DE2127292A1 - Sil improvement using gypsum - in hydratable and settable form - Google Patents

Abstract

Use of hydratable and settable gypsum for improving soil structure. This form of gypsum imparts a friable texture to all kinds of soils, including sandy and very heavy clay soils. The hydratable gypsum may be any of the various kinds of gypsum produced by the partial or complete dehydration of gypsum (CaSO4.2H2O), e.g. Plaster of Paris, building gypsum or plastering gypsum, or a waste product from the chemical industry, esp. wet-process phosphoric acid prodn., opt. fully or partially dehydrated. Known setting retarders, e.g. glue, keratin, protein material, molasses or pref. liquid manure, or setting accelerators, e.g. K2SO4 and/or iron sulphate, may be added. The material may be applied (a) in the form of a suspension contg. 10-50%, pref. 25-35% gypsum, in which the gypsum may be replaced by soil in a ratio of 2:1-6:1 of soil to gypsum; or (b) in dry form when the soil is wet, followed by ploughing, harrowing, digging, etc., in which case the gypsum is mixed into the soil in a ratio of 1:20-1:4, pref. 1:10-1:5. Fertilisers may be applied at the same time, and seed may also be sown, opt. incorporated in the gypsum suspension.

Description

Methods and means for improving soil structure.

Agricultural tillage aims mainly at this starting to give the floor a crumbly structure gtrukXur. Just this quality enables the diverse reactions of chemical and biological nature in the soil and a slight penetration of the same, necessary for fertile plant growth required are. The crumb structure is also for a suitable water flow of great importance, e.g. rapid seepage during heavy downpours on the one hand. and, on the other hand, slower drying out in dry weather. It offers protection against twisting of the ground by wind (erosion).

Agriculture has many different means of improvement the structure of the soil, starting with the mechanical processing that has been known since ancient times through plowing and harrowing to biological methods that aim to get through To enable humus formation to crumble the soil in the first place. The use the various known means depends primarily on the type of soil, 5ei it is that it is a light sandy or a heavy clay soil. A remedy that has been known for centuries, the crumb structure especially of heavy ones Improving soils consists in giving the soil larger amounts of lime, usually in the form of of marl.

The known agricultural methods have in common that its effect on new territory unfolds only very slowly, so that it usually lasts for many years careful treatment is required in order to achieve sufficient fuel yields Soil quality (soil proof> to be achieved.

There was no shortage of boron tips, with the help of chemical additives to arrive at a suitable crumb structure in a faster way. Known The most important of these are the synthetic krilium preparations developed in the United States High polymers of the acrylonitrile type, which indeed needed an adequate effect, however, were far too expensive for more widespread use in agriculture.

The subject of the invention, however, is a very inexpensive means, whose excellent crumb-forming effect in the same way on very light sandy as well as very heavy clayey soils. It consists in the use of hydratable, i.e.

hardenable plaster of paris, It is true that gypsum has been used earlier, precisely at the beginning of the use of "artificial" fertilizers in agriculture, and its beneficial effect on the crumbling of heavy loamy soil is well known. The plaster of paris is has always been used in unfired form in its natural state as dihydrate or anhydrite, i.e. in a form that cannot be hydratably or only very slowly. Its fertilizing effect was based on the effect of calcium, which is an indispensable part of plant nutrition, and in special cases also on the fertilizing effect of sulphate ion. The well-known flocculating effect of the calcium ion on the colloids of the clay in the heavy soils has certainly also played a role. If a plaster of paris which is capable of setting is used according to the invention, then, in addition to the known beneficial effects of calcium and sulfate ions, there is also the bonding or cementing of the soil particles due to the setting of the plaster of paris. This makes it possible to achieve quick laying and crumb formation on a wide variety of soil types.

As hydratable plaster of paris for the purposes of the invention, all come in Gypsum industry produced by dehydrating ##### gypsum (calcium sulfate dihydrate) Types of plaster, such as plaster of paris, building plaster or plaster, screed plaster and the like., Into consideration. These are depending on the manufacturing method, # i.e. firing temperature, furnace type and Medium in which the drainage is done to quite a number of different Calcium sulphate modifications with reduced or no water of crystallization at all. So there is the very reactive / capable stucco plaster with setting times of 5 - 35 minutes essentially from ß- or α-hemihydrate (semihydrate), which does not stop more slowly Building plaster or plaster of paris, on the other hand, consists of a mixture of hemihydrate with a special active anhydrite modification. With advantage one will for the purposes of the invention use these reactive types of plaster. That doesn't mean it doesn't under certain circumstances, e.g. if the suspension to be sprayed is transported over long distances or when treating very extensive areas, also a less reactive one Type of plaster such as screed plaster can be used by burning at high temperature (800 - 1000) is obtained and as a result of the onset of decomposition, in addition to anhydrite contains certain amounts of calcium oxide.

When using d «g rapidly hydrating and consequently fast hardening stucco or plastering plaster can, if necessary, retarders known per se the setting time, such as glue, keratin, other silicon substances, molasses and the like will. The same goal can be achieved in agriculture with liquid manure or GAlleZ When using more slowly setting plaster, e.g. screed plaster, on the other hand, known accelerators can be added.

According to the invention one uses in this case with advantage substances that like potassium sulfate and / or iron sulfate, at the same time a fertilizing or soil-improving one Have an effect.

The application or type of application of the soil improver can be done and directed according to the invention in the most varied of ways depending on the type of soil as well as the planned cultivation.

For setting light dry sandy soils, in extreme cases e.g. from freshly washed up sand areas (reclamation) or even from sand dunes, you can put the plaster of paris in the form of a more or less fluid suspension on the Water, rain, spray or spray the soil. The gypsum content of the suspension can fluctuate within wide limits, e.g. from 10 - 50%. In most cases it will you can get by with 20-30%. The excess, not for hydrating the Gypsum required water seeps into the ground, and after a short time - within from 10-20 minutes when working without retarder - a solid top layer is formed.

This prevents, for example, and especially also prevents the floor from being accidentally missed rapid drying out.

For this type of laying down light soils one comes with amounts of 1 to 5 tons of gypsum per hectare. In many cases this plaster of paris requirement can be reduced considerably reduce or significantly strengthen the defined layer by adding the Suitable amounts of suspension soil: gypsum / soil, e.g. mixed in a ratio of 2: 1 to 6: 1.

In the case of very wet floors, on the other hand, it is advisable to apply the plaster preferably to apply in dry form and to use it with the soil in agriculture the usual way to mix by plowing, harrowing, tilling or cultivating. The effect just the hydratable gypsum according to the invention is already after a short time, e.g.

after one hour; Recognizable by the soil drying up. He loses its plastic properties and can be used if necessary Further Divide into smaller and more durable crumbs.

The amount of gypsum required for these heavy soils depends on on the type of soil, its water content, but also on the desired moisture content the crumb off. It is clear that this increases with increasing gypsum content that but crumbs that are too hard are also not desired. While in some cases yes a treated / gypsum addition to the floor of 1:20 shows a sufficient effect, In very watery soils, amounts up to a ratio of 1: 4 can be used. In general, gypsum additions of 1:10 to 1: 5 will be sufficient.

In order to save labor, the soil can be improved with plaster of paris according to the invention combine with other suitable work processes, e.g. with the introduction of Fertilizers. Since the plaster of paris is chemically neutral and not very soluble in water, can you mix it with all fertilizers and put it in solid or in suspension.

Exercises because of its neutral character and its poor solubility the gypsum does not have any adverse effect on seeds of any kind.

With great advantage you can therefore according to the invention the application of a Combine gypsum suspension on the ground with the seed by placing the seed in the suspension mixes in. This method is excellent for, for example the greening of new land, embankments, heaps etc. use. It has showed that e.g. grass seeds even consist of a thin layer of pure plaster of paris germinate undisturbed. The great advantage of this greening method is that that the seeds are not carried away by the wind or washed away by downpours. It also offers protection from bird damage.

Of course, the seed-gypsum suspension can still be ground Mix in as described above. This is recommended, for example very sterile heaps when greening, so that the fine roots germinate of the seed first find a substrate suitable for their development.

The use of Plaster of paris within the meaning of the invention for the accommodation and utilization of the huge The amount of gypsum generated as a by-product in the chemical industry. To point out in this context is particularly due to the many millions of tons of gypsum that are in large parts of the world in the "wet phosphoric acid production arise and their Storage or disposal encounters ever greater difficulties. This plaster of paris - in most cases it is a dihydrate - needed for the purposes of the invention only to be dehydrated to hemihydrate, for which all routes of the gypsum industry in this case it is advisable to use a particularly wet way by pressure boiling can be, reil the phosphoric acid gypsum is known to have a water content of 20-30 accrues. This possibility of utilization is not only for the densely populated; Industrial countries, like Germany, are important, but especially for the arid ones Climate zones of North Africa and the Middle East. Countries like Morocco, Algeria, Tunisia, Egypt, Israel and Jordan have significant phosphate deposits and also extensive phosphoric acid productions developing from it. Just in these countries, laying the ground and covering it with plaster of paris would be a delay drying out and preventing wind erosion are of considerable benefit.

The reuse of the phosphonic acid gypsum according to the invention brings the additional advantage that the residual phosphorsätlregehalt contained therein of 1-2 * P20s still contributes to the fertilizing effect.

Finally, it should be pointed out that there are various deviations of the wet phosphoric acid process, in which the plaster of paris is directly in the setting Form as hemihydrate is obtained.

This plaster of paris only needs to be dried for use according to the invention to become. With the appropriate location of the production facility, he could even #m without Drying in suspension, optionally with the addition of a retarder, directly on the surfaces to be treated are pumped.

Embodiment 1) Freshly washed up area is made by raining a suspension of 1 part of stucco in 2 parts of water in an amount of 4-5 t gypsum per hectare set. To avoid premature treatment of larger areas To prevent the gypsum from setting, the gypsum is suspended in manure.-It forms in a short time by hardening of the plaster in connection with the underlying Sand a firm 5-10 mm thick layer that prevents the land from drying out and Winddrift protects. - Before sowing the seeds, the layer is harrowed crumbled.

2) Light sandy soil can be fixed with a reduced amount of gypsum, by partially pushing the plaster of paris according to example 1), e.g. in a ratio of 3: 1, through the floor replaced. The water can then be added up to 1: 1 to parts by weight / 1: 1.5 solids Water can be reduced. - To save labor, you can use the suspension if necessary add a suitable complex fertilizer in an amount of 500 - 1000 kg / ha.

Examples described / 3) Those in the previous two / modes of operation can be combined with greenery by adding a a suitable grass seed mixture is added. 250-500 kg / ha of grass seeds are sufficient.

4) Fresh silt with a water content of 30-35% is used with 10-15% mixed with dry plaster. The mixture dries up in just 30-60 minutes and can then be easily #, e.g. by milling or cultivating, crumbly into a lookeren Break up the soil that can immediately serve as a seedbed #. The complete structural change e Bode can also be recognized by the foul smell of the @@ ch ing n @agen. Disappears.

to Sa @@, e.g. vegetables, develop a @iges @ first.

Claims (1)

Claims. 1. Use of hydratable and settable plaster of paris for improvement the soil structure. 2. The method according to claim 1, characterized in that the different in the gypsum industry through complete or partial dehydration of gypsum (calcium sulfate dihydrate ) types of plaster produced, preferably stucco and building plaster or plaster of paris, use Find. 7. The method according to claim 1 and 2, characterized in that the Gypsum well-known setting retarders, such as glue, keratin, proteins, molasses, preferably liquid manure or trTurle can be added. Method according to claim 1 and 2, characterized in that the Gypsum setting accelerators known per se, such as potassium sulphate and / or iron sulphate, 5. The method according to any one of claims 1-4, characterized in that that the gypsum on the ground in the form of a suspension with a gypsum content of 10-50%, preferably 25-35%. 6. The method according to claim 5, characterized in that the plaster of paris in the suspension partly through soil in a ratio of 2: 1 to 6: 1 soil to gypsum is replaced. 7. The method according to any one of claims 1-4, characterized in that that the plaster of paris sprinkled dry on the floor and with the treatment of wet floors according to this common practice in agriculture, such as plowing, harrowing, milling or cultivating. 8. The method according to claim 7, characterized in that the mixing of gypsum in the ground in proportions of 1:20 to 1: 4, preferably 1:10 to 1: 5, takes place. 9. The method according to any one of the preceding claims, characterized draws, fertilizers are introduced in the same operation. Method according to one of the preceding claims, characterized in that that in the same operation seed is incorporated io method according to one or several of claims 5, 6 and 1D, d -characterized in that the seeds of the gypsum suspension is admixed. 12. The method according to any one of the preceding claims, characterized indicates that waste gypsum from the chemical industry, preferably from phosphoric acid production, optionally after a total or partial dehydration, can be used. characterized / 13. The method according to claim 12, that phosphoric acid gypsum, which accrues directly as hemihydrate in Na @rfahren, as such in suspension or used in dried form.