Leonardite and Humic Acid
It is theorized that Leonardite shale originated from trees and other vegetation, which grew during the carboniferous period when most of North America was a tropical type forest. Over the ages, the vegetation underwent compaction and heating, slowly carbonizing and forming coal. Through this compaction, organic acids and esters present in the vegetation were squeezed out, forming a pool on top of the lignite bed. This pool dried, aged, and eventually formed Leonardite shale. The vegetative origin of the Leonardite shale indicates this material is humus and contains Humic Acids. The content of Humic Acids within the Leonardite shale is variable with the location of deposits found throughout the world. Those deposits in the North Dakota area are among the most pure in the world containing 80 to 90 percent Humic Acids. Any one of the other sources of Humic Acids, including pear, muck, green, or animal manures, can be beneficial to plant growth when incorporated into the soil. Leonardite shale is an easily available and concentrated form of Humic Acids, making it the subject of much research work and commercial use.
Soil organic matter is plant and animal residues in the soil at various stages of decomposition. Tissue is both the primary source of food for soil microorganisms during decomposition, and the primary source of soil organic matter. When plant tissue is added to the soil three basic actions take place. First, the bulk of the material is converted to carbon dioxide, water, and energy through enzymatic oxidation. Second, elements such as nitrogen, phosphorous and sulfur are either released or immobilized in separate reactions. Third, microbial resistive compounds are formed through modification of compounds in the original plant tissue, or by microbial synthesis. During the enzymatic changes of soil organic matter, simple products, such as carbon dioxide and water, appear immediately. Other products, such as nitrate nitrogen, appear only after the initial peak of vigorous activity has subsided.
Humus is the end product of the microbial decay of organic matter. Humus contains both humic and non-humic material. Humus is relatively stable and fairly resistant to further rapid breakdown. Humus is a tremendous food source for soil microflora. Components of humus are oxidized or mineralized and then utilized by plants. Humus is now known to include a broad spectrum of organic constituents, many of which have their counterparts in biological tissues. It is theorized that humus contains most, if not all, of the biological compounds synthesized by living organisms, including plants.
Humic Acid contributes to plant growth and development by affecting the physical, chemical, and biological properties of the soil. Any given benefit of humus will vary from one soil to another and will depend upon environmental conditions. Humic Acid benefits the physical condition of the soil in many ways. Desirable soil structure, texture, and looseness are promoted, specifically in tight clay soils. Good soil structure with humic acid can help drainage, increase water holding capacity, and raise aeration. When added to the soil, humic acid can act as a buffer by preventing rapid changes in acidity or alkalinity. A more favorable medium for plant root systems is another physical condition that benefits from humic acid.
Humic acid also affects numerous chemical properties in the soil. Humic acid helps chelate micronutrients, increasing the plant uptake. Another chemical benefit of humic acid is increased ion exchange capacity in the soil, which leads to better retention and utilization of minerals and soil nitrogen.
Biological conditions of the soil also benefit from humic acid. Humic acid aids to increase activities of microflora and microfaunal organisms. Many investigators have also observed a positive effect of humic substances on the growth of various groups of microorganism. They attributed this to the presence of Iron in the humic acids and their colloidal nature, or they regarded humic substances as organic catalysts.
Humic Acid and Today’s Farming Industry
Modern day soils have been over-cropped, abused, and depleted of organic matter and certain essential elements. Modern day agricultural practices greatly increase the rate of the utilization and destruction of humic material. Soil humus is not a stable material. Any changes in natural conditions will result in changes in humus content of the soil. Some of these changes are irrigation, drainage, deforestation, annual removal of crops, and normal cultivation of crops. All these changes lead to a rapid and marked change of the humus balance of the affected soil.
The fertilizer industry now recognizes the importance of maintaining the humic content of soils as an aid to increased good productivity. Within recent years many soil management programs have been designed to increase, or at least maintain, the humic materials. The far-sighted grower is also beginning to change his attitude toward the soil. He is faced with many ecological considerations as he encounters today’s problems of pollution, presence of harmful chemicals in treated grains and forage, and depletion of soil organic matter. Modern cultivation practices greatly accelerate the destruction of humic material, which must be replaced in some matter if the productivity of the soil is to be maintained.