Monopotassium phosphite is an

inorganic compound In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemist ...

with the formula KH₂PO₃. A compositionally related compound has the formula H₃PO₃^.2(KH₂PO₃). Both are white solids that consist of salts of the

phosphite anion A phosphite anion or phosphite in inorganic chemistry usually refers to PO3sup>2− but includes 2PO3sup>− ( PO2(OH)sup>−). These anions are the conjugate bases of phosphorous acid (H3PO3). The corresponding salts, e.g. sodium phosphite ...

H₂PO₃⁻, the conjugate base of

phosphorous acid Phosphorous acid (or phosphonic acid (singular)) is the compound described by the formula H3PO3. This acid is diprotic (readily ionizes two protons), not triprotic as might be suggested by this formula. Phosphorous acid is an intermediate in th ...

. Phosphites of potassium are used as

fungicides Fungicides are biocidal chemical compounds or biological organisms used to kill parasitic fungi or their spores. A fungistatic inhibits their growth. Fungi can cause serious damage in agriculture, resulting in critical losses of yield, quality, ...

(in a loose sense) in agriculture to combat

water mold Oomycota forms a distinct phylogenetic lineage of fungus-like eukaryotic microorganisms, called oomycetes (). They are filamentous and heterotrophic, and can reproduce both sexually and asexually. Sexual reproduction of an oospore is the result ...

infection. Confusingly, they have also been marketed as fertilizers to avoid a regulatory burden. While perfectly capable to supply potassium to the plant, the phorphorus in phosphite form is unavailable to plants, and may even inhibit the uptake of the normal phosphate form if used in excess.

References

Phosphites Potassium compounds {{inorganic-compound-stub