Carbon, hydrogen, oxygen, nitrogen, phosphorus and sulphur are the primary elements essential to all life. Soils contain all of these elements in addition to other macro and micronutrients which are needed for plant growth. Typically, such elements are not present in the soil in sufficient quantity or in forms that can support maximum plant growth and yield. In order to overcome these deficiencies, fertilizers having specific chemical constituents in specific amounts are often added to the soil, thereby enriching the growth medium. The fertilizers may be supplemented with certain trace elements such as copper, iron, manganese, zinc, cobalt, molybdenum, and boron, as oxides or salts containing the elements in the cationic form.
Agriculturally, metal ions are essential nutrients for plant growth. Soil deficiency because of the unavailability or exhaustion of metal ions is very often the cause of poor plant growth. Both soil and foliar application of metal ions are routinely used to prevent, correct or minimize soil deficiencies.
The prior art teaches two basic types of fertilizers—fast uptake fertilizers and slow uptake fertilizers. The fast uptake fertilizers are typically liquid fertilizers which are easily assimilated by plants and can be easily and evenly applied either to the soil or directly onto the plants. The slow uptake fertilizers are typically dry fertilizers which are pellets or granules. The dry fertilizers are generally applied to the ground. The dry fertilizers are often coated in either clay or other biodegradable coatings. Over time, typically up to three weeks, the coating decays due to exposure to moisture and other elements, causing the fertilizer to be released into the soil where it is taken up by the plant. Liquid or fluid fertilizers are generally preferred due to the ease of handling, versatility of application and uniform application.
The prior art teaches several examples of liquid fertilizers. For example, U.S. Pat. No. 4,356,021 teaches a liquid fertilizer composed of ammonium thiosulfate and zinc oxide; U.S. Pat. No. 5,372,626 teaches a composition comprising metal ions and citric acid which is applied to plant roots; U.S. Pat. No. 5,997,600 teaches fertilizer additives including chelated metal ions, specifically, metal oxides; and U.S. Pat. No. 4,404,146 teaches a method of making metal oxyalkylates for use in supplying said metal to plants or animals, which involves reacting the metal with carboxylic acid and hydrogen peroxide in an aqueous reaction mixture.
Similarly, the prior art also teaches several examples of slow release fertilizers or coated fertilizers. For example, U.S. Pat. No. 5,435,821 teaches a vegetation enhancement agent comprising a mixture of at least one macronutrient, micronutrient, slow release fertilizer or nitrogen fertilizer and a pesticide, which is then coated with a sulfonated polymer which acts as a controlled release coating; U.S. Pat. No. 5,725,630 teaches a method for preparing a liquid fertilizer containing alkanoic acids which is subsequently mixed with a granular carrier, producing a dry granule fertilizer; U.S. Pat. No. 5,748,936 teaches a process for producing granular fertilizer using a slurry of clay in water, followed by screening to remove granules of undesired size; U.S. Pat. No. 5,002,601 teaches a method for preparing a suspension fertilizer wherein nutrient material and at least one crystal growth inhibitor are mixed with potassium chloride and clay is subsequently added as a suspending aid; and U.S. Pat. No. 6,039,781 teaches a controlled release fertilizer formed from nutrient granules coated in first an organic oil and second a polymeric encapsulating coating.
However, the prior art does not teach a fertilizer or supplement that combines both quick uptake and slow uptake. Furthermore, simply combining a liquid fertilizer and a dry fertilizer as known in the art does not produce a desirable product, due to obvious difficulties with mixing and subsequent application of the product.
The prior art teaches the use of oxide forms of nutrients as slow release liquid fertilizers arranged for foliar application. Typically, the oxides are in a highly basic form. Similarly, the use of sulfate forms of nutrients for quick release fertilizers is also known. However, the sulfates are typically very acidic, meaning that simply combining the oxide fertilizer and the sulfate fertilizer leads to precipitation of nutrients and a non-functional product.
This is a concern, as it is often necessary or desirable to apply fertilizers and/or supplements several times over the course of a growing season. As will be appreciated by one knowledgeable in the art, with each application, there is an inherent risk that damage will occur to the plants, thereby reducing crop value. This does not include the inherent cost involved in dedicating time and resources to the task of fertilizing. Furthermore, with multiple applications, there is significant risk that the required nutrients may not be available during an important stage in the plant's development.
Clearly, a single fertilizer having both short term, quick uptake nutrients and long term, slow uptake nutrients that can be applied in a single application is needed.