Chemistry: fertilizers – Processes and products – Inorganic material
Reexamination Certificate
2000-09-22
2002-12-03
Sayala, Chhaya D. (Department: 1761)
Chemistry: fertilizers
Processes and products
Inorganic material
C071S044000, C071S047000, C071S051000, C071S052000, C071S053000, C071S063000
Reexamination Certificate
active
06488735
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority to Italian Application Ser. No. M099A000207 filed Sep. 30, 1999, the disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a fertilizer compound having a glass matrix.
It is known that fertilizer elements, i.e. the elements that provide the nutrients required for the growth of crops, are divided into three categories: primary elements, i.e. nitrogen (N), phosphorus (P) and potassium (K); secondary elements, i.e. calcium (Ca), magnesium (Mg), sodium (Na) and sulfur (S); and trace elements, i.e. boron (B), cobalt (Co), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo) and zinc (Zn).
This division is based on the amount of element absorbed by the crops, not on their function, since all these elements are equally indispensable for the balanced growth of plants.
The above-cited elements are the ones that currently can be listed on the label as components of a formula according to the standards prescribed by applicable national and European Union statutory provisions.
Fertilizer elements have a decisive effect on the growth of crops both when they are insufficiently available and when they are in excess, causing on the one hand poor nutrition of the crops and on the other hand a toxic condition.
It is therefore necessary to ensure, for each crop, the presence and availability over time of these elements, so that the soil contains them in quantities which are adequate but contained within very precise and controllable limits, depending on the requirements and the development stage of the crop.
It is also noted that a same soil is alternately used, for periods of varying duration, for different crops which absorb different amounts of nutrient both in qualitative and in quantitative terms.
It is therefore indispensable to periodically balance the resources of the soil in relation to the changes in requirements.
Moreover, the controlled presence of fertilizing elements in agricultural soils affects not only the life and growth of plants but also decisively controls the commercial characteristics of foodstuffs designed for human consumption.
In order to compensate for the nutritional imbalances that are widespread in most soils adapted for products for human use it is necessary to supply agricultural soils not only with the primary elements (N, P and K) and the secondary ones (Ca, Mg, Na, S) but also with the trace elements (B. Co, Cu, Fe, Mn, Mo, Zn).
Selective administration of the trace elements must occur at programmed times and in preset amounts according to the type of crop, the stage of its growth and the characteristics of the cultivated soil.
Several methods are known for introducing fertilizers in general, and particularly trace elements, in the soil.
The foremost consists in adding to fertilizers based on nitrogen, phosphorus and potassium (NPK) small amounts of the particular trace elements deemed to be lacking in the soil to be cultivated.
These trace elements are introduced in the form of inorganic salts (sulfates, oxides or others) or in the form of metal-organic complexes known as chelates, which are synthesis products highly water-soluble and hence highly assimilated by the plant.
This method is not devoid of drawbacks, the foremost being the immediate availability of the trace elements for absorption by the plants in excessive amounts and over periods which are not correlated to their growth cycle and the considerable leakage of nutrients into the environment due to rainwater and irrigation water.
In order to obviate these drawbacks, controlled-solubility fertilizers have been introduced which are obtained by encapsulating granules of the fertilizing formulas with low-solubility organic products.
However, even this system suffer drawbacks: since the trace elements are introduced, in this case also, in the form of inorganic salts and/or chelates which are water-soluble, they are rapidly assimilated by the root system of the plants and/or dispersed in the soil once the outer coating has degraded.
For the same reason, these fertilizers are useful only if rapid nutrient action is required; if instead one wishes to ensure their presence in the soil for long periods, it is necessary to resort to multiple successive low-dosage applications of the same products, entailing a consequent increase in field operating costs.
Finally, it is necessary to note the high intrinsic cost of these fertilizers, since each chelate normally adds a single trace element, so that if it is necessary to administer multiple elements it is also necessary to use several chelates.
The problems linked to the use of inorganic salts and/or chelates of trace elements have been partially obviated by introducing FTE (Fritted Trace Element) fertilizers.
These products have a predominantly amorphous structure and are constituted by a glass matrix which acts as substrate and in which one or more trace elements are dispersed and bonded.
The solubilization of the product, and therefore the release of the trace elements contained therein, depend on the chemical composition of the glass matrix in relation to the conditions of the soil in which the fertilizer is dispersed (humidity, pH).
It is known that the water-solubility of glass is poor; accordingly, FTEs are products which ensure very slow selective and controlled release of one or more trace elements over time, so as to potentially affect the entire life span of perennial plants or a considerable series of successive crops (up to 10 years).
Known FTEs suffer the drawback that they cannot be used as short-term fertilizers with immediate assimilation due to their poor solubility and consequent slow release action.
The aim of the present invention is to eliminate the above-noted drawbacks of conventional types of fertilizer, by devising a fertilizer compound having a glass matrix which allows to achieve selective release of nutrients whose action is immediate from the beginning of the application and is programmable, controllable and extendible over time, allows to add to the soil, in precise times and amounts, the chemical elements that are necessary for the growth of the plant being cultivated, in relation both to the state of its growth and to the physical-chemical conditions of the soil, and has a low cost.
SUMMARY OF THE INVENTION
These and other objects which will become better apparent hereinafter are achieved according to the present invention by a fertilizer compound having a glass matrix which is characterized in that it comprises, among the forming oxides of said glass matrix, a phosphorus pentoxide (P
2
O
5
) as partial and/or full replacement of silica (SiO
2
); among the modifier oxides is of said glass matrix, a potassium oxide (K
2
O) as partial and/or full replacement of sodium oxide (Na
2
O); and one or more trace elements.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Advantageously, in addition to the phosphorus pentoxide and the silica, the forming oxides comprise alumina (Al
2
O
3
), titanium dioxide (TiO
2
) and zirconium dioxide (ZrO
2
).
Preferably, in addition to the potassium oxide and sodium oxide, the modifier oxides comprise oxides of calcium (CaO), magnesium (MgO), barium (BaO) and lithium (Li
2
O).
As regards trace elements or micro-elements, they are preferably constituted by boron (B), cobalt (Co), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo) and zinc (Zn) and are introduced in the following preferred percentages:
B
2
O
3
: 9 to 18%; CoO: 0.5 to 0.1%; CuO: 4 to 0.1%; Fe
2
O
3
: 11 to 2%; MnO: 9 to 1%; MoO: 0.5 to 0.1%; and ZnO: 8 to 2%.
The stability of the glass matrix of the compound according to the invention depends on a series of chemical and technological parameters: in the specific case, in particular, the key role is played by the presence of the phosphorus pentoxide (P
2
O
5
) as replacement of silica in the role of glassy network forming oxide, allowing to control the solubility characteristics in the various solvents at various pH levels.
Moreover, the fact should not be
Ambri Franco
Macchioni Giuseppe
Marazzi Giovanni
Sayala Chhaya D.
Wolf Greenfield & Sacks P.C.
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