ASSOCIATION OF AMERICAN PLANT FOOD CONTROL OFFICIALS (AAPFCO) OFFICIAL FERTILIZER DEFINITIONS

BENEFICIAL SUBSTANCES OR COMPOUNDS (BSC)

BSC-5 — Aluminum Sulfate

Is the aluminum salt of sulfuric acid. It is primarily used as a soil acidifier.
(Official 2013)

BSC-4 — Available Silicon (Si)

Definition deleted.
(WA 2019; Official 2019)

BSC-1 — Calcium Silicate

Is derived from naturally occurring minerals such as wollastonite or synthetically derived, having the principal formula of CaSiO₃ and is a source of calcium.
(Tentative 2016, WA; Official 2016, SA)

BSC-7 — Calcium Magnesium Silicates

Are compounds derived from fused silicates, mined materials, or synthetically manufactured materials contained in fertilizer, fertilizer materials, fertilizer blends, and/or beneficial compounds and are sources of calcium and magnesium when extracted with a validated method that includes hydrochloric acid. They may also be a source of soluble silicon.
(Tentative 2016, WA; Official 2016, SA)

BSC-6β — Hydrophobic Fulvic Acids

Are the portions of humic substances that are soluble in both alkali and acidic aqueous solutions that are separated from non-humic aqueous substances in the fulvic fraction by selective adsorption onto a nonionic macroporous acrylic ester resin of moderate polarity (i.e. DAX-8 resin, at low pH).
(Official 2015, SA)

BSC-9 — Orthosilicic Acid (OSA)

Is the monomeric form of silicon with the chemical formula Si(OH)₄ that is absorbed and transported in plants and is detected by the molybdenum blue heteropoly method.
(Official SA 2023)

BSC-2 — Potassium Silicate

Is derived from a readily soluble solid or aqueous solution having the principal formula of K₂O × SiO₂, where x = 1 to 3 on a weight basis.
(Official 2012)

BSC-3 — Sodium Silicate

Is derived from a readily soluble solid or aqueous solution having the principal formula of Na₂O × SiO₂, where x = 1 to 3.5 on a weight basis.
(Official 2012)

BSC-8 — Uncalcined Diatomaceous Earth

Contains amorphous silicon dioxide and is a natural source of soluble silicon and may contain Ca, Mg, or Fe.
(Tentative WA 2020; Official SA 2020)