Nutrient salts in a foliar feed

Why this page exists

A grower reading the ingredient list of a plant-nutrition product will find mono-potassium phosphate, potassium sulfate, magnesium sulfate, calcium chloride and a series of micronutrient sulfates. These are manufactured mineral salts. A reasonable question follows: how does that sit with a product range positioned around natural and low-residue inputs?

The honest answer is that plant nutrition is elemental. A plant takes up potassium as the potassium ion regardless of whether it came from a mined sulfate, a composted banana or a seaweed extract. There is no natural or synthetic version of a potassium ion. Where natural sourcing genuinely matters - pesticidal actives, residues on produce, effects on soil biology and non-target organisms - it matters a great deal. For mineral nutrients it matters much less, and claiming otherwise would be misleading.

What does differ between nutrient sources is counter-ion, solubility, salt index, pH effect and any organic fraction that comes along with it. Those are real and worth understanding.

The salts in the range

Mono-potassium phosphate · phosphorus and potassium, highly soluble, mildly acidic, low salt index. The most widely used salt in the range.

Potassium sulfate and potassium chloride - both supply potassium; the counter-ion is the decision. Sulfate adds sulfur and suits chloride-sensitive crops; chloride is cheaper but chloride-sensitive crops including many fruits, potatoes and tobacco can be damaged. Note the data issue flagged elsewhere: Potassium Pro lists potassium chloride as the active and potassium sulfate as the derived-from source. Those are not the same thing and the discrepancy matters agronomically.

Potassium nitrate · potassium plus nitrate nitrogen, in NPK Pro.

Calcium chloride · highly soluble calcium, used where calcium mobility is the limiting factor as in blossom-end rot and bitter pit. Chloride again warrants attention.

Magnesium sulfate · magnesium and sulfur, both mobile and readily taken up.

Manganese, zinc and copper sulfates, boric acid and ammonium molybdate - the micronutrient sources. Copper deserves a specific note: copper accumulates in soil and does not degrade, so repeated application over years is a genuine long-term consideration rather than a nutritional non-issue.

Phosphoric acid · phosphorus and strong acidification, useful for adjusting alkaline spray water.

A labelling issue to fix

The crop product pages carry a templated FAQ line describing each product as a naturally derived input, generated by interpolating the active field. On urea and synthetic salt formulations that produces statements such as "a naturally derived input (Urea, manganese sulfate, EDTA-Fe + citric acid)". Urea and EDTA chelates are not naturally derived. That claim needs to be scoped to the products where it is accurate - and this page is the right place to explain the distinction properly.

Reading a fertiliser label

Guaranteed analysis gives the elemental percentages. Derived-from tells you the salts, and therefore the counter-ions, the salt index and the pH behaviour. Both matter, and the second is the one most often ignored.