrient analysis in each granule, whilst the particles in blends have very different nutrient analyses. This means that the nutrient spread from a True Granular Compound is more even and every piece of the field gets the same nutrients.

Blending K (potash chips and S (ammonium sulphate crystals) can be a particular problem, but not for a CF Fertilisers True Granular Compound Fertiliser.



Inaccurate spreading with blends reduces grass quality as well as yield.

Grass Quality Striped Area Non-striped Area
Dry Matter (%) 17.6 17.0
Crude Protein (%) 15.7 24.2
D Value 73 80
ME (MJ/kg DM) 11.5 13.6
  • 2015 example from dairy farm
  • NK blended fertiliser
  • Applied after 1st cut silage for 2nd cut growth
  • Nitrogen in the blend did not spread evenly over the 24m bout



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