All of the potassium guaranteed on a fertilizer label is soluble K which implies that it goes into solution readily when applied to the soil and that it is immediately available for plant uptake. This is the sum of the total nitrogen, available phosphoric acid, and soluble potash. These are defined by the fertilizer law as the primary plant nutrients. The sum of these, the total available primary plant nutrient, makes up the grade of the mixture. The guaranteed analysis must be in whole numbers except for specialty fertilizers.
Tobacco is especially sensitive to chlorine as it reduces the burning quality of the leaf.
In addition, some vegetable crops and greenhouse flowers show toxicity symptoms and reduced quality and yields from excessive chlorine. The Guaranteed Analysis shall specify that Secondary Plant Nutrients are present in elemental form. Chelated elements shall be guaranteed separately when a chelating agent is denoted in the derivation statement below the guaranteed analysis. A Derived from statement is also required to give the sources of secondary elements contained in the mixture, such as magnesium sulfate and manganese sulfate. When a chelated form of a plant nutrient is claimed in addition to another form of the same element, the chelated portion shall be guaranteed separately.