Planting – Plant setting – Through mulch
Reexamination Certificate
1998-01-13
2001-02-20
Batson, Victor (Department: 3671)
Planting
Plant setting
Through mulch
C111S900000, C111S200000, C047S009000
Reexamination Certificate
active
06189466
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to weed control by means of soil coverage with plastics film and, particularly, control of nutsedge (Cyperus spp) by said means.
BACKGROUND TO THE INVENTION
Soil solarization is a hydrothermal process that utilizes the sun's energy to heat moist soil that is mulched under polyethylene. The basic concept of soil solarization is to use clear plastic films to allow transmission of light energy to the soil, where it is absorbed and used to heat the soil. The clear plastic film decreases convective heat loss so that increased soil temperatures are achieved. If the temperature under the plastic film and in the soil reaches sufficiently high temperatures, weeds and other plant pests are damaged or killed. Consequently, the need for chemical pesticides, or the amount of pesticide, is decreased by using soil solarization. Accordingly, in arid cloud-free regions, the soil solarization technique has found wide application for the control of some soil-borne diseases and weeds.
Thus, in high light, cloud-free climates soil solarization with clear polyethylene films has been used successfully. However, in more humid environments, where clouds are a common occurrence, soil solarization is of less value in not providing the desired temperature. Further, one of the large losses of energy from the soil during solariation is as thermal-infrared radiation from the soil back through the film.
Thus, under a consistent cloudy environment, prior art soil solarization methods are less efficacious, particularly against certain noxious weeds, such as yellow and purple nutsedge (Cyperus spp). There is, therefore, a need for an improved method of weed control involving a more efficacious solarization technique and/or plastics film of use therein.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved soil solarization method that uses a thermal-infrared absorbing film for the control of noxious weeds, particularly, nutsedge.
It is a further object of the invention to provide an improved field management method for the control of noxious weeds.
Soil solarization involves the laying of a film of a suitable plastics material on soil to be heated by solar radiation for insect, pathogen and weed control prior to the transplanting of a fruit or vegetable cash crop in the soil.
Accordingly, in one aspect the invention provides a method of controlling noxious weeds by soil solarization of soil, said method comprising covering said soil with an effective thickness of a transparent, thermoplastic IR retentive film for a sufficient period of time to either kill or suppress said weeds.
By the term “transparent” in this specification is meant a film that allows visible light and short-wave infrared transmission, therethrough; and by the term “IR retentive” is meant film that blocks the transmission of medium and long-wave infra-red radiation (6-25 micrometers wavelength) therethrough. The transmittance of the film was determined by the ASTM D1003 Test Method.
The present invention in one aspect, therefore, provides for the use of suitable clear (transparent) IR retentive film that has an enhanced absorption of thermal-infrared radiation property and, thus, traps more heat and increases the temperature of the soil relative to that which is otherwise achieved by prior art films, by reducing heat loss from the soil. We have found that enhanced soil temperatures using IR retentive film relative to soil temperatures resulting from clear polyethylene mulches in the method of the present invention have been effective in controlling weeds in the cloudy environment of Florida during the summer months.
We have surprisingly discovered that in the practice of the invention, nutsedge growth is advantageously controlled both by the prevention of germination in the top soil layers and by the “burning” of the newly formed tender growth, due to the accumulated high temperature build-up at the soil surface under the IR retentive film of use in the practice of the invention. We have also found that increased temperatures deeper in the soil under the IR retentive film stimulated germination in these deeper soil layers. Subsequently, this new growth is burned when it grows into the lethal temperatures at the soil surface.
We have found that the high light transmission of the film of use in the invention as defined, preferably, aided by the antifog properties conferred by an antifog additive, warmed the soil and encouraged the nutsedge to sprout and initiate growth. This was followed by “burning” of the tender shoot by the accumulated high temperature and direct light under the IR retention effect of the film. Neither black plastic film nor clear, regular (i.e. none-IR retentive additive) plastic has the heat build-up performance to the extent offered by the IR retentive thermal films to “burn” the nutsedge.
The films may inherently possess the desired degree of IR retentiveness, such as is the case for EVA copolymer films; or the IR retentiveness may be provided by the addition of IR absorbing fillers, such as, for example, silica, aluminum trihydrate, aluminum borate, calcium borate, magnesium borate, zinc borate, anhydrous borax, talc, alunite, and calcium carbonate. The thickness of the film and the amount of IR absorbing filler contained within the film for use in the invention method may be readily determined.
Preferred films of use in the practice of the invention are those having the desired high light transmission and infrared heat retention, and, for example, comprise LDPE, LLDPE or EVA copolymers or mixtures thereof; such as DURA-THERM (Trade mark of AT Plastics Inc.) LDPE/LLDPE mixtures and having IR fillers to retain IR radiation of the range 7-25 mm; and 5-28% w/w VA (vinyl acetate) EVA copolymers.
The invention is thus also of value with films formed of polymers having sufficient intrinsic IR absorbing values at practical gauges without the need for an IR absorbing filler. Examples of such polymers, include, but are not limited to ethylene vinyl acetate (EVA), poly vinyl chloride (PVC); poly vinyl di-chloride, (PVDC); poly vinylidene di-fluoride (PVDF); and thermoplastic urethane (TPU). Thus, unlike those polymeric films which have lower intrinsic IR retention and require an IR additive at the film gauges of practical use, these EVA and the like polymers may be used without an IR filler, although an antifog agent and other additives are still preferably present.
For guidance, films having gauges selected from 1-10 mil and formed of polymers providing at least 30%, preferably more than 50% IR retention of radiation in the range 6 mm-25 mm, than does LDPE film of the same gauge and not containing an IR absorbing filler, are preferred in the practice of the invention in controlling nutsedge.
The practice of the present invention is of particular value in the production of cash crops, particularly, strawberries or tomatoes through weed control, under a hot, cloudy environment.
The nature of the IR film of use in the practice of the invention may be suitably selected by the skilled artisan based on desired properties, such as transparency, IR retention, weight, ease of manufacture, durability resistance to sunlight and the like. The transparency and the IR retentive nature of a suitable film can be readily determined by the skilled artisan for use in the present invention following the surprising discovery that such films have the desired efficacy in controlling by killing or suppressing weeds such as nutsedge.
Preferably, the film is formed of at least one polyolefin. By the term “polyolefin” as used in this specification is meant the polyethylene, polypropylene and polybutadiene family of olefine polymers and copolymers. As examples, high density, low density and linear low density polyethylenes and 1,2-polybutadienes may be mentioned. The term “polyethylene” includes ethylene homopolymers, and copolymers of, such as vinyl acetate, acrylic acid, methyl methacrylate, butene, n-hexene, 4-methyl-1-pentene and octene polymers with ethylene and ble
Chase Carlene A.
Chellemi Daniel O.
Fornari Frank
Sinclair Thomas R.
Batson Victor
Fado John D.
Silverstein M. Howard
Stover G. Byron
The United States of America as represented by the Secretery of
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