by Robert L. Ellsworth, Ph.D.
Phosphorous (Phos) is a key element for the energy transferring system in plants and animals. After its absorption into plants as an element, it is moved into to energy capture areas of the leaves. Most of the energy capture is centered around the chlorophyll molecules. Chlorophyll is the molecular system that gives the green light refraction to the leaf. When the sunlight strikes the leaf, much of the energy therefrom is captured in the chlorophyll molecules and is quickly transferred by use of Phos to build ATP (Adenosine Tri-Phosphate). ATP is then transferred throughout the cells of the plant to release energy for respiration.
Seems simple enough, however in most Western US Soils there is an overabundance of Calcium, which creates great frustration for agronomic farmers, gardeners, and anyone else involved in plant production.
In the US, there is a fairly large source of “Raw Rock Phos” which falls within the broad category of plant unavailable mineral Phos. This material, referred to as Apatite, is Phos with several Calcium and water molecules attached. In this form, plants can only utilize the Phos after a very laborious production of acetic acid, and then only very, very slowly.
When Apatite is washed with Sulfuric Acid, the Calcium is removed and, ultimately, Phosphoric Acid is formed. Now appears the frustration. When the Phos is placed in contact with Calcium in the soil, it reacts with the Calcium and in a very short period of time will form products very closely resembling Apatite.
What is the solution to this problem? Those solutions now used are less than desirable but show some improvement over broadcast application of any raw or unprotected Phos. A test at Yuma, Arizona several years ago demonstrated that the reaction of Phos, when applied to high Calcium soil in that area, took less than two hours to reattach to at least one Calcium, forming Mono Calcium Phosphate. In this form, plants will now need to produce an acetic acid at the point of contact with the root hairs before they are able to absorb the Phos and leave the Calcium behind. This will dramatically slow uptake of the needed Phos. This study further demonstrated that in a matter of days, much of the applied Phos had even added two or three molecules of Calcium per molecule of Phos, thus reverting the supply almost to the status of the originally mined product, most of it unavailable to the plant.