Humic Substances as Agronomic lnputs in Biological Agricultural Systems: a Review- Confusion and Non-Standardization


Humic substances have been a matter of scientific controversy for over 200 years . They are incredibly complex colloidal supermixtures that have never been separated into pure components . lnconsistent use of terminology and the previous lack of standard materials for comparison purposes have compromised the ability to translate the sparse amount of scientific knowledge to practical applications in soil environments . Traditionally, humic substances have been defined by their solubility in aqueous solution at arbitrary pH levels and molecular weights.

The use of numerous names to describe commercially available humic materials has contributed to the confusion . Humates , humic acid , Leonardite , brown coal , lignite , slack lignite , oxidized lignite , weathered lignte , humalite , fulvic acid , fulvates , ulmic acid , humic shale , carbonaceous shale , colloidal minerls , humin , concentrated humus , soil organic matter , peat , humhs acid , humus coal and dead organic matter are some of the terms that are used to describe and /or market humic substances .

Non-standardization and confusion is not limited to humic substances . For example , many labs are using soil tests that may not accurately determine soil organic matter content due to oversimplification . There are numerous tests for soil organic matter , but there is no standardized test protocol for all soils . Some of the tests for soil organic matter have to be interpreted with much caution . Additionally , conventional analyses do not predict possible adverse interactions of trace elements .

ln the past , some scientists have added to the confusion surrounding humic substances by refusing to study the materials , calling them dirt , thus putting a drag on the flow of scientific knowledge and the study of their beneficial effects on soil and plants .

The establishment of standard reference material by the lnternational Humic Substances Society has helped to remedy some of the communication problems . The society is composed of scientists from all over the world who are striving to understand the structures and functions of humic substanes . The north-central United States contact is Dr , Alan E . Olness , USDA-ARS , North Central Soil Conservation Research Laboratory , Morris .

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