Tom Sharp, CCA, Lewiston, UT
There has been a lot of interest in organic acids and their use in agriculture during recent years. These organic acids are derived from ancient deposits of organic matter that have had millions of years to decompose. The organic matter is decomposed much more than the humus that is so desirable in our soils. This dark brown to black product is often found near coal deposits in the earths crust and originated as peat, brown coal, soil, or leonardite. At the molecular level it is an extremely large and complex molecule with no specifically identifiable structure. Organic acids can be broken down into three different parts: humic, fulvic, and humin.
Humic acid is the most commonly available form of organic acid and contains humic, fulvic and humin fractions. This is usually the raw product that has been mined, crushed and screened for proper size. The name humic “acid” is actually a misnomer because it has pH of 11 or higher. Most lawn and garden professionals will refer to humic acid as “humate”. It comes in a dry granular form as well as liquid. Dry humic can be added to most dry fertilizer blends at a rate of 20 – 40 pounds per acre. When blended with dry phosphate fertilizer, humic attracts microbes to the prills and enhances degradation of the waxy protective coating. This speeds up the rate at which the nutrients become available for plant use. Humic also acts like a chelating agent to protect phosphate from being tied up in the soil. This happens because humic has an enormous number of binding sites where nutrients can attach themselves and are protected until needed by a plant.
Liquid humic is commonly added to liquid nitrogen (UAN 32) or to liquid phosphate (10-34-0). UAN 32 is a very popular fertilizer used to top-dress winter wheat in northern Utah and Southern Idaho. The addition of humic to the fertilizer will minimize burning of the leaves and reduce the amount of nitrogen that can volatilize. It is not uncommon to use over 80 available units of nitrogen with the addition of humic on irrigated winter wheat. This is normally done as early as possible in the spring and usually in conjunction with an herbicide application using a ground rig.
Fulvic acid is truly acidic, having a pH below 7 and is relatively easy to extract from the raw humic. It is usually a clear to amber colored liquid and the actual percent fulvic can vary between manufacturers. Several herbicides and foliar nutrients respond well to additions of fulvic to the spray tank. Fulvic is normally very active in the plant and the soil but is only a small percentage of the overall humic.
Humins are the most difficult to extract but are the most stable in the soil and provide more direct plant activity than fulvic. Since they are so difficult to extract, the best way to apply humin to the soil is by using the full humic acid in its raw form.
Organic acids benefit the soil by increasing the water holding capacity, adding stable organic matter to the soil, and increasing the nutrient holding capacity. When added directly to the nutrients being applied, organic acids increase efficiency and protect the environment. In extensive research done by the University of Idaho, organic acids were shown to provide an economic return to growers in almost every trial.
