WO1991009818A1

WO1991009818A1 - Micronutrient fertilizer composition

Info

Publication number: WO1991009818A1
Application number: PCT/DK1991/000003
Authority: WO
Inventors: Otto DANNESKIOLD-SAMSØE
Original assignee: Danneskiold Samsoee Otto
Priority date: 1990-01-04
Filing date: 1991-01-04
Publication date: 1991-07-11
Also published as: AU642201B2; AU7060791A; DK1890D0; LV10707A; LT3610B; NZ236673A; HU9202223D0; HUT63594A; LV10707B; CA2072372A1; LTIP795A; EP0509030A1

Abstract

A micronutrient fertilizer composition in the form of dry aggregate bodies, the fertilizer composition being adapted to be mixed with a macronutrient fertilizer composition, each aggregate body comprising salts of at least two metals selected from the group consisting Cu, Mn, Zn, Co and Mo as well as at least one water-soluble nitrate which is not in the form of a salt of the above-mentioned metals, the ratio between micronutrients and macronutrients in the micronutrient fertilizer composition being substantially above the ratio in which the micronutrients and macronutrients in question are required by crop plants; a method for preparing the micronutrient fertilizer composition; solid micronutrient fertilizer composition containing the micronutrient fertilizer composition; and a method for fertilizing crops using the micronutrient fertilizer composition. The composition is easily applied to crops or soil together with standard commercial macronutrient fertilizers and is readily soluble in water and easily absorbed by crop plants.

Description

MICRONUTRIENT FERTILIZER COMPOSITION

FIELD OF THE INVENTION

The present invention relates to a solid micronutrient fertilizer composition comprising micronutrients in the form of metal salts together with at least one water-soluble nitrate, to a method for preparing the micronutrient fertilizer composition, and to a method for fertilizing crops using the micronutrient fertilizer composition.

BACKGROUND OF THE INVENTION

It is well-known in the field of agriculture that the optimum devel- opment of plants is dependent upon the plants being provided with the proper balance of all of the various essential nutrients. The lack of just a single essential nutrient, which perhaps is only necessary for proper growth in extremely small quantities, can lead to poor growth, deficiency symptoms and a drastic reduction in crop yield. Even though all of the other essential nutrients may be present in optimum quantities, the one nutrient which is present in a sub-optimum quan¬ tity may thus become the limiting factor, thereby seriously retarding the development of the plants.

On the other hand, less is known about how the various micronutrients are to be provided so as to be available to the plants in suitable amounts, thereby securing optimum growth, while at the same time being in a form which allows them to be applied in a practical and economical manner. Thus, the lack of a practical and economical way of applying readily available micronutrients to, or example, field crops may result in the crops receiving a sub-optimum amount of certain essential micronutrients.

Standard macronutrient fertilizers, e.g. nitrogenous fertilizers or N-P-K fertilizers, often lack a number of the essential micronutri¬ ents, although this may not present any acute, readily apparent problem, since most soils contain a certain reserve of these micro¬ nutrients. However, if the soil is not replenished with these micro¬ nutrients, the result in the long run will be a depletion of the micronutrients and therefore a reduced yield. It is therefore neces- sary to provide the essential micronutrients on a regular basis in order to sustain optimum plant growth and maximum yields. This often presents a problem in practice, however, since it often proves dif¬ ficult to apply fertilizer compositions In a form which is readily available to the plants and which also satisfies the requirement that the micronutrients must be relatively inexpensive and convenient to apply.

Thus, a micronutrient fertilizer composition should fulfill the following criteria in order to secure the best effect and optimum plant growth:

1) it should contain a number of the essential micronutrients, and preferably all of the essential micronutrients which are not readily available from the soil;

2) it should be formulated and applied so as to ensure the best possible absorption of the micronutrients by the plant;

3) it should be applied at the proper time in relation to the growth of the plant, i.e. especially at the beginning of the plant's growth cycle and when the soil temperature is at least about 5°C; and

4) It is desirable that it can be applied together with standard commercial nitrogenous or N-P-K fertilizers, and that it is relatively inexpensive.

It has now been found that crop plants can easily and inexpensively be provided with a suitable balance of the essential micronutrients in a readily available form by means of a novel solid micronutrient fertilizer composition comprising the micronutrients in the form of metal salts together with at least one water-soluble nitrate. BRIEF DESCRIPTION OF THE INVENTION

One aspect of the invention relates to a micronutrient fertilizer composition in the form of dry aggregate bodies, the fertilizer composition being adapted to be mixed with a macronutrient fertilizer composition, each aggregate body comprising salts of at least 2 metals selected from the group consisting of Cu in an amount of 300- 15,000 g per 100 kg of the composition, exclusive of any binder, Mn in an amount of 150-8000 g per 100 kg of the composition, exclusive of any binder, Zn in an amount of 50-4000 g per 100 kg of the com- position, exclusive of any binder, Co in an amount of 1-200 g per 100 kg of the composition, exclusive of any binder, and Mo in an amount of 5-500 g per 100 kg of the composition, exclusive of any binder, as well as at least one water-soluble nitrate which is not in the form of a salt of the above-mentioned metals, the ratio between micronutrients and macronutrients in the micronutrient fertilizer composition being substantially above the ratio in which the micro¬ nutrients and macronutrients in question are required by crop plants.

A second aspect of the present invention relates to a method for preparing a micronutrient fertilizer composition in the form of dry aggregate bodies which are adapted to be mixed with a macronutrient fertilizer composition, the method comprising dry mixing without any substantial addition of water salts of at least 2 metals selected from the group consisting of Cu, Mn, Zn, Co and Mo as well as at least one water-soluble nitrate which is not in the form of a salt of said metals, said salts and said nitrate being in the form of pow¬ ders, the ratio between said micronutrients and said macronutrients being substantially above the ratio in which said micronutrients and said macronutrients are required by crop plants, to obtain an in¬ timately mixed micronutrient mixture, and mixing the resulting micro- nutrient mixture with a binder to obtain said micronutrient fertili¬ zer composition in the form of dry aggregate bodies.

A third aspect of the invention relates to a solid fertilizer mixture comprising, as a first component, the above solid micronutrient fertilizer composition, and as a second component, a solid macro¬ nutrient fertilizer composition comprising at least N, P and/or K.

A fourth aspect of the invention relates to a method for fertilizing crops, the method comprising applying to the crops or to the soil the above fertilizer mixture or the above micronutrient fertilizer com¬ position.

The micronutrient fertilizer composition according to the invention fulfills all of the above-mentioned criteria, i.e. it contains sever- al or all of the essential micronutrients in a form which ensures effective absorption by the plants, it is easily applied at the desired time together with, e.g., standard commercial nitrogenous or N-P-K fertilizers, and it is formulated from micronutrient-containing compounds which are relatively inexpensive. Furthermore, as shown below in the Examples, the value of the novel micronutrient fertili¬ zer composition has been proven by significantly increased yields in field trials over several years.

DETAILED DISCLOSURE OF THE INVENTION

The terms "micronutrient fertilizer composition" and "fertilizer composition of the invention" refer to the above-mentioned composi¬ tion comprising micronutrients in the form of metal salts together with at least one water-soluble nitrate. It is clear that the compo¬ sition will also contain nitrogen, and it will typically also contain a certain amount of various macronutrients, but the ratio of micro- nutrients to macronutrients in the fertilizer composition will be substantially higher than the ratio in which the nutrients in ques¬ tion are required by crop plants. The micronutrient fertilizer com¬ position of the invention is, in other words, not designed to be used alone as the sole fertilizer for a crop, but rather together with, e.g., a commercial macronutrient fertilizer. While the amounts of the various micronutrients required by different plants may vary, micro¬ nutrients are by definition those nutrients which are required in only very small amounts, and these amounts lie within certain ranges which are known by persons skilled in the art. For field crops, the following macro- and micronutrients are typically required in the following- mounts (per hectare per year) :

Macronutrients Micronutrients

With reference to the above amounts of nutrients typically required in field crops, the term "the ratio between micronutrients and macro¬ nutrients in the micronutrient fertilizer composition being substan- tially above the ratio in which the micronutrients and macronutrients in question are required by crop plants" refers to the fact that the ratio between the micronutrients and macronutrients in the composi¬ tion is typically at least twice the ratio in which the micronutri¬ ents and macronutrients in question are required by the plants, more typically at least 10 times this ratio, more typically at least 20 times this ratio, more typically at least 50 times this ratio, such as at least 100 times this ratio, as will be evident from the above amounts and from that which is described herein with reference to the individual micronutrients as well as from the examples.

While the fertilizer composition in certain cases may be applied alone, it is particularly adapted to be used as a supplement to standard macronutrient fertilizers, for example N-P-K fertilizers or nitrogenous fertilizers, since these fertilizers typically are not designed to provide essential micronutrients.

The term "macronutrient fertilizer composition" refers to a standard fertilizer composition adapted mainly for providing one or more of the important macronutrients, in particular N, P and/or K. Such fertilizers, for example commercial N-P-K fertilizers or nitrogenous fertilizers, are applied in relatively large amounts to crop plants or soil in order to satisfy the plants' requirements for the major nutrients. However, as explained above, these fertilizers often lack a number of the essential micronutrients, or the micronutrients may be present in a form which does not allow absorption in sufficient quantities by the plants.

The expression "water-soluble nitrate" refers to a nitrate which is readily soluble in water. The water-soluble nitrates used in the context of the present invention will furthermore be those which are agriculturally acceptable. In particular, the water-soluble nitrate may be an alkali or alkaline earth metal nitrate, e.g. sodium ni¬ trate, potassium nitrate or calcium nitrate, or ammonium nitrate. The fertilizer composition of the invention may of course contain two or more of such water-soluble nitrates as well as water-soluble nitrates other than the above-mentioned, for example calcium ammonium nitrate.

As mentioned above, the fertilizer composition of the invention comprises salts of at least 2 metals selected from the group consist¬ ing of Cu, Mn, Zn, Co and Mo. However, since all of these metals belong to the group of essential micronutrients, the fertilizer composition will typically comprise salts of at least 3 of the me¬ tals, more typically salts of at least 4 of the metals. A particular¬ ly preferred fertilizer composition is one which comprises salts of all 5 metals.

In addition to the above-mentioned micronutrients, it may be desir¬ able to incorporate certain other important micronutrients into the fertilizer composition of the invention. These include B, Fe, Cl, Na, and I, and perhaps Se, Rb, Ag, Ti and V. In particular, It may be desirable to include a boron-containing salt and/or an iron salt in the fertilizer composition, as both of these elements are essential micronutrients which may be lacking in certain cases. It may further be of interest to incorporate into the fertilizer composition certain elements which are not believed to be essential micronutrients for the majority of plant species, but which are essential for humans and animals, e.g. selenium. It will be understood by a person skilled in the art that the precise content of the various micronutrients in the micronutrient fertilizer composition may vary considerably according to such factors as the type of soil, the crop being grown, the climate and the particular mixture of micronutrients desired based on these and other factors. Therefore, it is difficult to provide general guidelines as to speci¬ fic amounts of different nutrients which will be present in the fertilizer composition in all cases. However, the following amounts (calculated on the basis of the weight of the nutrient element (atom) in question) are provided as a general non-limiting guideline as to amounts which are believed to be suitable for a wide variety of soils, crops and climates. The specific amounts of the various micro¬ nutrients to be used in each particular case will able to be deter¬ mined by a person skilled in the art, for example on the basis of the results of an analysis of the nutrient status of the soil and/or plants, taking into consideration the other factors mentioned above.

When a copper compound is present in the fertilizer composition of the invention, the amount of Cu will typically be about 300-15,000 g, more typically about 1000-8000 g, such^' as about 2000-5000 g, per 100 kg of the micronutrient fertilizer composition, exclusive of any binder. When a manganese compound is present in the fertilizer com¬ position of the invention, the amount of Mn will typically be about 150-8000 g, more typically about 500-3000 g, such as about 1000- 2000 g, per 100 kg of the micronutrient fertilizer composition, exclusive of any binder-. hen a zinc compound is present in the fertilizer composition of the invention, the amount of Zn will typi¬ cally be about 50-4000 g, more typically about 150-2500 g, such as about 300-1500 g, per 100 kg of the micronutrient fertilizer composi-_ tion, exclusive of any binder. When a molybdenum compound is present in the fertilizer composition of the invention, the amount of Mo will typically be about 5-500 g, more typically about 10-300 g, such as about 20-150 g, per 100 kg of the micronutrient fertilizer composi¬ tion, exclusive of any binder. When a cobalt compound is present in the fertilizer composition of the invention, the amount of Co will typically be about 1-200 g, more typically about 5-100 g, such as about 10-50 g, per 100 kg of the micronutrient fertilizer composi¬ tion, exclusive of any binder.

Furthermore, when a boron-containing compound is present in the fertilizer composition of the invention, the amount of B will typi- cally be about 100-7000 g, more typically about 500-4000 g, such as about 1000-2000 g, per 100 kg of the micronutrient fertilizer compo¬ sition, exclusive of any binder. When an Iron compound is present in the fertilizer composition of the invention, the amount of Fe will typically be about 100-6000 g, more typically about 500-3500 g, such as about 750-1750 g, per 100 kg of the micronutrient fertilizer composition, exclusive of any binder.

Similarly, it is difficult to provide general guidelines as to speci¬ fic amounts of the water-soluble nitrate to be used, again due to the variables mentioned above. However, it is believed that in most cases, a suitable amount of N (calculated as pure N) in the form of one or more water soluble nitrates will be about 500-25,000 g, typi¬ cally about 1000-15,000 g, such as about 2000-10,000 g, per 100 kg of the micronutrient fertilizer composition, exclusive of any binder.

In connection with the amounts of the various micronutrients and NO3-N mentioned above, it will be clear to a person skilled in the art that the amount of the micronutrient fertilizer composition to be applied to the soil or to the plants must be chosen according to the quantities of the various nutrients in the fertilizer composition, taking into consideration that while the micronutrients are essential in small quantities for optimum growth, they may also be damaging or even toxic to the plants if applied in excessive amounts.

As mentioned above, the micronutrient fertilizer composition will in addition to a number of micronutrients also contain certain macro¬ nutrients. One of these is obviously N, since the fertilizer composi- tion comprises at least one water-soluble nitrate. In addition, the fertilizer composition will typically contain one or more of the macronutrients S, P, Mg, Ca and K, for example in the form of diam- monium phosphate, potassium phosphate, potassium chloride, potassium sulfate and/or magnesium sulfate. The metal salts of the fertilizer composition of the invention will typically comprise sulfates, nitrates and/or oxides. The metal salts may also be in the form of halogenides (e.g. chlorides), hydrogen sulfates, carbonates and/or hydrogen carbonates. In addition, copper may be present in the fertilizer composition in the form of, e.g., copper oxychloride, and molybdenum may be present in the form of, e.g. , ammonium molybdate or sodium molybdate.

In particular, one or more of the metal salts will often be a sul¬ fate, since sulfate salts of a number of the above-mentioned metals are relatively inexpensive, and since it has been shown that the desired results may be achieved by the use of such sulfates.

Thus, a preferred fertilizer composition according to the present invention comprises at least copper sulfate or copper oxychloride, manganese sulfate and zinc sulfate.

The fertilizer composition of the invention furthermore advantageous¬ ly comprises at least one compound selected from the group consisting of iron (II) sulfate, Solubor® (soluble sodium borate, Na₂B30^3-4^0) , borax, ammonium molybdate, sodium molybdate and cobalt sulfate.

As mentioned above, micronutrient fertilizer compositions according to the invention may be prepared by a method comprising dry mixing without any substantial addition of water salts of at least 2 metals selected from the group consisting of Cu, Mn, Zn, Co and Mo as well as at least one water-soluble nitrate which is not in the form of a salt of said metals, said salts and said nitrate being in the form of powders, the ratio between said micronutrients and said macronutri¬ ents being substantially above the ratio in which said micronutrients and said macronutrients are required by crop plants, to obtain a micronutrient mixture, and mixing the resulting micronutrient mixture with a binder to obtain said micronutrient fertilizer composition in the form of dry aggregate bodies. The term "mixing without any substantial addition of water" refers to the fact the mixing of the metal salts and the nitrate is carried out using a dry process. Thus, while it in certain cases may be desirable to use a certain amount of water in the production process, this amount will generally be quite limited, so that the metal salts and nitrate will not be processed as, e.g., solutions or pastes.

The term "powders" refers to the fact that the metal salts and the nitrate are substantially in the form of powders containing discrete fine dry particles of the materials in question. This term is also meant to include, e.g., materials having a somewhat grainy consisten¬ cy.

While it is possible to mix the powdery micronutrient mixture with the binder immediately after the powdery mixture is obtained, it is preferred that the micronutrient mixture having a powdery consistency is allowed to stand, prior to mixing with the binder, until its consistency has changed from a dry, powdery consistency to a moist, sandy consistency and until the individual particles of said mixture have acquired a crystalline or crystal-like appearance. It has thus been found that the beneficial effect of the micronutrient fertilizer composition is improved if the powdery mixture is allowed to stand for a period of time prior to mixing with the binder. This time period Is preferably at least about 2 weeks, more preferably at least about 4 weeks, most preferably at least about 6 weeks. During this "aging" period, the hygroscopic salts of the mixture absorb moisture from the air, whereby the mixture acquires the above-mentioned moist, sandy consistency and crystalline appearance, thereby making it easier to process than a powdery mixture. It has been found that after a period of about 6 weeks or more at ambient temperature and humidity, the micronutrient mixture, which was originally in the form of a powder, generally has acquired the desired crystalline appear¬ ance and a consistency resembling that of slightly moist sand.

While not being a preferred method, it is contemplated that the micronutrient mixture having a powdery consistency, in addition to or as an alternative to being allowed to stand prior to mixing with the binder, may be moistened with water and subsequently mixed so as to distribute the water uniformly throughout the mixture, thereby achieving the desired moist consistency.

It will be clear to a person skilled in the art that the salts and nitrate used for preparing the micronutrient mixture will typically be sieved and/or ground as necessary before mixing and/or after mixing.

While not wishing to be bound by any particular theory, it is believed that the beneficial effect of the micronutrient fertilizer composition of the invention is obtained as explained in the follow- ing.

It is well-known that in order to obtain the benefit of micronutri¬ ents which are applied to crop plants or to the soil, it is necessary for the micronutrients to be in a form which is easily absorbed by the plants. This in turn means that the micronutrients must be readi- ly soluble in water. This may seem to be relatively straightforward in principle, but in practice difficulties are presented by, among other things, the fact that the desired readily soluble metal salts are hygroscopic and therefore are difficult to formulate in a form which is easily applied to the plants or soil. On the other hand, formulations of the micronutrients which are easily applied, e.g. using lime, may suffer from the disadvantage of being less soluble and therefore less available to the plants.

The novel micronutrient fertilizer composition of the invention is at the same time both easy to apply and readily soluble in water and therefore readily absorbed by plants. The formulation of the metal salts and the water-soluble nitrate together with a binder allows the fertilizer composition to be brought into the form of aggregate bodies, e.g. pellets or granules, which are easily applied together with standard commercial fertilizers. As to the micronutrients in the fertilizer composition being readily soluble, it is believed that this results from the fact that in each individual aggregate body, the metal salts are intimately mixed with or in close proximity to the water-soluble nitrate. Thus, in the presence of water, e.g. in the soil or from direct precipitation, the micronutrient ions will be dissolved along with the nitrate ions, and the soil water will there¬ fore contain a relatively homogeneous mixture of, among other things, the micronutrient ions and nitrate ions. It is believed that the presence of the nitrate ions results in the micronutrients being in a form which is more readily accessible to the plants, perhaps by virtue of a reduced tendency to be adsorbed by soil particles, there¬ by ensuring a better absorption of the micronutrients. It is well- known that nitrate ions are readily absorbed by plants, and it has been shown during the testing of the fertilizer composition of the invention that the use of a greater amount of the water-soluble nitrate in the composition results in an increased yield.

As mentioned above, the formulation of the metal salts and the water- soluble nitrate together with a binder allows the fertilizer composi¬ tion to be brought into a form which is easily applied together with standard commercial fertilizers and which also is readily soluble in water. Any agriculturally acceptable material which is capable of binding the metal salts and the water-soluble nitrate together and which allows the metal salts and nitrate to be dissolved in water may be employed. Thus, the binder is preferably an agriculturally accep- table water-soluble organic binder, e.g. a plant product or a natural, semi-synthetic or synthetic polymer. Examples of suitable binders are those selected from the group consisting of plant pro¬ ducts such as wheat bran, wheat flour or sawdust; polysaccharides and polysaccharide derivatives such as starches, starch derivatives (e.g. Sta-Rx® 1500, Emdex® and Explotab®) , celluloses, microcrystal- line cellulose, cellulose derivatives, alginates, lactose, mannitol or sorbitol; proteins such as gelatins; gums such as acacia; and synthetic polymers such as polyethylene glycols (e.g. polyethylene glycol 4000 or 6000) or polyvinyl pyrrolidone. Another possible binder is calcium monohydrogen phosphate. It may furthermore be advantageous in certain cases to use a combination of binders.

The ratio between the amount of binder and the amount of the nutrient compounds (i.e. the metal salts and water-soluble nitrate(s) as well as any other nutrient compounds present) in the fertilizer composi- tion of the invention will of course vary according to the nature of the particular binder used, e.g. according to such factors as its binding ability and specific gravity, but it will generally be desir¬ able that the amount of the binder is kept to a minimum so as to keep the weight and bulk of the fertilizer composition to a minimum.

The term "aggregate bodies" refers to the fact that the fertilizer composition is in the form of individual units, each of which com¬ prises the metal salts mixed with or in contact with the water-solu¬ ble nitrate. The aggregate bodies may, for example, be in the form of pellets, granules and/or beads, or they may be in prilled form. The metal salts and the water-soluble nitrate are according to the pres- ent invention preferably intimately mixed within each individual aggregate body, whereby each aggregate body comprises a substantially homogeneous mixture containing particles of the metal salts and particles of the water-soluble nitrate(s). The term "particles" refers to particles which may have various sizes and shapes, for example, but not limited to, crystalline particles, granular par¬ ticles, powder or dust particles, etc. The individual aggregate bodies in which the metal salts and the water-soluble nitrate are intimately mixed may also be coated with any desired substance.

Typically, substantially all of the aggregate bodies will have at least one dimension of at least about 0.5 mm, and substantially all of the aggregate bodies will often have at least one dimension of at least about 1 mm. When the fertilizer composition of the invention is in the form of, e.g., pellets, substantially all of the aggregate bodies will typically have at least one dimension of at least about 3 mm.

The choice of the form and size of the individual aggregate bodies will depend upon such factors as the particular nutrient compounds and binders used as well as the form and size of the individual units of the macronutrient fertilizer with which the micronutrient ferti- lizer composition of the invention is to be applied. It will be obvious to a person skilled in the art that the size, shape and specific gravity of the aggregate bodies must be chosen so that the aggregate bodies of the micronutrient fertilizer composition are compatible with the individual units of any macronutrient fertilizer composition it is to be applied with, in order to ensure that a relatively homogeneous distribution of the micro- and macronutrient fertilizer compositions, respectively, may be obtained.

The aggregate bodies of the micronutrient fertilizer composition may be prepared using methods known in the art for the preparation of fertilizer compositions. For example, for the preparation of pellets, the composition may be prepared by first thoroughly mixing all of the micronutrient compounds and the water-soluble nitrate. The micro¬ nutrient-containing mixture is then mixed with the binder and, if necessary, with a limited amount of water or another liquid. Pellets may then formed from this mixture, e.g. using a standard pelleting machine for feed pellets. Essentially the same procedure may be followed for the preparation of, e.g., granules, with the exception that a machine for the preparation of granules is used instead of a pelleting machine. Similarly, other types of aggregate bodies, for example coated aggregate bodies, may be prepared by methods known in the art.

As mentioned above, another aspect of the invention relates to a solid fertilizer mixture comprising, as a first component, the above solid micronutrient fertilizer composition, and as a second compo- nent, a solid macronutrient fertilizer composition comprising at least N, P and/or K.

The macronutrient fertilizer component of the fertilizer mixture will typically be a standard commercial fertilizer, in particular a nitro¬ genous or N-P-K fertilizer. Such fertilizers typically comprise nitrogen in the form of urea, nitrate and/or ammonium, as well as varying amounts of P, K, Ca, Mg and/or S.

The macronutrient fertilizer component of the fertilizer mixture may also be an organic fertilizer.

As explained above, one of the advantages of the micronutrient ferti- lizer composition of the invention is that it may be applied to the soil or crops together with, e.g., standard commercial nitrogenous or N-P-K fertilizers. Therefore, it is desirable that the fertilizer mixture comprising the micronutrient fertilizer component and the macronutrient fertilizer component be formulated so as to allow for a uniform distribution of the micronutrient-containing component and the macronutrient-containing component upon application of the ferti¬ lizer to a crop or soil. This is achieved in practice by ensuring that the two components have a physical form, i.e. shape, size and specific gravity, which is compatible with each other. The individual units of the two components need not necessarily have exactly the same shape, size or specific gravity, but they should be formulated so that an approximately equal distribution of the two components of the mixture in the field may be achieved. The individual units of the components of the fertilizer mixture will therefore typically be in the form of pellets, granules and/or beads and/or in prilled form.

As mentioned above, the micronutrient fertilizer composition of the invention may in certain cases be applied alone, but will typically be applied together with a macronutrient fertilizer, i.e. in the form of the above fertilizer mixture.

In a further aspect, the present invention thus relates to a method for fertilizing crops using the above fertilizer mixture or the above micronutrient fertilizer composition.

As explained above, the amount of the micronutrient fertilizer compo¬ nent in the fertilizer mixture, or the amount of the micronutrient fertilizer composition, in the case of the micronutrient fertilizer composition being applied alone, which is to be applied to the soil in which crops are growing or are to be grown or which is to be applied to the plants must be chosen according to the quantities of the various nutrients in the fertilizer composition. The proper amount to be applied will be able to be determined in each particular case by a person skilled in the art. It is preferred that the micro¬ nutrient-containing fertilizer composition or the micronutrient fertilizer composition is applied relatively early in relation to the crop in question, as this has been shown to provide the best result.

Due to variations in soils, etc., it is difficult to provide precise amounts of the micronutrient fertilizer component in the fertilizer mixture or of the micronutrient fertilizer composition to be applied. However, in most cases, the micronutrient fertilizer component in the fertilizer mixture, or the micronutrient fertilizer composition, will be applied to the crops or to the soil In an amount of about 1-100 kg/ha, exclusive of any binder. Typically, the micronutrient ferti- lizer component in the fertilizer mixture, or the micronutrient fertilizer composition, is applied to the crops or to the soil in an amount of about 5-60 kg/ha, more typically in an amount of about 10- 40 kg/ha, exclusive of any binder. In a loam soil, It has been found that good results were obtained using an amount of about 10-35 kg/ha, and in particular In an amount of about 15-30 kg/ha.

The invention will be further illustrated by the following non-limi¬ ting examples.

EXAMPLE 1

A micronutrient fertilizer composition in the form of pellets com- prising the following components was prepared:

kg

Diammonlum phosphate 1.304

Potassium sulfate 1.304

Magnesium sulfate 7.391 Calcium nitrate 2.609

Sodium nitrate 1.304

Iron (II) sulfate 1.304

Copper sulfate 0.870

Copper oxychloride 0.870 Manganese sulfate 1.261

Solubor® 1.304

Zinc sulfate 0.435

Ammonium molybdate 0.044

Total 20.000

The composition was prepared by first thoroughly mixing all of the above ingredients manually using a shovel, after which the mixture, which had a dry, powdery consistency, was allowed to stand at ambient temperature and relative humidity for a period of about 1 1/2 months. The micronutrient-containing mixture, which then had a moist, sandy consistency, with the individual particles having a crystalline appearance (as seen under a magnifying glass), was then mixed with about 2 parts (by weight) wheat bran as a binder to about 13 parts (by weight) of the mixture. Pellets were then formed from this mix¬ ture using a standard pelleting machine for feed pellets. Steam was used during pressing in order to ensure the cohesiveness of the components of the pellets. The resulting pellets had a diameter of about 3.5 mm and a typical length of about 5-10 mm.

EXAMPLE 2

A micronutrient fertilizer composition was prepared as in Example 1. The composition comprised the following components:

kg

Diammonium phosphate 1.303

Potassium sulfate 1.303

Magnesium sulfate 7.383

Calcium nitrate 2.606 Sodium nitrate 1.303

Iron (II) sulfate 1.303

Copper sulfate 0.869

Copper oxychloride 0.869

Manganese sulfate 1.260 Solubor® 1.303

Zinc sulfate 0.434

Ammonium molybdate 0.044

Cobalt sulfate 0.022

Total 20.000

The nutrient content of the composition was as follows:

N 917 g

P 300 g K 534 g

Mg 728 g

Ca 606 g

Na 352 g S 1653 g

Fe 260 g

Cu 652 g

Mn 340 g

B 271 g Zn 95 g

Mo 21 g

Co 7 g

EXAMPLE 3

kg

Diammonium phosphate 1.235

Potassium sulfate 1.235

Magnesium sulfate 6.996 Calcium nitrate 2.469

Sodium nitrate 1.235

Iron (II) sulfate 1.235

Copper sulfate 0.823

Copper oxychloride 0.823 Manganese sulfate 1.193

Borax 2.284

Zinc sulfate 0.412

Ammonium molybdate 0.041

Cobalt sulfate 0.021

Total 20.002

The nutrient content of the composition was as follows:

N 866 g P 284 g

K 506 g

Mg 689 g

Ca 574 g Na 608 g

S 1636 g

Fe 247 g

Cu 616 g

Mn 322 g B 251 g

Zn 90 g

Mo 19 g

Co 7 g

EXAMPLE 4

A micronutrient fertilizer composition may be prepared as in Example 1 using the following components:

kg

Ammonium nitrate 2.000

Diammonium phosphate 1.235 Potassium nitrate 0.660

Potassium sulfate 0.610

Magnesium sulfate 7.000

Calcium nitrate 2.470

Sodium nitrate 2.000 Iron (II) sulfate 1.235

Copper sulfate 0.823

Copper oxychloride 0.823

Manganese sulfate 1.193

Borax 2.284 Solubor® 0.400

Zinc sulfate 1.235

Ammonium molybdate 0.041

Cobalt sulfate 0.021 Total 24.030

Such a composition comprises the following nutrients in the following amounts:

N 1771 g

P 288 g

K 501 g

Mg 690 g

Ca 568 g

Na 859 g

S 1608 g

Fe 247 g

Cu 616 g

Mn 322 g

B 334 g

Zn 272 g

Mo 5 g

Co 4 g

Cl 135 g

EXAMPLE 5

The effect of the micronutrient fertilizer compositions of the above examples on yields of winter wheat was determined.

The micronutrient fertilizer compositions were applied for several seasons in varying amounts to wheat grown in 100 m^ test plots (4x25 m) in a loam soil. The compositions applied were those of Example 2 (1987) and Example 3 (1988, 1989, and 1990). They were applied in amounts of 10, 15, 20, 25, 30, 35 and 40 kg/ha (exclusive of the binder) .

The micronutrient fertilizer compositions were applied along with standard fertilizer compositions containing N, P, K and Mg as de- scribed below, with plots fertilized with the standard fertilizer compositions but without the micronutrient fertilizer compositions serving as control plots.

In 1987 and 1988, nitrogenous fertilizer was applied in an amount of 300 kg N per hectare, 270 kg in the form of urea (46% N) and 30 kg as calcium ammonium nitrate (27.6% N) . In 1989, nitrogenous fertilizer was applied in the form of urea (270 kg N per hectare) and calcium nitrate (15% N, 30 kg/ha). The relatively large amount of nitrogen was applied in order to ensure that nitrogen was not the limiting factor for the growth of the plants.

The nitrogenous fertilizers were typically applied in 3 portions in February, May and June, respectively, with the calcium ammonium nitrate or calcium nitrate being applied in June. The micronutrient fertilizer compositions were applied in February together with the first portion of urea.

In 1990, 60 kg N/ha was applied in February as a mixture of diam¬ monium phosphate and calcium ammonium nitrate, together with the micronutrient fertilizer composition of Example 3. In April, 175 kg N/ha was applied as calcium ammonium nitrate.

In all 4 years, the crops were furthermore fertilized with 9 kg P/ha, 27 kg K/ha and 4 kg Mg/ha, the P, K and Mg being applied in February along with the micronutrient fertilizer composition and the first portion of nitrogen.

The time required for application of the micronutrient fertilizer composition together with the first portion of nitrogenous fertilizer was not significantly increased as compared to application of the nitrogenous fertilizer alone, since the micronutrient fertilizer composition in the form of pellets could be readily mixed and distri¬ buted with the nitrogenous fertilizer.

The following results (expressed as yield increase compared to the control plots, each number being an average for 4 plots, except for 1990) were obtained: Micronutrient-containing fertilizer composition applied (kg/ha) 10 15 20 25 30 35 40

Yield increase (hkg/ha)

2.24 4.36 6.47 - 0.49

4.26 2.99 1.72 2.62 3.51

6.37 11.2 5.34 2.79 5.64

6.03 3.11 1.82

Average 2.68 3.69 4.73 5.41 3.84 2.70 3.21

(* The numbers for 1990 are averages for the following number of plots: control, 3; 10 kg/ha, 7; 15 kg/ha, 8; 20 kg/ha, 6; 25 kg/ha, 6; 30 kg/ha, 7)

The average yield in the control plots was 94.09 hkg/ha, 97.06 hkg/ha, 103.22 hkg/ha and 111.32 hkg/ha, respectively, for 1987, 1988, 1989 and 1990, which gives an average of 101.42 hkg/ha for the four years.

It may be seen from the above table that the application of the micronutrient fertilizer compositions of the invention in an amount of from 10 to 40 kg/ha results in an increase in yield which is of a significant size compared to the average yield of the control plots.

Wheat samples from the plots which had received the micronutrient fertilizer compositions were analyzed for, among other things, ash content. It was found that the wheat had a relatively high ash con¬ tent in the dry matter (1.55%), indicating a high mineral content as a result of the absorption of the micronutrients in the micronutrient fertilizer composition of the invention. EXAMPLE 6

ANALYSIS OF WHEAT FERTILIZED WITH THE MICRONUTRIENT FERTILIZER COMPOSITION OF THE INVENTION

Winter wheat fertilized with the micronutrient fertilizer composition of Example 3 was analyzed for its content of a number of different nutrients. The results were compared with those of winter wheat which was grown under the same conditions, but which were not fertilized with the micronutrient fertilizer composition.

The wheat crop was fertilized with 230 kg N/ha, of which about 60 kg/ha was applied in February (i.e. at the beginning of the growth season) along with 9 kg P/ha, 27 kg K/ha and 20 kg/ha of the micro¬ nutrient fertilizer composition, the remainder of the N being applied at the end of April.

The results of nutrient analyses with and without the micronutrient fertilizer composition of the invention are shown in the following (in which "+ micro" represents the wheat to which the micronutrient fertilizer composition was applied and "- micro" represents a control crop fertilized as above but without the micronutrient fertilizer composition) :

Calculated nutrient content in the crop (pr. ha)

Nutrient + micro micro

N 341 kg 307 kg K 367 kg 356 kg P 47 kg 32 kg s 28 kg 24 kg

Ca 65 kg 38 kg

Mg 17 kg 13 kg

Fe 2687 g 3152 g

B 53 g 60 g

Mn 292 g 238 g

Zn 244 g 193 g

Cu 65 g 74 g

Na 874 g 1313 g

Si 32 kg 20 kg

It may be seen that the wheat which was fertilized with the micro¬ nutrient fertilizer composition of the invention contained an in- creased amount of a number of different nutrients. In particular, a substantially increased amount of nitrogen was absorbed as compared to the control crop. In addition to the improvement provided to the crop itself, this is an advantage from an environmental point of view, since the increased absorption of nitrogen will tend to reduce the amount of nitrate which may be leached out of the soil, thereby helping to reduce nitrate pollution of the ground water. EXAMPLE 7

FIELD TRIALS COMPARING THE MICRONUTRIENT FERTILIZER COMPOSITION OF THE INVENTION WITH OTHER MICRONUTRIENT-CONTAINING FERTILIZERS

The advantageous effect of the micronutrient fertilizer composition of the invention as compared to certain other commercial micronutri¬ ent-containing fertilizers was shown in field trials using winter wheat.

The following micronutrient fertilizer treatments were employed:

Amount used Name Nutrients in fertilizer (kg/ha)

* Micronutrient fertilizer composition according to the invention, corresponding to the composition of Example 3

The results of the field trials are given in the following table (the numbers being an average for 4 plots pr. treatment):

Yield increase compared to untreated

Treatment (hkg/ha) Relative yield

102 101 101 104 102 102 100

The average yield for the untreated plots was 94.8 hkg/ha.

It may be seen from the above table that the micronutrient fertilizer composition according to the invention provided a substantial yield increase not only compared to the untreated control, but also com¬ pared to the other micronutrient fertilizers tested. The micronutri¬ ent fertilizer composition of the invention ("øllingsøe Mikro") was the only micronutrient fertilizer tested which gave a statistically significant yield increase (95% level) compared to the control treat¬ ment.

Claims

1. A micronutrient fertilizer composition in the form of dry aggre¬ gate bodies, the fertilizer composition being adapted to be mixed with a macronutrient fertilizer composition, each aggregate body comprising salts of at least 2 metals selected from the group con¬ sisting of Cu in an amount of 300-15,000 g per 100 kg of the composi¬ tion, exclusive of any binder, Mn in an amount of 150-8000 g per 100 kg of the composition, exclusive of any binder, Zn in an amount of 50-4000 g per 100 kg of the composition, exclusive of any binder, Co in an amount of 1-200 g per 100 kg of the composition, exclusive of any binder, and Mo in an amount of 5-500 g per 100 kg of the composition, exclusive of any binder, as well as at least one water- soluble nitrate which is not in the form of a salt of the above- mentioned metals, the ratio between micronutrients and macronutrients In the micronutrient fertilizer composition being substantially above the ratio in which the micronutrients and macronutrients in question are required by crop plants.

2. A micronutrient fertilizer composition according to claim 1 which contains Cu in an amount of 1000-8000 g per 100 kg of the composi- tion, exclusive of any binder, Mn in an amount of 500-3000 g per

100 kg of the composition, exclusive of any binder, Zn in an amount of 150-2500 g per 100 kg of the composition, exclusive of any binder, Co in an amount of 5-100 g per 100 kg of the composition, exclusive of any binder, and/or Mo in an amount of 10-300 g per 100 kg of the composition, exclusive of any binder.

3. A micronutrient fertilizer composition according to claim 1 or 2 wherein each aggregate body contains an intimate mixture of parti¬ cles of the metal salts and particles of the nitrate.

4. A micronutrient fertilizer composition according to any one of claims 1-3 wherein each aggregate body further comprises at least one binder.

5. A micronutrient fertilizer composition according to any one of claims 1-4 wherein each aggregate body comprises salts of at least 3 of the metals.

6. A micronutrient fertilizer composition according to claim 5 wherein each aggregate body comprises salts of at least 4 of the metals.

7. A micronutrient fertilizer composition according to claim 6 wherein each aggregate body comprises salts of all 5 of the metals.

8. A micronutrient fertilizer composition according to any one of claims 1-7 which further comprises a boron-containing salt.

9. A micronutrient fertilizer composition according to any one of claims 1-8 wherein the metal salts comprise sulfates, nitrates and/or oxides.

10. A micronutrient fertilizer composition according to any one of claims 1-9 which comprises copper oxychloride.

11. A micronutrient fertilizer composition according to any one of claims 1-10 which comprises an iron salt.

12. A micronutrient fertilizer composition according to any one of claims 1-11 which comprises S, P, Mg, Ca and/or K.

13. A micronutrient fertilizer composition according to any one of claims 1-12 which comprises at least copper sulfate or copper oxy¬ chloride, manganese sulfate and zinc sulfate.

14. A micronutrient fertilizer composition according to any one of claims 1-13 which comprises at least one compound selected from the group consisting of iron sulfate, Solubor® (soluble sodium borate, Na2Bg0^3' ^0 , borax, ammonium molybdate, sodium molybdate and cobalt sulfate.

15. A micronutrient fertilizer composition according to any one of claims 1-14 wherein the water-soluble nitrate is selected from an alkali or alkaline earth metal nitrate and ammonium nitrate.

16. A micronutrient fertilizer composition according to claim 15 wherein the alkali or alkaline earth metal is selected from sodium, potassium and calcium.

17. A micronutrient fertilizer composition according to any one of claims 1-16 which comprises at least one compound selected from the group consisting of diammonium phosphate, potassium phosphate, potas- sium chloride, potassium sulfate and magnesium sulfate.

18. A solid fertilizer mixture comprising, as a first component, a solid micronutrient fertilizer composition according to any one of claims 1-17, and as a second component, a solid macronutrient fer¬ tilizer composition comprising at least N, P and/or K.

19. A fertilizer mixture according to claim 18 wherein the macro¬ nutrient fertilizer composition is a nitrogenous or N-P-K fertilizer.

20. A fertilizer mixture according to claim 18 or 19 wherein the macronutrient-containing component further comprises Ca, Mg and/or S.

21. A fertilizer mixture according to any one of claims 18-20 which is formulated so as to allow for a uniform distribution of the micro¬ nutrient-containing component and the macronutrient-containing com¬ ponent upon application of the fertilizer to a crop or soil.

22. A fertilizer mixture according to any one of claims 18-21 which is in the form of pellets, granules and/or beads and/or in prilled form.

23. A method for fertilizing crops, the method comprising applying to the crops or to the soil a micronutrient fertilizer composition according to any one of claims 1-17 or a fertilizer mixture accord¬ ing to any one of claims 18-22.

24. A method for preparing a micronutrient fertilizer composition in the form of dry aggregate bodies which are adapted to be mixed with a macronutrient fertilizer composition, the method comprising dry mixing without any substantial addition of water salts of at least 2 metals selected from the group consisting of Cu, Mn, Zn, Co and Mo as well as at least one water-soluble nitrate which is not in the form of a salt of said metals, said salts and said nitrate being in the form of powders, the ratio between said micronutrients and said macronutrients being substantially above the ratio in which said micronutrients and said macronutrients are required by crop plants, to obtain an intimately mixed micronutrient mixture, and mixing the resulting micronutrient mixture with a binder to obtain said micro¬ nutrient fertilizer composition in the form of dry aggregate bodies.

25. A method according to claim 24 wherein the micronutrient fertili- zer mixture contains Cu in an amount of 300-15,000 g per 100 kg of the composition, exclusive of any binder, Mn in an amount of 150- 8000 g per 100 kg of the composition, exclusive of any binder, Zn in an amount of 50-4000 g per 100 kg of the composition, exclusive of any binder, Co in an amount of 1-200 g per 100 kg of the composition, exclusive of any binder, and/or Mo in an amount of 5-500 g per 100 kg of the composition, exclusive of any binder.

26. A method according to claim 24 or 25 wherein said micronutrient mixture is allowed to stand, prior to mixing with the binder, until the consistency of said mixture has changed from a dry, powdery consistency to a moist, sandy consistency and until the Individual particles of said mixture have acquired a crystalline or crystal-like appearance.

27. A method according to any one of claims 24-26 wherein said salts and said nitrate are sieved and/or ground as necessary before mixing and/or after mixing.

28. A method according to any one of claims 24-27 wherein the micro¬ nutrient fertilizer composition is prepared using salts of at least 3 of the metals.

29. A method according to claim 28 wherein the micronutrient fertili¬ zer composition is prepared using salts of at least 4 of the metals.

30. A method according to claim 29 wherein the micronutrient fertili¬ zer composition is prepared using salts of all 5 of the metals.

31. A method according to any one of claims 24-30 wherein the micro¬ nutrient fertilizer composition in addition is prepared using a boron-containing salt.

32. A method according to any one of claims 24-31 wherein the metal salts comprise sulfates, nitrates and/or oxides.

33. A method according to any one of claims 24-32 wherein the micro¬ nutrient fertilizer composition is prepared using copper oxychloride.

34. A method according to any one of claims 24-33 wherein the micro¬ nutrient fertilizer composition in addition is prepared using an iron salt.

35. A method according to any one of claims 24-34 wherein the micro¬ nutrient fertilizer composition is prepared using S, P, Mg, Ca and/or K.

36. A method according to any one of claims 24-35 wherein the micro¬ nutrient fertilizer composition is prepared using at least copper sulf te or copper oxychloride, manganese sulfate and zinc sulfate.

37. A method according to any one of claims 24-36 wherein the micro¬ nutrient fertilizer composition is prepared using at least one com¬ pound selected from the group consisting of iron sulfate, Solubor® (soluble sodium borate,

, borax, ammonium molybdate, sodium molybdate and cobalt sulfate.

38. A method according to any one of claims 24-37 wherein the water- soluble nitrate is selected from an alkali or alkaline earth metal nitrate and ammonium nitrate.

39. A method according to claim 38 wherein the alkali or alkaline earth metal is selected from sodium, potassium and calcium.

40. A method according to any one of claims 24-39 wherein the micro¬ nutrient fertilizer composition is prepared using at least one com- pound selected from the group consisting of diammonium phosphate, potassium phosphate, potassium chloride, potassium sulfate and mag¬ nesium sulfate.

41. A method according to any one of claims 26-40 wherein said micro¬ nutrient mixture is allowed to stand, prior to mixing with the bin- der, for a period of at least about 2 weeks.

42. A method according to any one of claims 24-41 wherein the binder is an agriculturally acceptable water-soluble organic binder.

43. A method according to claim 42 wherein the binder is selected from the group consisting of plant products such as wheat bran, wheat flour or sawdust; polysaccharides and polysaccharide derivatives such as starches, starch derivatives, celluloses, microcrystalline cel¬ lulose, cellulose derivatives, alginates, lactose, mannitol or sor- bitol; proteins such as gelatins; gums such as acacia; and synthetic polymers such as polyethylene glycols or polyvinyl pyrrolidone.

44. A method according to any one of claims 24-43 wherein substan¬ tially all of the aggregate bodies have at least one dimension of at least about 0.5 mm.

45. A method according to any one of claims 24-44 wherein the ag¬ gregate bodies are formed as pellets, granules and/or beads and/or in prilled form.

46. A method according to claim 45 wherein the aggregate bodies are coated.

47. A micronutrient fertilizer composition in the form of dry ag¬ gregate bodies, the fertilizer composition being adapted to be mixed with a macronutrient fertilizer composition, each aggregate body comprising at least one salt of each metal in the group consisting of Cu, Mn, Zn, Co and Mo as well as at least one water-soluble nitrate which is not in the form of a salt of the above-mentioned metals, the ratio between micronutrients and macronutrients in the micronutrient fertilizer composition being substantially above the ratio in which the micronutrients and macronutrients in question are required by crop plants.