Solubility

POLY4 is fully soluble and delivers nutrients effectively

All fertilizers are characterised by their solubility in water at a given temperature.

The solubility of POLY4, determined in a standard test over a range of temperatures [19], is compared to the water solubility reported for common fertilizers in Figure 8.

Figure 8: Solubility of POLY4 in water (g/l) over a range of temperatures compared to other commercial fertilizers [19–24]

The water solubility of POLY4 is 27 g/l at 25°C corresponding to the amount of POLY4 that would dissolve in the plough layer of a moist, medium textured soil at a 10 t/ha application rate (Table 3).

Table 3: Summary of commercial fertilizer solubility at 25°C [19–24]

Dissolution rate characterises the transition of a solid fertilizer into a solution. Figure 9 shows POLY4 in comparison to MOP, SOP and SOP-M at 20˚C. POLY4’s dissolution rate was similar to MOP, but slightly faster than SOP during the first 15 minutes.

Since POLY4 is a mineral, dissolution results in simultaneous nutrient release. Both tests demonstrated that all nutrients are available, with near full dissolution of its nutrient content within six hours (Figure 10).

Crops benefit from this characteristic as nutrients are delivered at a pace that is more compatible with their metabolic requirements.

Figure 9: Dissolution of granular POLY4 in water over time compared to other potassium-based fertilizers [25] at concentrations of 10g/l
Figure 10: Dissolution pattern of the nutrients in POLY4 over time at 20˚ [26]

[19] ‘SGS’, France. (2013). [20] Elam, M., S. Ben-Ari, and H. Megan. (1995). The dissolution of different types of potassium fertilizers suitable for fertigation. [21] Sohnel, O., and P. Novotny. (1986). Densities of aqueous solutions of inorganic substances. Elsevier, Amsterdam. [22] “IUPAC. (2014). IUPAC-NIST Solubility Database. Available online at http://srdata.nist.gov/solubility/index.aspx [Accessed on November 2015]” [23] American Chemical Society. (2006). Reagent chemicals: specifications and procedures: American Chemical Society specifications, official from January 1, 2006. Oxford University Press. p. 242. ISBN0-8412-3945-2. [24] S. Gangolli. (1999). The Dictionary of Substances and Their Effects: C. Royal Society of Chemistry. p.71. ISBN 0-85404-813-8. [25] ‘SGS’, France. (2013) (experiment using agitation). [26] Elam, M., S. Ben-Ari, and H. Megan. (1995). The dissolution of different types of potassium fertilizers suitable for fertigation.