organic matter (whether they degrade it or stabilize it). Compost, aged manure and work casting are examples of active organic matter soil amendments. While these products are great for feeding soil microbes and loosening up the soil, they are quickly degraded by soil microbes. Stable organic matter is the component of soil organic matter that is no longer being degraded by soil microbes. Humic acid, for example, is a stable organic matter that persists in the soil for decades and centuries. Humic acids are the decomposed remnants of living organisms, similar to extremely old compost and, for the most part, are fully digested by soil microbes. The sequestered carbon that builds up in the topsoil over centuries is primarily humic substances like humic acid. These stable organic acids are typically described by their molecular weight and can be separated into three subgroups: fulvic, humic and humin.
Why Amend? The construction and landscaping process disturbs the topsoil to the extent that much of the carbon stored in the topsoil is no longer where it should be. Often, the approach is to add some compost or wood shavings to replace the lost soil organic matter. The problem with this approach is that the soil microbes actively digest these amendments. As much as 60 to 80 percent of compost or manure is digested by soil microbes and lost within the first year, leaving the soil and entering the air as carbon dioxide. Humic acids are stable and persist in the soil for decades after application. Humic acids in a granular form are called humates. Commercially available humates are derived from mined ore deposits, which are an accumulation of ancient plant material. Humates spread like fertilizer and work well as a soil amendment. Broadcast applications of
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humate on established plants and turf work well, but more soil incorporation is encouraged on new installations. Water conservation is greatly impacted by soil organic matter. How does it do this? The answer has to do with how the organic matters loosens the soil by forming aggregates. The space between the aggregates is called porosity. Organic matter increases soil porosity by adding macropores and micropores to a soil profile. This additional space in the soil allows it more room for air and water conservation. Humates contribute to passive soil organic matter. The application of humate in the soil can release plants’ nutrients that used to be locked up. Because humates can release and store nutrients, manufacturers will often blend humates with fertilizers. When purchasing humates, look at the label for additional ingredients that may have been added. One beneficial characteristic of soil organic matter is its high cation exchange capacity, commonly referred
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to as CEC. Fertilizers are made up of two components, and each has a positive and negative charge. The positively charged fertilizer components are called cations. This means that some fertilizers are attracted to soil organic matter, meaning they help store the nutrient. By increasing CEC, more fertilizer is stored, which helps keep nutrients available to ensure plants are healthy and growing. Storing fertilizer longer in the soil also reduces the runoff of plant nutrients into rivers, lakes and oceans. Humates are used for the following purposes: to add stable organic matter to the soil, make more efficient use of applied fertilizer and water, condition clay and sandy soils and mitigate the effects of salts. The longterm impact of humates complements conservation goals, making them a wise choice for the property owner.
Russell Taylor
Vice President Live Earth Products
