Organic matter of soil is one of the most important natural resources. From ancient times, man has recognized that the soil fertility can be maintained or improved by means of organic materials incorporation. Unfortunately, modern practices to handle cultivated soils, as well as irrigation and drainage methods, crop practices and the use of chemical fertilizers have contributed to the exhaustion to such an extent that the presence of organic matter in soils for commercial agriculture has become seriously diminished or nonexistent.
Organic matter in soil is the accumulation of partially decomposed and resynthesized wastes that affect plant nutrition. Organic matter has two main components, humic and non-humic substances. Humic substances constitute 60 to 80% of organic matter in soil and include complex materials that are very resistant to microbial attack. Humic compounds are characterized by their aromatic chains, such as polyphenol and polyquinone, which are very complex structures. These groups are formed by decomposition, synthesis and polymerization. Humic substances do not show clearly defined physical and/or chemical properties; they are amorphous, dark and have high molecular weights from hundreds to thousands. Based on their resistance to degradation and their solubility in acids and alkalis, humic substances have been classified into three chemical groups: (a) fulvic acid, with the lowest molecular weight and lightest color; it is soluble in alkalis and acids and the most susceptible to microbial attack; however, fulvic acid is very stable and more resistant to degradation than other fresh materials recently incorporated; fulvic acid can stay between 15 and 50 years in soil. (b) humic acid with medium color and molecular weight; it is soluble in alkalis and insoluble in acids; it has medium resistance to degradation; (c) humin is the component with highest molecular weight, darkest color, insoluble in alkalis and acids and the most resistant to microbial attack. Usually fulvic acids and humic acids are called “humic acids”.
Non-humic substances group constitutes between 20 to 30% of organic matter of soil. These compounds are less complex and less resistant to microbial attack than those in the humic group. Non-humic substances are formed by specific organic compounds with defined physical and chemical properties. Some of these non-humic materials are modified only by microbial action, while others are synthesized as a result of the breakdown of larger chains of substrates. Non-humic group includes polysaccharides, which are especially effective to form stable aggregates in soil, such as polyuronides that are not found in live plants but that are synthesized by soil microorganisms and are components of microbial tissues. Once the microorganism dies, polyuronides are subject to degradation by other microorganisms or to interaction with other soil materials.
Some simple compounds that are part of non-humic groups are some organic acids and materials with protein-like structures. Although these materials are not present in large amounts, they are essential since they affect availability of some plant nutriments such as nitrogen and iron.
Historically, organic matter in cultivation soils has been regenerated through crop rotation, leguminosae planting and tillage with green manure and through application of composts. However, most of these techniques are expensive and time-consuming. Furthermore, current economic pressures prevent farmers from using sustainable cultivation practices. An analysis of this issue suggests that a fast and practical solution is the identification of a reliable source that provides organic matter for its direct application to soil and, if possible, to the plant itself.
There are in the market some extracts of sources rich in organic matter, that have proven useful for commercial agriculture and that are used to increase contents of organic matter in soil and thereby reestablish fertility in a practical way, resulting in benefits such as soil improvement and physiological activation of crops.
These humic extracts, as well as other non-humic extracts, are obtained in soluble form from different sources by means of chemical agents, mainly alkalis. Resulting aqueous solutions are widely commercialized in the agricultural market. A review of the available literature and commercial catalogs indicates that the main source of humic substances' extraction is fossil carbons such as lignite or its derivatives, commonly known as “mineral” sources, and that are soft carbonaceous materials, earth-like, brown to black, and are related to carbon deposits. These sources are characterized by an unusually high content of “humic acids, about 30 to 60%. High content of this source provides fluid extracts with a content in the range of 12 to 18% of solute “humic acids”.
Other extraction sources for humic substances are commonly called “organic” and include naturally formed substances, such as peat, which consists of organic matter coming mainly from plant detritus and presumably animal wastes and microorganisms trapped in flooded beds. Included in this type of sources we find induced-formation sources such as compost and worm compost, which are materials resulting from composting process, [i.e. degradation of organic wastes of plants and other organisms that were once alive], by means of controlled biological processes that results in an earthy, dark substance with good physical properties and excellent features as organic mends for soil. In this type of sources, degradation is carried out by microorganism; in the case of the worm composts, degradation is promoted by worms, usually Eisenia foetida species, as well as by microorganisms. Concerning mineral sources, solid-state organic sources show low contents of “humic acids”, about 10%, and therefore the extract obtained from these sources reaches maximum percentages of 2 to 3%.
In the practice humic extracts have proven to have positive effects over agricultural production, independently from their source. However, both sources have advantages and drawbacks.
Mineral humic extracts are found in an advanced state of decomposition. Biggest changes observed in this type of extracts include loss of carbohydrates, proteins and other biochemical components, as well as increased oxidation of humic materials. This way, unlike soil humus, mineral humic extracts are essentially free from biologically significant compounds such as proteins and polysaccharides.
The virtual absence of proteins and other biochemical nitrogenous compounds indicates that mineral “humic acids” are not proper sources of nitrogen for plant growth. On the other hand, most monosaccharide gums, the most effective soil humus components to form stable aggregates, are not present in mineral humic extracts. Also, due to their high content of carbon and their extremely condensed structures, mineral “humic acids” are easily immobilized in soil even when applied in soluble state. This means that they have less chance to influence plant growth, acting directly as growth regulators.
The most important contribution of mineral “humic acids” in soil fertility is that they enhance ionic exchange ability and neutralization ability. However, they have the disadvantage that their low concentrations of nitrogen and the advanced oxidation state contributes to reduce microbial populations as nutriments are limited and due to the small amount of available energy for decomposition of other organic substrates when mineral extracts are incorporated to soil.
On the other hand, the primary disadvantage of organic source extracts is the relatively low content of “humic acids” that can be obtained from them in the form of liquid or suspension. This increases significantly production and distribution costs of these materials. The low concentration is the major cause for the decreased competitiveness of extracts prepared from organic sources.
However, “humic acids” obtained from organic sources show very important characteristics to stimulate plant growth, since these are carbonated structures less complex than those obtained from mineral sources. This allows them to be easily absorbed by plants. Since these structures come from a recent synthesis, they do not show an advanced oxidation state and therefore they are chemically more active and provide to plants or soil microorganisms with an energy source for their development.
Another advantage of extracts from organic sources is the presence of microbial populations in significant amounts to beneficiate soils when these extracts are applied, thus helping to reestablish or increase beneficial microorganism populations. This feature enhances plant health and reduces risk of diseases, since, when present in soil or in plant surface, the microorganisms contained in extracts compete for growth factors with pathogenic microorganisms. Also, they excrete antibiotics that contribute directly to reduce undesirable microorganism populations. Another important effect of microorganisms is that they contribute to develop soil fertility in a natural way.
Therefore, a need for joining properties of mineral source extracts and organic source extracts still remains unsatisfied. However, currently the properties of both sources are joined through physical mixtures of commercial products. The operation to carry out the physical mixture reduces the content of properties of each one of the products that are mixed, in a determined volume, thus decreasing their properties and effects, and increasing production and commercialization costs.
For example, if a ½ liter of mineral extract with a content of 18% humic substances is mixed with a ½ liter of an organic extract with a content of 3% humic substances a total volume of 1 liter of solution with a content of 10% humic substances will be obtained, which shall only have half the properties and half the effects, as compared to the original volumes.
In accordance with this invention, the inventor has developed a process to concentrate properties of liquid extracts of both generic sources in a determined volume. Surprisingly the extract obtained shows better properties as compared to extracts obtained separately or physically mixed.
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