The decision to use compound fertilisers is usually driven by one or more of the following factors:
- Convenience
- Crop nutrient needs
- Government policy objectives
- Economics.
Convenience of using compound fertilisers
Compound fertilisers are frequently used because it is more convenient to purchase, transport, store, and apply one product than several as is the case if one chooses to use individual nutrient sources such as urea, ammonium nitrate, ammonium phosphate, and potash.
However, in many instances a single dose of a compound fertiliser will not meet the nutrient needs of the crop over the entire growing season.
Crop nutrient requirements
Compound fertilisers are often a good choice for providing a basal application of nutrients, including secondary and micronutrients, prior to or at planting time. However, because most crops benefit from higher doses of nitrogen than other nutrients, the basal dose of compound fertiliser often needs to be followed by subsequent doses of nitrogen timed to meet the nitrogen requirements of the crop.
Additionally, compound fertilisers, especially the homogeneous granulated products as opposed to dry mixed (blended) compounds, provide a means for uniformly distributing a basal dose of relatively small quantities of secondary and micronutrients in the soil without the risk of segregation, which could be detrimental to the crop if the blending process is not carried out to the required standard and / or is stored and handled in bulk.
Government policy objectives
In some cases, compound fertilisers are specified under subsidised pricing programs as a means for achieving an approximation of balanced nutrition in cases where farmer education and extension are lacking or where the cost of single-nutrient products (for example, urea, ammonium phosphate, and potash) varies widely. A wide variation in the farm-level cost of individual nutrients often leads to the excessive and unwarranted use of the least cost nutrient. Thus, the required use of compound fertilisers in a government-controlled market provides a means for avoiding such price-driven distortions in fertiliser use. The global trend toward free and competitive markets is expected to diminish the influence of government policy as it relates to the choice of a particular fertiliser product.
Economics
The simplicity of purchasing, transporting, storing, and applying a single compound product compared with several single- or double-nutrient materials clearly has economic merit. However, it is important to note that compound fertilisers, on a nutrient basis, are almost always more expensive than single-nutrient products.
Furthermore, the economics of fertiliser use must be viewed in a holistic way; not only the cost of the fertiliser but also the cost of labour, fuel, water, pest control, and, of course, the price received for the crop must be considered. Therefore, the increased cost of compound fertilisers compared with the usually less costly single- or double-nutrient products may not be of overriding significance.
Finally, compound fertilisers are uniquely suited for the fertilisation of plantation crops (for example, oil palm and rubber) and forests using aerial application techniques. Large, free-flowing granules of homogeneous compound fertiliser facilitate uniform distribution and penetration of the plantation or forest canopy. Aerial application, and therefore the increased need for homogeneous compound fertilisers, is expected to increase in the plantation sector as the cost of labour and conventional application of single nutrient materials continue to increase.
Links to related IFS Proceedings
469, (2001), Improvement of Fertiliser Efficiency – Product Processing, Positioning and Application Methods, A Shaviv.
523, (2003), Fertilisers for Protected Cropping: Products and their Development, T Kankaanpää.
769, (2015), Global Fertiliser Industry: Transitioning from Volume to Value – The 29th Francis New Memorial Lecture, A H Roy.
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