European Fertiliser Blenders Association
It is often assumed that the nutrient analysis of complex compounds is more accurate than that of blended compounds. By definition, complex compounds are chemically homogenous, and the nutrient content of each individual granule is therefore the same.
Blends are formulated using granules with different nutrients contents or different proportions of the same nutrients, so are less homogenous in terms of chemical composition and nutrient analysis within the between individual granules.
This assumption is probably valid in the case of poor-quality blends made with a wide range of different size particles between the various raw materials used in the formulation.
Blends made following the guidance in the EFBA handbook formulated with raw materials with similar size particles do not segregate and will be highly accurate in terms of nutrient analysis throughout the product.
Nutrient analyses of 86 samples of high-quality blends produced in the UK following the EFBA handbook were compared with 46 samples of complex compounds. Sampling was undertaken by trading standards officers between 2016 and 2021 using the methodology as prescribed in Annex IV (A) of EC Regulation 2003/2003 (EC 2003). Analyses were conducted by independent laboratories operating on a ‘blind’ basis, using the methodology laid out in Annex IV (B) of EC 2003.
All samples were taken from products in 600kg IBCs.
The table below shows that the nutrient content of high-quality blends is as consistently accurate as that of complex compounds.
The overall deviation between the declared and measured analyses for N, P and K combined was 52% less in the case of the high-quality blends (+0.66%) compared to the complex compounds (+1.38%).
At the point of sampling, the blends had been produced and bagged, loaded on to a vessel, shipped, off-loaded and stored dockside giving ample opportunity for segregation of nutrients to have occurred.
| Product Type and Sample Numbers (n) | Declared NPK | Analysed NPK | Deviation Between Declared and Analysed | Total NPK Deviation | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
| N | P2O5 | K2O | N | P2O5 | K2O | N | P2O5 | K2O | ||
| Blends (as per EFBA Handbook) n=86 | 21.87 | 8.03 | 9.48 | 22.03 | 8.40 | 9.61 | +0.16 | +0.37 | +0.13 | +0.66 |
| Complex Compounds n=46 | 20.59 | 9.82 | 9.85 | 20.45 | 10.67 | 10.52 | –0.14 | +0.85 | +0.67 | +1.38 |
A ‘high-quality’ NPK 20-10-10 blend, made with 59.58% granular CAN, 21.75% DAP and 16.67% MOP, plus 2% of limestone grit, were compared to a ‘poor-quality’ NPK 20-10-10 made with 46.62% prilled AN, 21.75% DAP and 16.67% MOP, plus 14.96% of limestone grit.
Each product was spreader tested under controlled conditions through precisely calibrated spreading equipment a spreader manufacturers test hall.
Fertiliser was collected from trays at 1.0m intervals across the spread width and independently analysed in accordance with The Fertilisers (Sampling and Analysis) Regulations 1996 (SI No 1342) (GB 1996).
The distribution of each nutrient expressed as a percentage of weight is shown in the below graphs.
With the blend made in accordance with the EFBA handbook, there was an even distribution of all three nutrients across the spread width with the 20-10-10 maintained to both left and right sides of the spreader.
With the blend not made in accordance with the EFBA handbook, there was significant nutrient segregation of all three nutrients across the full spread width. The nitrogen level was slightly above 20% just to the side of the spreader, but decreased to 10.64% at 13m on the left-hand side and 7.23% at 16m on the right-hand side.