Plants take in phosphate in the orthophosphate form of H2PO4 and HPO42. Traditional liquid phosphate fertilizers are 70% polyphosphate which must convert into the orthophosphate form in the soil solution. Although some polyphosphates will decompose without enzyme interaction, the primary conversion factor is enzymes produced by microorganisms and plant roots.
Orthophosphate
Each molecule contains a single atom of phosphorus. In simple terms, this looks like the individual links in a chain not being connected. In this form a plant can readily absorb the phosphorus.
Polyphosphate
Poly means “many” and refers to multiple linkages of phosphorus in each molecule. In simple terms, this would look like a chain with the links connected. Here the polyphosphate form must go through a chemical reaction converting it into the orthophosphate form to be readily available for the plant to absorb the phosphorus. There are a variety of factors that can affect the conversion of the polyphosphate to the orthophosphate form. These include soil temperature (cooler temperatures can lengthen the conversion time), soil pH, clay content of the soil, application method, along with several other factors.
Since all plants must drink their food, dry forms of phosphate fertilizer which are already in the orthophosphate form must convert into a solution in the soil before the plant can uptake the nutrient. The conversion rates of both of these processes are dependent on soil moisture and temperature conditions.
Numerous studies have shown that a lack of phosphate early in plant growth will negatively affect the yield and maximum yield cannot be achieved even if phosphate availability or additional supply is available to the plant at later growth stages.
Work by the University of Guelph has show that the phosphate supply from seed placed starter fertilizers will provide the required amount of phosphate to the plant at this critical stage in plant development. The plant is unable to source enough phosphate from the soil at this stage even in soils which test high for available phosphate. NACHURS liquid fertilizers are 80-100% orthophosphate and are specifically manufactured to be placed directly on the seed.