Soil Amendments Worth Applying
David M. Kopec, Extension Turfgrass Specialist
In the last 3-5 years, a lot of products have come on the market which include humic acids as natural organic fertilizers.
Well, what's all the hub-ub!? First, we have to answer some questions about definitions.
Humus: The more or less stable fraction of the soil that persists as organic matter after the major portion of plant or animal tissues (residues) have decomposed in color. Humus is not the stuff you put on a sandwich (Hummus).
Humification: The process involved in the decomposition of organic matter, and leading to the formation of humus.
Humic Acid: A mixture of variable and indefinite composition of dark organic substances, which when mixed with acid, of a dilute alkali extract from soil, form precipitates (visible glob).
Fulvic Acid: A term of varied usage which usually refers to the mixture of organic substances remaining in solution (stays in water) upon acidification of a dilute alkali extract from soil.
Confused? Here's what they do.
Fulvic and humid acid products are derived from the decomposition of organic matter process. They are very large molecules which have a high cation exchange capacity (CEC).
This means that these organic acids can store lots of positively charged minerals on them (i.e., K+, Ca+, Mg+, Mn+, Na+, etc). It takes lots and lots of fulvic or humic acid to make a difference in soil CEC, by just adding commercial amounts of these acids. Mother nature makes these on their own in lawns. As clippings decompose, and roots regenerate themselves, organic acids are made.
Should you apply humic or fulvic acids to your lawn?
As mentioned before, it takes a lot of acid to change the CEC of soil. If it makes you feel good, do it!
What is the immediate response I get after applying these products C they must be good! Check the label. There may be other fertilizer(s) included in the bottle which can green up the grass quickly. Additions often include urea nitrogen, iron, or ammonium nitrate or sulfates. These elements can green up the turf quickly. Perhaps one benefit is the fact that humic and fulvic acids act as chelating agents. They cling to, and protect iron, zinc, copper and manganese from being tied up in the soil (at our high soil pH values). Thus, they are more plant available. Remember that fulvic or humic acids are part of the organic matter process, and are in effect liquid chemicals. They do not add organic matter per se, as when adding mulch, manure, or cotton trash, etc. Here, the physical matter added is beneficial to soils which have low organic matter. Low organic matter content soils often may have poor soil structure, which is improved by organic matter (as long as it is not applied in layers!).
Remember, if it makes you feel good, do it! If you are perfectly happy with your regular lawn fertilizer program, stay with it!
Issued in furtherance of Cooperative Extension work, acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, James A. Christenson, Director, Cooperative Extension, College of Agriculture & Life Sciences, The University of Arizona. The University of Arizona is an equal opportunity, affirmative action institution. The University does not discriminate on the basis of race, color, religion, sex, national origin, age, disability, veteran status, or sexual orientation in its programs and activities.