The present invention relates to a particulate fertilizer with neutralizing capacity and containing a balanced amount of nitrogen, potassium and liming agents and optionally other components for land cultivation uses and for the killing of moss.

For the cultivation of lands, including parks, garden areas and lawns, it will be advantageous to distribute only one single fertilizer supply a year whereby the most important plant nutrients, nitrogen, potassium and phosphorus and other minerals which are important to plant growth, are supplied to the plants and simultaneously supplying the liming agent necessary to maintain the soil pH (acidity) of the soil.

The supply of liming agent is most often carried out in the form of a separate liming operation with agricultural lime, i.e. crushed or comminuted dolomite lime, bryozo- and coral lime, white chalk, silty limestone, marl, etc. Such liming is typically carried out every four years, depending i.a. on the solubility of the liming agent supplied.

Liming is desirable as it renders the soil more porous and a number of nutrients become more readily obtainable for the plants. However, a high soil pH also increases the leaching of particularly nitrate ions to water streams, inshore waters and ground water. Moreover, there is an increased risk of percolation of humus. In the state of the art liming practice where the liming agent is typically supplied every four years there is a risk of the liming effect being too powerful immediately following the supply with ensuing leaching of e.g. phosphorus and nitrate. This recent knowledge has resulted in a significant reduction in the consumption of lime for agricultural purposes. In gardens and on park and lawn areas which constitute about 8,0% of all of Denmark, however, a general excessive liming continues to occur, since

the horticulturists are not organized in the same manner as the agriculturists which makes it difficult to find an adeguate information network. Moreover, the financial incentive to limit the costs involved in fertilizing and liming is less significant.

In connection with the cultivation and maintenance of cultivated lands, including gardens, park and lawn areas, it is advantageous to be able to supply the liming agent in balanced amounts adapted to the needs of the soil and the crop each year to avoid too large fluctuations in the soil soil pH. With the liming agents and fertilizers available, such practice entails a further distribution cycle with ensuing operations on site.

Dolomite lime is a preferred liming agent for agricultural and horticultural uses due to its high content of magnesium which is an important plant nutrient in addition to having soil neutralizing effect. O

II

Urea (NH ₂ CNH ₂ ) is marketed as a nitrogen fertilizer containing 46% of N in the form of amide nitrogen. Urea is readily so¬ luble and constitutes a readily available nutrient for plants, and prior to use it may be dissolved in water and sprayed onto the soil or the crop. Urea may furthermore be distributed in a solid state, e.g. as pellets or granules, directly onto the soil. However, urea is highly hygroscopic since it absorbs moisture from the environment. This renders urea fertilizers more susceptible to fluidisation and therefore they are less shelf stable than other solid fertilizers.

From US patent No. 3,684,476 it is known to produce a granular fertilizer containing N, Mg and Ca, wherein solid particulate urea is reacted in the absence of added water with selectively calcined (burnt) , solid, particulate

dolomite or dolomite limestone. The reaction occurs according to the following equations:

MgO + 2(NH ₂ ) ₂ -CO → MG(NH-CO-NH ₂ ) ₂ + H ₂ 0 og urea magnesium dicarbamide

MgO + (NH ₂ ) ₂ -CO → MG(NH) ₂ -CO + H ₂ 0 urea magnesium carbamide

The magnesium carbamides formed are sticky and the calcium carbonate, CaC0 ₃ , remaining from the selective calcination sticks to the magnesium carbamide particles to form a solid protective layer. The water formed in the reaction is to be eliminated to avoid the formation of Mg(OH) ₂ which may drive off NH ₃ from urea.

Thus, a non-hygroscopic inert fertilizer is obtained wherein nitrogen is protected against leaching and degassing and which may be stored and sown along with grain. Moreover, the fertilizer may be mixed with other fertilizers containing P, K and trace elements.

It is often recommended to fertilize and lime gardens and in particular lawns to combat undesired occurrence of moss which is becoming increasingly troublesome. Some of the reasons for moss occurrence are known and are generally considered to be a combination of a low soil pH in the soil, changes in the nutrient supply by precipitation and atmospheric deposition and removal of particularly potassium from the soil's reserves in connection with the removal of cuttings from lawns. However, usual fertilization and liming cannot entirely prevent moss growth. For actual moss removal it is recommended to spray or sprinkle iron or cupper sulfate which are highly poisonous to animals and humans, or to carry out mechanical raking. These methods are troublesome and often undesirable in gardens.

The supply of potassium fertilizer improves plant growth, in particular in lawn area where grass cuttings are removed. Potassium fertilizers are typically naturally occurring salts, such as sylvite, cainite, carnallite, etc., or synthetic salts, such as potassium sulphate, K ₂ SO _Λ , or potassium chloride, KCl, a low-density powder, which is very difficult to distribute by itself. Attempts to mix it with some other fertilizer will result in it separating off and most of it will flow away as dust. If the powder is slightly moistened to prevent dust formation, it will rapidly solidify and become useless. Moreover various potassium-containing powders are semi-products which are not marketed and there¬ fore they are not usually sold on a retail basis.

It is therefore the object of the invention to provide a fertilizer which is to be distributed on the cultivated areas only once a year and which contains a combination of liming agents and fertilizers. It is a further object to provide a fertilizer which simultaneously kills moss. The fertilizer should be stable and sprinkable. It is preferred that the fertilizer does not harden or form lumps during storage within normal shelf life.

This object is obtained with the fertilizer according to the present invention which is characterized in that it consists of from 10 to 60 percent by weight of a magnesium-containing liming agent, from 10 to 60 percent by weight of an amide compound, and from 10 to 30 percent by weight of a potassium compound and optionally additional components, such as trace elements, phosphorus and sulphur compounds, and other compo¬ nents and/or auxiliary agents in an amount of from 0 to 50 percent by weight, wherein the amide compound, the magnesium- containing liming agent and the potassium compound are combined completely or partially. The magnesium-containing liming agent is capable of bonding the amide and the potas¬ sium compounds in such a manner that the resulting mixture is

immediately sprinkable and stable across a wide moisture interval without further processing.

The fertilizer is preferably produced on the basis of a mixture of particulate, magnesium-containing liming agent, such as dolomite, dolomite limestone or magnesium limestone with varying moisture contents of from about 3 to about 14 percent by weight of water, preferably from about 5 to about 10 percent by weight of water, more preferably about 7 to 8 percent by weight of water, and particulate and substantially anhydrous urea, preferably a urea which contains 46% of N, a potassium compound, preferably a potassium salt, preferably potassium-sulfate (K ₂ S0 ₄ ) and from 0 to 50 percent by weight of additional fertilizer components.

Mixing of the particulate magnesium-containing liming agent with a natural moisture content and urea or a derivative thereof, such as formaldehyde-treated urea (sometimes referred to as "urea-form") produces a loss of heat in the mixture simultaneously with a certain amount of water separating off, which results in a slaking mixture. Whether a chemical reaction occurs and, in the affirmative, how it proceeds is uncertain. However, it may be assumed that, similarly to the reactions disclosed in US-A-3,684,476 between urea and selectively calcinated dolomite, i.e. the MgO-portion, bonding occurs of carbamide to magnesium which is present in the form of MgC0 ₃ in untreated dolomite and the like magnesium-containing minerals, resulting in the for¬ mation of H ₂ 0. The mixture thus produced is also very sticky thereby allowing bonding of added potassium sulphate or particulate, preferably powdered potassium chloride. At the same time the mixture becomes dry again or friable which means that it is sprinkable. One possible explanation of the apparent loss of water may be the absorption of free water in the potassium powder as hydrate water.

During subsequent normal storage of the fertilizer under pressure no lumping or NH ₃ -evaporation has been observed.

The invention further relates to a fertilizer of the above- mentioned type and having a moss killing effect and soil neutralizing capacity.

The invention further relates to a method for the production of the fertilizer according to the invention, said method being characterized in mixing particulate components compri¬ sing from 10 to 60 percent by weight of magnesium-containing liming agent, from 10 to 60 percent by weight of amide compound and from 10 to 30 percent by weight of particulate potassium salt and optionally additional fertilizer compo- nents, such as trace elements, phosphorus and sulphur compounds and/or auxiliary agents in an amount of up to 50 percent by weight in the absence of water whereby bonding between the components occurs which prevents them from separating during storage, handling and sprinkling. The desired product may be obtained independently of particular temperature conditions, e.g at a preferred temperature in the mixture of from 5* to 30"C. The conversion rate is increased by increasing temperatures. It is preferred that the particu¬ late components have a natural moisture or water content of from about 3 to about 14 percent by weight, preferably of from about 5 to about 10 percent by weight.

The following advantages are obtained with the fertilizer according to the invention:

a liming agent and fertilizer in one product which covers the total nutritive needs of the plants in a balanced ratio and minimization of the leaching of nutrients from the soil; - simultaneously non-toxic moss killing is achieved; a nitrate-free cover-all fertilizer may be combined with a varying N,P,K-ratio, e.g. 18-2-10 and 23-3-7,

preferably e.g. 14-4-10 which is recommended for most land cultivation uses, including gardens and parks, etc., and simultaneously having a soil neutralizing capacity of from 10 to 40%.

With a combined liming agent and fertilizer according to the invention having a neutralizing capacity of e.g. 25% and simultaneously having a high N,P,K-content, e.g. 14-4-10, it is possible in lawn areas and in gardens and in areas which are less intensively cultivated to distribute fertilizer only once a year using e.g. 40 kg fertilizer per 500m ² . For conventional gardening 50 kg of land cultivation lime per 500 m ² are typically used each year and 25-50 kg NPK fertilizer per 500 ² once or twice a year, which simultaneously has an acidifying effect on the soil.

By sprinkling of 40 kg per 500m ² of a fertilizer according to the invention with an N,P,K-content of e.g. 14-4-10 onto lawns with undesired moss growth, withering of the moss was observed already after three to four days. After nine weeks no regrowth of moss was observed. The distribution of conventional fertilizers and/or liming agents does not have this very quick and lasting effect. The moss killing effect may be due to a sticking of the smaller fertilizer particles, i.e. particles of less than about 0.1 mm, to the fertilizer which subsequently dies.

Table 1 shows different mixing ratios for the fertilizer according to the invention. The values are calculated and therefore no provisos are made for the diammonium (=diammo- nium phosphate) content "using" some of the neutralizing capacity.

Among other things, Table 2 shows that it is possible to compose a fertilizer according to the invention with an NPK- content of 25-3-10 and simultaneously maintaining a neutrali-

sing capacity of 14%. This is to be compared to known 25-3-9 NPK-fertilizers which have an acidifying effect.

Tabel 1

Different mixing ratios of fertilizer according to the invention which counteracts moss an _d has a neutralizing capacity.

Definitions:

"Magnesium-containing liming agent" as used herein means denotes a particulate product with a mesh size curve (par- tide size distribution) authorized for land cultivation uses, e.g. a product wherein 100 percent by weight of the particles are 4,0 mm or below, about 50 percent by weight thereof being 0,1 mm or below, and containing varying amounts of CaC0 ₃ , CaO, Ca(0H) ₂ , MgC0 ₃ , MgO and Mg(0H) ₂ and optional trace elements. The liming agent may thus be selected from among e.g. dolomite, dolomite limestone, magnesium limestone and combinations of calcium carbonate-containing minerals and products, such as bleaching chalk, bryozo lime, coral lime, white chalk, Thomas slag and precipitated calcium carbonate, and magnesium-containing minerals and products, such as kieserite, carnallite, epsomite and kainite, preferably MgC0 ₃ - or MgO-containing minerals and products. The liming agent is preferably untreated except from optional milling or grinding.

O

II

"Amide compound" means urea NH ₂ -C-NH ₂ and corresponding amide compounds and derivatives thereof, including urea-form (urea + formaldehyde or other aldehydes) and corresponding com¬ pounds which may be reacted with the magnesium-containing liming agent to obtain the fertilizer according to the invention.

"Potassium compounds" as used herein include all suitable, preferably neutral salts of potassium, such as potassium sulfate or potassium chloride, or K ₂ 0. Potassium sulfate is preferred since a sulphur component is obtained simultane¬ ously with this salt, and for garden uses a chlorine-poor fertilizer is preferred.

Further fertilizer components include in particular phos¬ phorus compounds, including raw phosphate, Thomas phosphate,

super phosphates, PK-fertilizers, nitrophosphates and ammonium phosphate, in particular diammonium phosphate which is also a nitrogen fertilizer. A content of up to 50 percent by weight is preferred, preferably of from 5 to 35 percent by weight, more preferably from 7.5 - 25 percent by weight of diammonium phosphate. Other fertilizer components further include all natural and synthetic, inorganic and organic com¬ pounds exhibiting fertilizing performance, including trace elements. In particular such trace elements include the elements Mn, Fe, Mo, B, Co, Cu, Zn and salts and complex compounds thereof.

Auxiliary agents include i.a. fillers, such as plaster.

Finally, the fertilizer may contain a nitrate compound in the form of e.g. calcium nitrate or calcium ammonium nitrate, if desirable. Generally, however, nitrate compounds are un¬ desirable and unnecessary in the fertilizer according to the invention which may be composed as a high-percentage nitrogen fertilizer with an N-content of up to 28 percent by weight, while entirely avoiding the use of nitrate.

"Moss killing" as used herein designates withering of moss characterized by an initial yellowing of the leafage followed by decay.

"Neutralizing capacity" as used herein means the calculated percentage of calcium carbonate on the basis of a chemical standard basicity determination of a weighed sample of the liming agent.

"Land cultivation uses" as used herein means every activity in connection with the cultivation and maintenance of agricultural, silvicultural, horticultural and park areas, including also private gardens as well as nurseries.

The fertilizer according to the invention has a preferred particle size distribution of from 0 to 3 mm in a balanced ratio so as to prevent it from separating. This may readily be obtained by the method according to the invention for producing the fertilizer.

The fertilizer may be distributed manually, but for large areas mechanical distribution is preferred, e.g. using a centrifugal spreader.

The fertilizer according to the invention may be used directly on all garden, grass and park areas and for all possible land cultivation uses. The fertilizer according to the invention may optionally be granulated for use in mechanical distribution.

Example 1

Production of fertilizer with the NPK-content of 14-4-10 (percentages) with 25% of neutralizing capacity. The follo¬ wing components were mixed:

500 g of dolomite (average water content 7-8%) 350 g of urea, pelleted (as urea form, available from Landbrugets Storkøb A/S, DK-

9260 Gistrup) 300 g of diammonium phosphate 350 g of potassium sulphate

at 15°C.

Following storage under pressure for six months at a tempera¬ ture of 15°C the fertilizer continues to be free-flowing. A moss killing effect is obtained after four to five days from sprinkling onto grass with undesired moss growth. The neutralising performance of the fertilizer was measured analytically to be 26%.

Example 2

Production of fertilizer with the NPK-content of 13-0-12: As in Example 1 but without diammonium phosphate. A calculated neutralizing capacity of 38% is obtained, cf. Table 1. Moss treated with the composition turned yellow after about 1 week. Following 1 month's storage like in Example 1, the fertilizer is still without lumps and free-flowing.

Example 3

Production of fertilizer with the NPK-content of 18-2-10 with a calculated neutralizing capacity of 29%. The following components were mixed:

10% of diammonium phosphate

23% of potassium sulphate

35% of urea, pelleted (as urea-form, available from Land- brugets Storkøb A/S, DK-9260 Gi- strup)

32% of dolomite

Moss killing effect corresponding to that of 14-4-10, cf. Example 1.