IMPROVEMENT OF SOIL MOISTURE RETENTION

Abstract: The process serves for the long-term improvement of soil moisture retention for the cultivation of plants (22) in a water-permeable, rapidly drying soil. A layer of cellulose absorption pads (10) containing a superabsorber and/or chips (14) acting as a moisture reservoir is introduced into a humus layer (16) or a layer of sand (18) below the usual working depth for cultivation. The pulps consist of complete, used absorption pads or absorption pads of manufacturing waste or chips (14) thereof. In addition to the usual horticultural and agricultural applications, the process allows for the urbanisation of soils in dry areas and in sandy and desert areas without any additional fixedly installed equipment.

Description: Improvement of soil moisture retention The invention relates to a process for the long-term improvement of soil moisture retention for the cultivation of plants in a water-permeable, rapidly drying soil, using a moisture reservoir below the usual working depth for cultivation, a moisture reservoir for carrying out the process and an application of the process. Previous experience has shown that there is no ground water present at low soil depths in water-permeable, rapidly drying soils. The agricultural, horticultural or forest cultivation of cultivated plants is therefore difficult to impossible without the use of irrigation systems which are expensive in all respects. In areas having soils of this kind, moreover, the generally sparse rainfall is usually concentrated. Extensive, heavy rainfall can occur at large intervals over a short period of time. A large proportion of the water seeps rapidly into the soil, evaporates or runs off. In this manner, no stable humus layer can be formed, the uppermost layer always being removed by wind erosion. If the ground water also present in deserts can be exploited, an artificial oasis is formed. The ground water is distributed in a uniform manner by means of ingenious, complicated irrigation systems and the plants are thus protected against withering. However, these irrigation systems are extremely expensive with respect to both capital investment and operating costs. Furthermore, the quantities of water falling on these plants are only absorbed to a small extent, the larger part seeping into the soil as already mentioned or evaporating very rapidly. Therefore, the quantities of water used at great expense are -2- only partly used, making the irrigation even more expensive. A further essential disadvantage of fixedly installed artificial irrigation systems consists in that substantial damage can occur in the event of a breakdown in operation, as plants used to a constant supply of water are only resistant for a short time or are not resistant at all and will wither. GB-A 2 048 635 describes a container of a water-tight material buried in the soil below the working depth, and covered with a water-permeable lid. A plant grows above the container, taking root in the direction of the container. In the event of rainfall, the water is collected in the container, instead of running off into a region that cannot be reached by the plant. The water collected diffuses into the root region of the plant in times of drought. CA-A 1 200 978 discloses a system of storage pockets and drainage holes for collecting water below the root region of plants. Pockets and holes are distributed over one same row and are graded between the rows. The system consists of plastic, and, for short-term experiments, also of cellulose products. The moisture collection according to GB-A-2 048 635 and CA-A-1 200 978 requires expensive systems. These costly systems are therefore probably only suitable for pots and small soil surfaces. The object of the invention is to provide a process of the type specified initially and to provide a moisture reservoir to carrying out the said process, which can be introduced and operated by simple means, is inexpensive to produce and maintains the weather resistance of the plants. With respect to the process, the problem is solved according to the invention in that at least one layer of cellulose absorption pads containing a superabsorber and/or chips thereof acting as a moisture reservoir is introduced into a humus or sand layer. Particular embodiments and developments of the invention form the subject of dependent claims. Many different absorption pads for water of all types are produced in large quantities. The fibre structure is also referred to as pulp. Absorption pads with a casing of cellulose fibres and an embedded superabsorber are particularly preferred. A superabsorber consists of high-absorption polymers which can absorb many times their own weight of water, thereby forming a gel which remains stable under the influence of normal pressure. The dimensional stability of an absorption pad can be increased further by adding a further fibre fluff of a thermoplastic material to the cellulose-containing fibre fluff, which acts as a hot-melt adhesive at points for the cellulose fibres at elevated temperatures. The thermoplastic fibres preferably consist of a polyolefin, e.g. polyethylene or polypropylene. If chips are to be produced from an absorption pad, dry absorption pads, which are also covered, are cut into pieces in a manner known per se, without any significant fibre separation. Chips, which are also pulps, can be transported in a simple manner as dry or dried bulk material. The dry or dried absorption pads in the form of used water- protection devices, used sanitary articles, manufacturing waste and/or chips of these articles are preferably introduced into the soil at a depth of 20 - 50 cm. The depth is selected according to the soil composition, the plants and the equipment used, which, during use, should not reach the layer of chips. On the other hand, however, the pulps serving as a moisture reservoir are only introduced at such a depth that the moisture can still reach the root region of the plants by diffusion processes and capillary action and does not have to cover too great a distance and lose its effectiveness. According to a first variant, the pulps (absorption pads and/or chips) are embedded individually, manually or mechanically. This is preferably effected in a single layer, the pulps being arranged alongside one another in a compact manner or, e.g. inversely proportional to the permeability of the soil, at a distance from one another. In the case of a highly permeable soil, the pulps are advantageously arranged in a compact manner or at a small distance from one another, and in the case of a less permeable soil, at a greater distance from one another. Although, in principle, the pulp could also be arranged in multiple layers, this is generally avoided in the case of absorption pads that have not been cut into pieces in view of the large water-absorption capacity of the pulp and the efficiency of the process. Loose, interspersed chips, on the other hand, can be arranged in multiple layers. According to a further variant of the invention, small absorption pads and/or chips can be inserted into an all-round water-permeable cover. This is the case when they are transported already in compact form rather than as bulk material. The covers with the inserted bulk material are preferably finely meshed nets or bags. The bulk material inserted into the covers is distributed in a uniform manner in the soil. Once they have been covered with humus and/or sand, the dry pulps inserted also absorb, in particular, the underlying soil moisture, this being possible by diffusion processes and capillary action. During the day, the moisture can diffuse into the root region of the plants, making up the deficits. The water running into the permeable soil in the event of rainfall is virtually completely absorbed by the pulps until saturation thereof, even when they are arranged at a distance from one another. If the necessary water is available, the inserted pulps transported in dry form are dampened thoroughly before they are covered with humus and/or sand, so that they can display their full effect from the outset and without rainfall. With respect to the moisture reservoir for carrying out the process, the problem is solved according to the invention in that it comprises superabsorber-containing cellulose absorption pads of manufacturing waste for the manufacture of sanitary articles and/or water-protection devices, dried used sanitary articles or used water-protection devices and/or chips of these products. According to the prior art, waste from the manufacture of napkins for infants and incontinent adults, bed liners, sanitary towels, panty liners and similar sanitary articles is often further processed at not inconsiderable costs. The same thing is true in the manufacture of water-protection devices in the form of bags, tubes and the like, sold, e.g. under the trade name SORBARIX by the company Ebiox System AG, CH-6204 Se pach. Instead of being further processed, the waste can also be used for soil moisture reservoirs. A further important source of pulps according to the invention consists in drying used water-protection devices and cutting them into pieces. The drying can be effected partially or completely in situ, the transport costs and loading being adapted economically and ecologically to the drying process. Water-protection devices contaminated with chemicals or the like are of course, as hitherto, taken for dumping or expert incineration. In certain cases, used sanitary articles can be cut into pieces ready for the process according to the invention if they are present in sufficient quantities in one place or can be advanced to a central chipping installation. The pulps introduced into the soil can absorb many times their own weight of water within a few seconds. This is particularly important in the event of heavy rainfall as the water cannot run down into the depths around the pulps. Therefore, e.g. a pulp of cellulose fibres with a superabsorbent material inserted in the usual quantity can absorb at least 50 times its own weight of water in approximately 5 seconds. By virtue of the high retention of the pulps, the moisture is not squeezed out of them, e.g. when the soil is worked by an agricultural vehicle. The process according to the invention can be used in all dry water-permeable soils, on an amateur or professional scale. However, it allows in particular for the urbanisation of soils in dry areas and sandy and desert areas without any additional fixedly installed equipment. The process is used to particular advantage in areas with heavy rainfall or with movable irrigation means that can only be used periodically. The latter irrigation methods occur, e.g. when moving over the soil with a pressure distributor. The combination of a watering arrangement with the invention is only conceivable in the case of extremely permeable soils. In particular, chips can also be scattered in plant tubs, seed beds, garden allotments and the like. The advantages of this invention can be summarised as follows: - urbanisation of soil which cannot be cultivated or can only be cultivated with difficulty at low cost - in general, no fixedly installed watering arrangements are necessary - rapid absorption and slow delivery of water by diffusion processes and capillary action - robust plants. Several embodiments of the invention, also the subject of dependent claims, will now be described in more detail with reference to the accompanying drawings, in which: ■ 8 - Fig. 1 is a schematic view of an absorption pad cut into chips, and Fig. 2 is a schematic vertical section through soil provided with chips. The portion of the cellulose absorption pad illustrated in Fig. 1, with an embedded superabsorber which cannot be seen, is waste material from a napkin manufacturing plant. The cellulose fibres are joined together at points by thermobonding with polyethylene fibrils, e.g. PULPLUS by DuPont. The pulp 10 is cut into chips 14 of a few centimetres in size, preferably l to 10 cm, illustrated by an arrow 12. These chips 14 form a bulk material that can be conveyed mechanically or pneumatically, and can be transported and stored in large containers, such as silo wagons. For reasons of cost, only manufacturing waste and dried, already used absorption pads which can covered in a water- permeable or partly water-permeable manner are used according to the invention. Absorption pads that are only partly water- permeable are preferably cut into pieces. Fig. 2 shows chips 14 introduced into the lower region of a humus layer 16. This layer is highly water-permeable and therefore itself displays no moisture retention. This also applies to the layer of sand 18 forming a gradual transition with the humus layer 16. The chips 14 are again arranged in the humus layer, although at a depth t which is greater than the working depth, e.g. the ploughing depth. This prevents the chips 14 reaching the surface 20 of the humus layer following working of the soil and losing their effectiveness. In the case of a relatively thin humus layer 16, the chips 14 can also be introduced into the layer of sand 18. Cultivated plants 22 can take root in the humus layer 16, and these roots 24 can push forward as far as the region of the chips 14. It can be seen easily that the chips 14 are arranged in multiple layers, again in a water-permeable cover. In addition, complete absorption pads can be inserted instead of chips 14, with or without a cover. Chips 14 or complete absorption pads have a favourable effect on the moisture regulation of the humus layer 16. They also absorb heavy rainfall, which is absorbed rapidly by the humus layer 16, which would otherwise run off via the layer of sand 18. As a result of diffusion processes and capillary action, the fibres of the roots 24 can absorb small quantities of moisture over a relatively long period. As a result of the sparing moisture supply, the cultivated plants 22 are used to a sparing water supply and can also withstand a long period of drought. The density of the chips 14 and/or absorption pads is varied according to the soil composition. The more permeable the soil, the more pulp is introduced. In the extreme case, the humus layer 16 is also a sand layer 18, i.e. it is virtually completely permeable.

Claims: CLAIMS 1. Process for the long-term improvement of soil moisture retention for the cultivation of plants (22) in a water- permeable, rapidly drying soil, using a moisture reservoir below the usual working depth for cultivation, characterised in that at least one layer of cellulose absorption pads (10) containing a superabsorber and/or chips (14) thereof acting as a moisture reservoir is introduced into a humus layer (16) or a layer of sand (18). 2. Process acording to claim 1, characterised in that the absorption pads (10) and/or chips (14) are introduced into the soil at a depth (t) of 20 to 50 cm. 3. Process according to claim 1 or claim 2, characterised in that the absorption pads (10) are introduced in the form of used water-protection devices, used sanitary articles, manufacturing waste and/or chips (14) of these products, individually, preferably in a single layer and arranged in a compact manner or at a distance from one another, distributed relative to one another according to the permeability of the soil. 4. Process according to claim 3, characterised in that small absorption pads (10) and/or chips (14) are inserted into an all-round water-permeable cover, preferably a net or a bag, and are distributed in a uniform manner therein. 5. Process according to one of claims 1 to 4, characterised in that the absorption pads (10) and/or chips (14) inserted are dampened before they are covered with humus and/or sand. 6. Moisture reservoir for carrying out the process according to one of claims l to 5, characterised in that it comprises superabsorber-containing cellulose absorption pads (10) of manufacturing waste for the manufacture of sanitary articles and/or water-protection devices, used sanitary articles or used water-protection devices and/or chips (14) of these products. 7. Moisture reservoir according to claim 6, characterised in that the chips (14) of absorption pads (10) are cut into pieces of a few centimetres in size, preferably 1 to 10 cm. 8. Moisture reservoir according to claim 6 or claim 7, characterised in that the absorption pads (10) and chips (14) absorb many times their own weight of water within a few seconds, preferably at least approximately fifty times their own weight. 9. Use of the process according to one of claims 1 to 5 for the urbanisation of soils in dry areas and sandy or desert areas without any additional fixedly installed equipment. 10. Use of the process according to claim 9 in areas with short, heavy showers of rain.

Inventors: LEONE DEMETRIO, LEONE, DEMETRIO
Applicants: LEONE DEMETRIO, LEONE, DEMETRIO
Application year: 1991
Main classification: C09K17
IPC codes: A01G1, A01G7, C09K17, C09K101