The present invention relates to plant growth stimulants containing coal ash and humic acid-bearing ores and more particularly to plant growth stimulants containing fly ash and leonardite ore, an ore composed mainly of the mixed salts of humic acids.
Generally, "humic substances" is used as a generic term for the organic acids derived from humus or the top layer of soil, containing organic decomposition products of vegetation and animal organisms in admixture with inorganic compounds, sands, minerals, metal hydroxide bases, etc. The chemical structure of humic acids has not been established, but they are believed to be large condensed ring, polymer-like molecules containing pendent carboxylic acid phenolic groups. Current research indicates that it is the humic acid found in humus which promotes the chelation of nutrients.
"Humic acids" is generally used as the collective name for the various acid radicals found in humic matter. Thus, depending on their solubilities, humic acids are usually classified as humic acid, fulvic acid and ulmic acid. The singular "humic acid" is used to refer to the acid radical found in humic matter which is soluble in alkali but insoluble in acid, methyl ethyl ketone and methyl alcohol. Fulvic acid, for example, is the acid radical found in humic matter which is soluble in alkali, acid, methyl ethyl ketone and methyl alcohol. Ulmic acid is thus the acid radical found in humic matter which is soluble in alkali and methyl ethyl ketone but insoluble in methyl alcohol. The derivatives of these acids may be dispersed in water where they will hold fertilizer salts in an exchangeable form for plants and act as buffers and chelating agents.
"Humates" are the salts of the various humic acids. Collectively, they posses extremely high ion-exchange capacities and it is this property that makes possible better retention and utilization of fertilizers by preventing excessive leaching away from the root zones and ultimately releasing the fertilizers to the growing plants as needed. Humates also reduce soil erosion by increasing the cohesive forces of the very fine soil particles. Humates or humic acids thus not only greatly improve the texture and tilth of soils but actually help to mobilize and release nutrients otherwise unavailable to plants.
Humic acids are known to posses many beneficial agricultural properties: they participate actively in the decomposition of organic matter, rocks and minerals, improve soil structure and change physical properties of soil, raise exchange capacity and buffering qualities, promote the chelation of many elements and make these available to plants, aid in correcting plant chlorosis, act as an organic catalyst, increase the permeability of plant membranes, improve growth of various groups of beneficial microorganisms, intensify enzyme systems of plants and grass, accelerate cell division and increase germination capacity of seeds, show greater root development and decrease stress deterioration, produce stronger and healthier plants, aid in resisting plant disease better, reduce toxic sodium and pull sodium from clay particles, break the calcium-iron-phosphate bond and activate their benefits to plants, improve growth and vigor, prolong fruit and flower bearing capacity and retain moisture and nutrients in root zone areas. Thus, practically all modern soil management practices for garden and crop production are designed to increase the content of humic acids in the soil. In addition, the fertilizer industry has long emphasized the importance of maintaining the humic content of soils to ensure good productivity since humic matter is continuously being formed in soils, and at the same time, is being continuously destroyed.
Humic acids, like organic compounds of an individual nature, promote the conversion of a number of elements into forms available to plants. Humates thus aid in supplying growing plants with food. However, they serve in much more important ways to make soils more productive and farming more profitable. One of their most significant properties is that they increase the water holding capacity of soils. Thus, soils that contain relatively large amounts of humate material resist droughts more effectively and produce better yields where rainfall or irrigation may be insufficient.
Leonardite ore, also known as humate ore, is a believed to be an oxidized form of lignite coal which is mainly composed of the mixed salts of humic acids. It is unique in that it comprises decomposed vegetable growth and animal waste. Leonardire ore is a well-known source of humic acid and a wide variety of humates. It has also long been known to be a source of organic material adapted for use as soil and foliar additives having application in the regulation of plant growth. Moreover, it contains significant amounts of humic acid fractions, such as humic, ulmic & fulvic acids, that are vital to plant life.
Coal ash is another valuable substance which provides for the proper growth of plants. It consists of the inorganic mineral constituents in the coal and some organic matter which is not wholly burned. The inorganic mineral constituents, whose residue is ash, make up from 3% to 30% of the coal. During combustion, this ash is distributed into two parts; bottom ash collected from the bottom of the boiler unit, also sometimes referred to as bed ash or boiler slag, and fly ash, most of which is collected by air pollution control equipment. Fly ash makes up from 10% to 85% of the coal ash residue and occurs as spherical particles, usually ranging in diameter from 0.5 to 100 microns. The bottom ash, composed primarily of coarser, heavier particles than the fly ash, ranges from gray to black in color and is generally angular with a porous surface. The distribution of ash between the bottom and fly ash fraction is a function of the boiler type, coal type and whether or not a wet or dry bottom furnace was used.
Coal ash contains many of the minor and micro nutrients needed for effective plant growth. There are fourteen mineral elements which are essential to the growth of some plant or plants; calcium, magnesium, potassium, iron, manganese, molybdenum, copper, boron, zinc, chlorine, sodium, cobalt, vanadium and silicone. While all are not required for all plants, all have been found to be essential to some. These mineral elements, in addition to phosphorous and sulfur, usually constitute what is known as the plant ash, or minerals remaining after the burning off of carbon, hydrogen, oxygen and nitrogen.
The chemical elements nitrogen, phosphorous and potassium are known as macro-nutrients, which are required in the greatest quantity. Sulfur, calcium and magnesium, called secondary elements, are also necessary to the health and growth of vegetation, but they are required in lesser quantities compared to the macro-nutrients. The other elements of agronomic importance, provided for plant ingestion in small (or trace) amounts, include boron, cobalt, copper, iron, manganese, molybdenum and zinc. These minor elements are called micro-nutrients.
If one compares the elements found in coal ash residues to the list of elements required for plant nutrition, one finds considerable overlap. Tables I and II show the variation in coal ash compositions with coal rank and the chemical characteristics of coal and coal ash.
TABLE I ______________________________________ VARIATION IN COAL ASH COMPOSITION WITH COAL RANK Chemical Coal Rank, Percent Constituent Anthracite Bituminous Subbituminous Lignite ______________________________________ SiO.sub.2 48-68 7-68 7-58 6-40 Al.sub.2 O.sub.3 25-44 4-39 4-35 4-26 Fe.sub.2 O.sub.3 2-10 2-44 3-19 1-34 TiO.sub.2 1.0-2.0 0.5-4 0.6-2 0.0-0.8 CaO 0.2-4 0.7-36 2.2-52 12.4-52 MgO 0.2-1 0.1-4 0.5-8 2.8-4 Na.sub.2 O -- 0.2-4 -- 0.2-28 K.sub.2 O -- 0.2-4 -- 0.1-1.3 SO.sub.3 0.1-1 0.1-32 3.0-16 8.3-32 ______________________________________
TABLE II ______________________________________ TRACE ELEMENTS IN COAL AND COAL ASH FROM DEPOSITS AROUND THE WORLD Coal Ash Element (ppm) (ppm) ______________________________________ Antimony 10-30 100-3,000 Arsenic 0.8-500 280-10,000 Barium 2-257 18-2,200 Beryllium &lt;0.1-40 1-4,000 Bismuth 0-100 0-2,000 Boron 15-156 52-10,000 Chlorine 30-560 Chromium &lt;0.1-50 &lt;0.1-7,400 Cobalt &lt;0.4-34 &lt;5-2,000 Copper 2.6-185 10-1,200 Fluorine 40-480 Gallium &lt;1.4-100 10-3,200 Germanium &lt;0.4-50 9-47,000 Iodine 1.11 Lanthanum &lt;1.5-40 &lt;30-700 Lead 25-3,000 200-31,000 Manganese 9-&gt;5,000 100-22,000 Mercury 0.001-300 Molybdenum &lt;0.7-200 &lt;5-6,000 Nickel 0.42-&gt;60 &lt;5-16,000 Palladium 0.2 Platinum 0.7 Rhodium 0.02 Silver 0-3 0-60 Strontium 0-100 0-&gt;1,000 Scandium 60-400 Tin &lt;0.1-300 0.4-6,000 Titanium 95-2.320 100-35,000 Uranium 0-24,000 6-1,650 Vanadium &lt;1.4-&gt;100 &lt;10-25,000 Yitrium &lt;0.1-49 &lt;10-2,000 Zinc 7.6-2,000 115-21,000 Zirconium 0-140 0-7,000 ______________________________________
When comparing the elements of coal ash residues and the required elements for plant growth, it is found that only sufficient quantities of nitrogen, phosphorous and chlorine are not available in fly ash residues and perhaps sufficient potassium depending on the origin of the coal ash.
Coal ash has been used in fertilizer compositions, wherein the nutrients in the ash have been chemically modified. For example, U.S. Pat. No. 4,469,503; issued to R. F. Stockel, discloses a fertilizer composition which comprises coal ash and a relatively water-insoluble polymer capable of gradually decomposing to slowly release nitrogen. The polymer is formed by the in situ polymerization of an aldehyde and a polymerizable organic nitrogen.
Similarly, humic acid containing material such as peats, humates, lignites, leonardite and the like have been proposed heretofore for use as ingredients of plant fertilizer compositions, although it has previously been necessary to extract the humic acids from the ore prior to their use. For example, U.S. Pat. No. 4,698,090; issued to J. R. Marihart discloses a process for preparation of compositions for modifying plant growth, including extracting humic acids by the reaction of organic chelating agents with leonardite ore.
To achieve an effective fertilizer, it is necessary to transform some of the elements found in coal ash residue into desirable chemical moieties. The constituents of coal ash, however complete, must be in the form in which plants can use them. The mere presence of particular chemical elements in the soil is not enough. The problem of maintaining optimum growing conditions is to have the essential elements not only present, but in a form readily available to each plant's requirements. Although both coal ash and humate ores have previously been used individually for various agricultural purposes, there still exists a need for a convenient and complete plant growth stimulant, which can adequately provide and convert the required nutrients into the proper form.