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Fluid Journal : Spring 2014
3 The Fluid Journal Spring 2014 From The Publishers As we move through the 2014 growing season, many of your customers will want custom- manufactured fluid fertilizer blends to meet their crop and soil test needs. They will expect water-clear high quality products. To produce these formulations to meet your customer’s needs with their total satisfaction, it is important to follow select chemical principles. A fluid fertilizer with some insolubles may be agronomically suitable and functional, but not from a customer’s perception. Let’s review a few basic principles that will make your product stand out in the marketplace. Water quality. Water is the matrix/ building block for fluid fertilizer manufacturing. We know that water containing high concentrations of salt can reduce fertilizer solubility. Also, high pH can undermine the stability of secondary and micronutrients. So, make sure you use low salt, slightly acidic (pH 6.0 to 6.5) water for fluid manufacturing. Fertilizer solubility. The solubility of a fertilizer is defined as the maximal amount of a fertilizer that can be completely dissolved in a given amount of distilled water at a given temperature. Some formulators add too much fertilizer in an attempt to increase the fertilizer grade of the solution. The result is undissolved solid fertilizer salt in your fluid fertilizer. Common ion effect. Solubility is also dependent on other fertilizers in solution. If a common ion exists, the solubility of both fertilizers is reduced. For example, potassium nitrate and potassium sulfate are compatible and can be dissolved in the same solution. However, since both contain potassium, their solubility is reduced when mixed together. Fertilizer compatibility. To produce water-clear fluid fertilizers, we must blend fertilizer salts that can coexist in solution. Otherwise, a precipitation will occur. For example, do not mix sulfur or phosphate sources with soluble The Fluid Journal • Official Journal of the Fluid Fertilizer Foundation • Spring 2014 • Vol. 22, No. 2, Issue #84 calcium salts. Gypsum (calcium sulfate) or dicalcium phosphate will form and precipitate. Addition/mixing. The order of addition/mixing in fluid fertilizer formulation management to follow is: • Always fill mixing container with 50 to 75 percent of the required water if mixing dry soluble sources • Always add fluid fertilizer materials to the water before adding dry soluble materials. The additional fluid will provide some heat in case the materials are endothermic (cold). Remember, temperature influences solubility • Always put acid into water and not water into acid. • To prevent precipitation, always add acid followed by hydroxides/ carbonates and then neutral products to the water • Always add dry ingredients slowly with circulation or agitation to prevent the formation of large insoluble or slowly soluble lumps • Do not mix aqua ammonia directly with any kind of acid. The reaction is violent and immediate. Please follow these suggestions to optimize product quality and safety. We wish you great success. Dr. Easterwood is Director, Agronomic Services at Yara North America, Inc. in Tampa, Florida. Fluid formulations require following select chemical principles.