Hunic acid is becoming a commonly added ingredient to nutrient solution formulation and nutrient supplement products with the expectation of significant positive plant response. Humic acid is not a specifically defined chemical substance, but is “a complex mixture of many different acids containing carboxyl and phenolate groups so that the mixture behaves functionally as a dibasic acid or, occasionally, as a tribasic acid” (en.wikipedia.org). The physiochemical properties of humic acid will be determined by the substance (soil, peat, coal and various dystrophic water sources) from which it has been extracted and the procedure(s) used for extraction and purification. Humic acid, being a mixture of many molecules and having both carboxylate and phenolate groups, will form complexes with ions, such as Mg2+, Ca2+, Fe2+ and Fe3+; therefore will act in much the same way as a chelate, regulating the bio-availability of these and other ions in solution. Such chelation can have both advantages and disadvantages depending on the physiochemical characteristics of rooting media and the plant nutrient ions chelated. This lack of specificity for humic acid would make its inclusion in a nutrient solution formulation and/or supplement of questionable value without careful investigation to determine its safety and efficacy. Equally important would be the identification of its source and the procedures used for extraction and purification In order to standardize humic acid products, it would be desirable to have an infrared spectrum of each hunic acid product that would identify its component structure. Such an identification of structure could then be correlated with a particular plant response when a humic acid product is added to a rooting medium.
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