Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Utility Patent
1998-11-12
2001-01-02
Dawson, Robert (Department: 1712)
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
C428S036920, C428S910000, C428S156000, C428S121000, C428S188000, C047S029500, C047S029500, C264S177170, C264S210700, C264S211120, C264S288400, C264S294000
Utility Patent
active
06168840
ABSTRACT:
The present invention relates to improvements relating to plant propagation techniques and specifically to means for encouraging the germination of plant seeds in cool climates.
In temperate climate zones, particularly in Europe, the British Isles, North America, Southern Australia and New Zealand germination of seeds is often delayed until the soil temperature has increased above its given minimum temperature determined by the nature of the seed and that the likelihood of frost has diminished. Furthermore it is desirable to improve moisture retention in the soil particularly in dry climates that occur in areas of Africa, Australia and the United States.
The present invention has reference to the propagation of a wide variety of plant seeds, however, specific description will be made with reference to the growing of maize corn crops, which represent a large proportion of cropping in temperate zones during the summer season.
Maize corn has a relatively long growing season of approximately 5 months before full maturity of the crop is reached.
This means that the seeds must be sown as soon as possible in the growing season to ensure maximum production of corn.
In many cool temperate zones, particularly in Europe, the growing season is relatively short and maybe shorter than that required to achieve full maturity of the corn harvest.
If the harvest does not reach full maturity this results in a reduced volume harvest and in some instances lower quality produce.
The present invention is primarily concerned with achieving earlier germination of seeds in a given growing season coupled with improving moisture retention in the soil during the growing phase of the crop.
Conventional methods of achieving this concern the use of thin plastic film layered on the cultivated soil, the soil having already been seeded or being seeded concurrently with the cultivation of the soil, or seeded at a later date through the plastic already laid after the plastic has had an opportunity to assist in the warming of the soil. Other methods include so called cloche cover film involving the use of film forming a tunnel like cover to protect growing plants.
In addition the film can be used in conventional greenhouse like structures or as a mulch film. In these instances the selective use of ultra violet ray stabilisation is desirable depending upon the purpose of the film and the desirability or not of quick break down of the film during the crop growth period.
For example in greenhouse use and mulch film use it is desirable that the file does not break down for the whole growing season, for example, in the cropping of strawberries or melon.
With conventional plastic cover techniques it is possible to cultivate the soil and apply the plastic film simultaneously with existing machinery. Such techniques allow the earlier germination of seeds and provide protection for the seedlings from late season frosts, but which will not impede growth of the seedlings beyond the initial germination stages.
The film maybe made from non-ultraviolet or ultraviolet resistant plastic and is extruded to a minimum thickness of between 10 to 15 microns. Cloche films maybe 10 to 25 microns and mulch films are conventionally 20 to 50 microns.
The use of UV resistant film is dictated to a certain extent by the use to which the film is to be put as mentioned previously. For example, to achieve fast degradation it may be necessary to use photodegradable and/or biodegradable additives.
Where it is desirable for quick degradation the use of relatively thick film does exhibit some practical problems in being slow to breakdown after germination of the seeds and furthermore, it has been shown that there is some difficulty in handling the film efficiently with machinery; finally use of the plastic at relatively high thicknesses is not always economically sensible.
With existing film extrusion machinery, it is not possible in practical procedures to extrude film having a thickness of less than about 8 microns.
The present invention has as its objective to provide a film for use in the covering of soil or greenhouse structures containing plant seeds or destined to contain seeds wherein, at least, some of the above mentioned problems are overcome.
According to the present invention there is provided a plastic film for covering seeded soil or soil destined to contain seeds for propagation, characterised in that the film is stretched at at least localised regions along a length of said film to beyond the yield point of the film to achieve a reduced thickness in said stretched region or regions whereby in use the film will deteriorate to allow passage of a germinated seedling therethrough.
In one preferred aspect the film may be completely stretched beyond its yield point. Alternatively the film may be stretched beyond its yield point along one or more lines along the length of the film. Conveniently, the film may be stretched beyond its yield point in a predetermined pattern of said localised regions along a length of said film. In another arrangement, the film may be completely stretched beyond its yield point and is thereafter further stretched along one or more lines along the length of the film. In a still further possible arrangement, the film may be completely stretched beyond its yield point and is thereafter further stretched in a predetermined pattern of said localised regions along a length of said film.
The film is preferably stretched at its point of extrusion, that is, in line stretching of the film during the extrusion process.
The film may be stretched at a secondary out of line stretching process. Alternatively the film may be stretched at the point of application of the film to the soil and this latter method will be described in greater detail in the practical arrangement. Stretching at the point of extrusion (in-line stretching) and/or stretching during a secondary process before working in the field will be the preferred option to reduce the likelihood of damage to the film at the point of laying the film onto a crop bed.
In a further aspect of the invention, there is provided a film for use in the covering of soil containing plant seeds or destined to contain plant seeds to be germinated in which a non-ultraviolet resistant (photodegradable) biologically degradable film web has undergone stretching beyond its yield point whereby the thickness of the film is reduced to a thickness of 10 microns or less such that at least part of the web will more quickly deteriorate through weathering and or biological activity and thereby allow passage of a germinated seedling from beneath the protective cover of the film which has acted to facilitate heating of the soil and protection from frosts during the seed germination process and/or preceding period.
Optionally the film may be untreated, photodegradable, biodegradable or a combination of the above. In some instances as mentioned previously the film should be photodegradable to allow acceleration of UV degradation and allows the germinated crop to emerge after the initial growing stage after a relatively short time span of say one month. Opaque film may be used to restrict passage of light to the area of soil surrounding a plant. Additional localised stretching of the film renders the film transparent in local sections near the plant to allow light to pass through.
The stretching of the film is achieved by a plastic film stretching machine and such machines are well known in this field.
In one aspect of the invention, edges of the film may be folded or of greater thickness than the mid portion of the film to enable more efficient machine handling and anchoring of the film during laying thereof onto the ground and covering of the film at least on the edge portions by soil.
The film is preferably pre-stretched prior to the application of the film onto the ground and the film may be stored in its stretched condition on rolls ready for use. Additional stretching of the film by the formation of spaced dimples along the length of the film may be provided with the dimples providing space for
Alston & Bird LLP
Dawson Robert
First Green Park PTY LTD
Peng Kuo-Liang
LandOfFree
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