GB2428239A

GB2428239A - Improved agricultural lime

Info

Publication number: GB2428239A
Application number: GB0426405A
Authority: GB
Inventors: John William Carson
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-12-02
Filing date: 2004-12-02
Publication date: 2007-01-24
Anticipated expiration: 2024-12-02
Also published as: GB2428239B; GB0426405D0

Abstract

An improved agricultural lime composition comprises, in combination, alkali earth carbonates, alkali earth sulphates and metal oxide hydrogels. The alkali earth sulphates may be made in situ by the addition of sulphuric acid to the carbonate. The improved lime may also contain primary, secondary and trace nutrients, crop seeds and agrochemicals. Industrial waste product may be used in the manufacture of the improved lime. The physico chemical nature of the improved lime confers extended release properties on the active ingredients involved.

Description

IMPROVED AGRICULTURAL LIMING

The present invention relates to improvements to the chemical and physical properties of agricultural lime, its agronomic value, its economics in use and its environmental impact.

Agricultural liming is defined herein as the established farming practice of applying finely "1 ground limestone, magnesium limestone, chalk, or alkaline by products or waste products or crushed sea shells to land to be cultivated or to soils in which crops are to be grown.

Many types of soils used for agronomic purposes became increasingly acidic over time. This increasing acidity is caused by a range of inter- related functions in the soil, which may include; parts of the crop rotting, micro organism activity, acidic rainfall or irrigation, the fertilisers used or the limited ability of the soil to buffer the changes in pH.

Buffering is herein defined as the control of soil pH to a figure close to 7 on the pH scale.

Buffering is a known effect which can be bought about by the presence in soils of salts comprised of strong alkalis and weak organic acids.

The yields from the cultivation or farming of many kinds of crops are adversely affected by increasing soil acidity, which is to say decreasing soil pH. The technique of agricultural liming is therefore practiced widely in attempts to improve crop yields. The purpose of the conventional form of agricultural liming is to counteract increases in soil acidity by neutralising it with strong alkali. For this purpose available material such minerals are used in finely divided form wherein they act as strong calcium and or magnesium alkalis. 2.

The result of conventional agricultural liming is that soil pH is increased sharply, that is abruptly. The alkali firstly neutralises the soil acids and then immediately besifies the soil. By basify it is herein defined as making the soil basic which is to say alkaline, that is with a pH significantly greater than 7.

Because soil pH is difficult to control accurately there is a tendency in conventional agricultural liming to add excess alkali. This excess agricultural lime may be expected to be gradually neutralised by soil acids as time passes. However, while this may eventually occur there are important adverse side effects, in the soil, which should be considered.

The first adverse side effect is that many crops ideally prefer a soil pH which is close to 7 rather than significantly alkaline as is produced by excessive use of conventional agricultural lime.

The second adverse side effect is that most fertilisers provide their nitrogen, which is one of three primary crops nutrients, at least partly in the form of ammonium salts. Ammonium salts are decomposed by alkaline soils into gaseous ammonia which escapes from the soils into the atmosphere and is therefore of no value to the crops.

The third side effects is damage to the structure of the soil. Soil is a complex natural substance which supports a multiplicity of life forms, both plants and micro organisms. A vital feature of healthy soils, which is to say soils which support healthy life, is their colloidal structure.

A colloidal structure is herein defined as a substance composed of fine solid particles dispersed in a fluid. In the specific case of soil colloids the structure is composed of fine inorganic and organic solid particles, dispersed in a fluid phase based on water but containing dissolved inorganic and organic substances and including gasses as part of this fluid phase. 3.

It is from this colloidal structure that the multiplicity of life forms, including crops which are present in healthy soils, obtain their sustenance, Any damage to the colloidal structure of soil can impair crop growth. Sudden significant changes in soil pH, for example from an acidic state to an alkaline state are known to disrupt soil colloids. The result is that the soils become more friable, they retain less water dissolved substances and gasses and in extreme cases they become prone to erosion both by water and wind.

From an agronomic point of view conventional agricultural liming can be seen to cause the three important adverse side effects described above. Conventional agricultural liming can also be seen as economically inefficient because it necessitates a specific application to land, that is in addition to the necessary addition of seed and fertilisers to the land.

It has been the aim of my research to eradicate these adverse agronomic and economic effects of conventional agricultural liming. It has now been discovered according to the present invention that an agronomically effective and economically efficient alternative to conventional agricultural liming can be produced and applied. This novel product is known herein as improved agricultural lime.

The invention described herein, namely improved agricultural lime, provides for the manufacture of a new form of agricultural lime which both controls soil acidity and provides nutrification and may also carry the seed of the crop and also selected agrichemicals.

This is to say that the standard form of the improved agricultural lime described herein is a combination of a soil pH modifying agent and a provider of fertiliser. To this combination may also be added the crop seeds and agrichemicals. Using this novel approach farmers need only make one, rather than two or more, applications to their land each growing season. 4.

The basis of the present invention is that a combination of inorganic and or mineral substances can be used to produce the standard form of improved agricultural lime, which reacts in the soil to bring about both pH control and provide nutrification for the cultivation of healthy crops.

Moreover this novel composition of matter known herein as the standard form of improved agricultural lime, can be made to include ranges of industrial by products, which significantly reduces the overall costs incurred in producing this improved agricultural lime. Essentially there are three ingredients used in the manufacture of the standard form of improved agricultural lime and these will be described in the following paragraphs. It should be noted however that other ingredients can also be added to the improved agricultural lime described herein.

The first ingredient that this invention involves is a source of alkali earth carbonate. Many sources of alkali earth carbonate exist in nature as rocks or minerals or sea shells. Other sources arise as industrial wastes. Any type of alkali earth carbonate or mixed alkali earth carbonate that is or could be used as conventional agricultural lime can be used as the main ingredient of improved agricultural lime.

The second ingredient that this invention involves is a source of sulphuric acid. The source may be prime quality sulphuric acid, however many sources of by product sulphuric acid arises within the industries of most industrialised nations. Any type of by product sulphuric acid such as those arising from mineral or ore treatment or metal manufacture can be used, except in cases where phyto toxic pollutants are present in the by product. Many waste stream sulphuric acids can be used, derived from manufacturing industry, which contain considerable quantities of dissolved metals such as iron and trace quantities of other metals. The presence of both iron and these trace metals are beneficial as ingredients of improved agricultural lime. 5.

The third ingredient that this invention involves is a source of the three primary plant nutrients; nitrogen, phosphorus and potassium. Many sources of each of these elements are known both as minerals such as sodium nitrate and potassium chloride and as processed minerals such as super phosphates. Additionally industrial by products such as waste phosphoric acid and waste nitric acid can be used. It should be noted however that neither ammonia solutions or ammonium salt compounds are suitable as nitrogen sources in improved agricultural lime. Essentially there are three stages in the manufacture of the standard form of improved agricultural lime and these will be described in the following paragraphs.

The first stage in the manufacture of improved agricultural lime is the comminution, that is grinding, of the alkali earth carbonate to a fine powder. This first stage in the process is exactly the same as is used in the manufacture of conventional agricultural lime. This can be convenientiy achieved at the quarry using conventional crushing and grinding plant.

The second stage in the manufacture of improved agricultural lime is the addition of the sulphuric acid ingredient to the ground alkali earth carbonate. This may either be carried out at the quarry or at the industrial manufacturing facility where the by product sulphuric acid arises. This blending process can be conveniently achieved by spraying the sulphuric acid onto the ground alkali earth carbonate held in a rotating mixer. Alternatively this blending process may be part of the industrial process which generates the sulphuric acid waste, for example a neutralisation and filtration process. Carbon dioxide is given off in this process as is small quantities of sulphuric acid mist. These by products of the reaction need to be removed from the atmosphere by scrubbing.

The result of the first two stages in the manufacture of improved agricultural lime is a damp solid the grains of which have cores of alkali earth carbonate and coatings of hydrated calcium sulphate and metal hydroxides such as iron hydroxide. 6.

This damp solid is then treated via the third stage in the manufacturing process to produce the standard form of the improved agricultural lime product. The third stage involves the dissolving or the suspending of the nitrogen, phosphorus and potassium raw materials, that is to say the primary plant nutrients, in water or sulphuric acid.

This nutrient mix is then added to the damp solid. This can again be conveniently achieved either at the quarry or the industrial site at which the by product sulphuric acid arises.

The addition may be made by stirring or spraying the nutrient mix into the damp solid.

The mixture which results from the third stage of the manufacturing process, described above, is the standard form of the improved agricultural lime product.

The nature of the standard form of the improved agricultural lime product will now be described.

Physically the standard form of the improved agricultural lime product is a moist but free flowing granular solid with a fine grain size. As such it is suitable for spreading on agricultural land using conventional agricultural lime spreaders.

The structure of the grains of the standard form of the improved agricultural lime product is that each grain has a solid core of unreacted alkali earth carbonate which is surrounded by a hydrogel structure composed of hydrated calcium sulphate together with hydroxides of metals such as iron, onto which is adsorbed primary plant nutrients.

A hydrogel is herein defined as a gelatinous or colloidal ultra fine precipitate. Such structures are know to adsorbe ions such as nitrates, phosphates and potassium. 7.

The range of chemical analyses of the standard form of the improved agricultural lime is as follows, on a dry weight basis; Alkali earth carbonates (eg as Ca C03J 40% to 80% Hydrated alkali earth sulphate [eg as Ca C03 2H20) 5% to 40% Nitrogen (as N) 1%to 10% Phosphorus (as P205) 1% to 1 0% Potassium (as K20) 1% to 10% Hydrated metal hydrogels (eg as Fe (OH)3) 1% to 20% The physical and chemical effects of the standard form of the improved agricultural lime will now be described.

Upon spreading onto and ploughing into soils the improved agricultural lime is irrigated by acidic soil waters. These partially displace the hyrogel coating and start to release the plant nutrients which are taken into the colloid structure of the soil.

The hydrated calcium sulphate has a finite solubility in soil waters and it too is taken into the colloid structure of the soils. Here it reacts slowly with soil acids, to form calcium salts of organic acids which act as buffering agents.

These buffering agents, the calcium salts of acids such as oxalic acid and humic acid, maintain soil pH close to the optimum of pH7.

The colloidal structure of the soil adsorbs primary, secondary and trace nutrients and buffering agents. Once absorbed these and other active ingredients are slowly released in a controlled, that is extended manor. Once released these active ingredients can be taken up bythe crop. 8.

The core of the improved agricultural lime dissolves slowly releasing alkali earth salts.

However, because of the presence in the soil of the buffering agents excessive alkali and the onset of basification is avoided.

The chemical structure of improved agricultural lime, as described herein, and as applied in its standard form by spreading and ploughing into agricultural land, is believed to be a unique composition of matter, namely a partially sulphated alkali earth carbonate incorporating a nutrified hydrogel.

The agronomic and economic advantages of modified agricultural lime will now be defined.

Improved agricultural lime is advantageous to farmers because it provides a method by which land used for agronomic purposes can be conveniently nutrified and de-acidified via a single application, rather than using conventional agricultural liming followed by the separate application of fertiliser. This single application method has cbvious economic advantages over conventional land management practice.

Agronomically, improved agricultural lime is advantageous because it provides all the active ingredients required for healthy crops, in terms of pH regulation and nutrification, without causing damage to the soil colloidal structure. Moreover both pH regulating and nutrifying active ingredients are held in physico chemical forms which extend their release. This is a controlled release effect which in turn facilitates improved plant nutrient uptake and the opportunity to use less of the active ingredients, per annual application, than would be the case with conventional land management practice.

This controlled release effect also reduces the loss of agricultural active ingredients into surface waters where they would otherwise cause pollution. 9.

Environmentally, improved agricultural lime is advantageous because it utilises industrial waste streams, which could otherwise become pollutants, and because it obviates the dust cloud problem that can occur through use of dry conventional agricultural lime. Moreover, the controlled release effect achieved means that a higher percentage of nutrients are taken up by the crop, which in turn means that a lower percentage of nutrients are washed out of the soil. The loss of fertiliser nutrients from soil and into streams and rivers is recognised as a problematic form of environmental pollution. The use of improved agricultural lime considerably reduces this pollution hazard.

Taken together this novel composition of matter with its attendant economic, agronomic and environmental advantages constitutes a major advance over conventional land management practice.

As such this invention has major potential in many branches of agriculture throughout industrialised countries.

A typical formula for the standard form of improved agricultural lime, on a dry weight basis, is as follows.

Calcium carbonate (as Ca 0J3 derived from chalk or limestone) 35% Hydrated calcium sulphate (as C6SO42H2O derived from waste H2S04) 15% Nitrogen (as N derived from nitrates in the nutrient mix) 10% Phosphorous (as P205 derived from phosphates in the nutrient mix) 5% Potassium (as 1<20 derived from potassium salts in the nutrient mix) 5% Hydrated iron hydroxide (as Fe(OH)3 derived form waste H2S04) 10% In addition to the above standard form of improved agricultural lime, research has shown that the following variations are also useful. 10.

The standarci form of improved agricultural lime, as defined above is a moist granular solid intended to be applied to agronomic land by conventional spreaders and ploughs. A variation can be manufactured which contain added water so that the improved agricultural lime becomes a slurry which can then be applied to land or soils by spraying. This variant of improved agricultural lime is especially appropriate in horticultural applications.

The standard form of improved agricultural lime may be varied so as to supply different ratios of nutrients, Thus for example the addition of sources of the three nutrients to the nutrient mix may be varied as follows: The ratio of nitrogen to phosphorus to potassium many be varied for example to produce 5% N 5% P205 10% 1<20 or 5% N I 0% P205 5% 1(20 or 7%N 7%P205 7%K20 There are many such possible ratio variations to suit specific crops and soils.

Alternatively potassium and phosphorus can be excluded to produce a nitrogen only fertiliser.

It is also possible to provide both ranges of primary and secondly nutrients in variants of improved agriculture lime. It should be noted that the following three secondary elements are provided in the standard form; calcium, sulphur and iron. To these may be added magnesium, for example via the addition of dolomite powder, as the fourth secondary nutrient It is also possible to provide additional trace elements in variations of improved agricultural lime. It should be noted that many valuable trace elements are provided in the standard form, derived from sulphuric acid waste streams. To these may be added for example boron, cobalt, copper, manganese and vanadium plus any other specific trace elements needed by a particular crop. 11.

Also, it is possible to omit the addition of the nutrient mix entirely and thereby produce a form of un nutrifed improved agricultural lime.

It is also possible to add crop seeds to versions of improved agricultural lime. Seeds such as grasses and or meadow flowers or cereals or vegetables, for example, can be added either as coated seeds or uncoated.

It is also possible to add crop protecting agrichemicals to versions of improved agricultural lime. Agrichemicals such as biocides, herbicides, fungicides and or growth stimulants for example can be added either as coated granules or pellets or, in some cases, uncoated.

All of the features disclosed in this specification, and or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of the features and or steps are mutually exclusive.

Each feature disclosed in this specification may be replaced by alternative features serving the same purpose. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification, or to any novel combination of the steps of any method or process so disclosed. 12.

Claims

1. An improved agricultural lime comprising in combination (a) alkali earth carbonates (b] hydrated alkali earth suiphates (c] metal oxide hydrogels.

2. An improved agricultural lime according to claim 1, wherein the proportions on a dry weight basis of the components are: (a) Alkali earth carbonates 40% - 80% [b) Hydrated alkali metal sulphates 5% - 40% [c) Metal oxide hydrogels 1% - 20%

3. An improved agricultural lime according to claim 2, wherein components [a), (b) and (c) together comprise 50 to 1 O0% on a dry weight basis of the agricultural liming agent.

4. An improved agricultural lime according to claim 1, 2 and 3 which also contains any or all of the three primary plant growth nutrients namely sources of nitrogen, phosphorus and potassium.

5. An improved agricultural lime according to claims 1, 2 and 3 which also contains any or all of the four secondary plant growth nutrients namely calcium, magnesium, sulphur and iron.

6. An improved agricultural lime according to claims 1, 2 and 3 which also contain any or all of the trace elements needed for healthy plant growth for example boron, cobalt, copper, manganese and vanadium. 13.

7. An improved agricultural lime according to claims 1, 2 and 3 which also contains crop seeds for example grasses, meadow flowers, cereals or vegetables.

8. An improved agricultural lime according to claims 1, 2 and 3 which also contains agrochemicals such as biocides, herbicides, fungicides and or growth nutrients.

9. An improved agricultural lime according to claims 1, 2 and 3 which contains any combination or all or some or none of the additional components exemplified in claims 4 to 8.

10. An method for the agronomic improvement of land by use of en improved agricultural lime as claimed in any preceding claim.

11. A method for the agronomic improvement of land according to claim 10 wherein some of the components are derived from industrial wastes.

12. A method for the agronomic improvement of land according to claim 10 wherein the improved agricultural lime is applied to the surface of the land as a moist powder or a granule or a slurry and then ploughed into the soil.

13. An improved agricultural lime substantially as described herein.

14. A method for the agronomic improvement of land substantially as described herein.