Compatibility in blends and storage life

POLY4 is compatible for blending and can improve shelf life

The compatibility of POLY4 is essential since many fertilizers are sold as blends. Incompatible products often result in caking, which is affected by air humidity, particle shape and size, composition, storage duration, temperature and pressure.

Ejection pressure is an indication of the caking propensity for a fertilizer blend. Higher values are indicative of stronger, undesirable cakes that should be avoided. Table 1 provides an evaluation of the caking propensity of NPK 20:10:10 blends from a range of N, P and K sources. As shown below, changing the N source can have a substantial effect on caking propensity. Furthermore, adding POLY4 into blends as a K source shows a reduction in caking propensity.

Table 1: Caking propensity of 20:10:10 blends with different N and K sources[2]

The potential storage life of fertilizer blends can be estimated during the accelerated caking test [3]. Figure 2 shows the responses during the caking test for four blends. The time taken to reach 90psi indicates the approximate delay until a cake is formed. The results show that POLY4 has a lower propensity for caking, thus extending the overall shelf life of the blend when compared to MOP.

Table 1: Figure 2: Compression curves of 20:10:10 NPK blends made with POLY4 or MOP and different N fertilizers

Similarly, making nutrient equivalent NPK blends using different materials has an effect on storage life as shown by using MOP+urea compared to POLY4+AN+AS in 20:10:10. Table 2 shows that 20:10:10 NPK blends with POLY4 have a longer storage life than those made with MOP which is desirable for blenders and growers.

Table 2: Approximate storage life of 20:10:10 blends with different N and K sources[4]

Blending fertilizers requires consideration of all components’ compatibility to prevent caking and ensure safety. Figure 3 expands the European Fertilizer Manufacturers Association guidelines for fertilizer compatibility (EFMA, 2006) with test results of POLY4. Through accelerated caking tests, POLY4 is shown to be compatible with a range of nitrogen and phosphorus sources for blending.

Figure 3: POLY4 compatibility matrix[5-6]

No incompatibilities with POLY4 were shown amongst the products tested. POLY4 was chemically safe and only has minor caking with some fertilizers after 17 months in storage.

[2] University of Limerick. (2015). [3] Walker G.M., Holland C.R. Ahmad, M.N., Fox J.N. and Kells A.G. (1999). Granular Fertilizer Agglomeration in Accelerated Caking Tests. Ind. Eng. Chem. Res. 38. 4100–4103. [4] University of Limerick. (2015). [5] EFMA. (2006). Compatibility triangle shown with results from University of Limerick. [6] POLY4 compatibility based on caking propensity and approximate storage life from accelerated caking testing.