Plant husbandry – Process
Reexamination Certificate
2001-03-12
2003-05-20
Jordan, Charles T. (Department: 3643)
Plant husbandry
Process
C047S001500, C047SDIG001
Reexamination Certificate
active
06564508
ABSTRACT:
THIS invention relates to a method of treating a plant or crop and to a treatment installation for the treatment of plants or crops.
Active chlorine in the form of hypochlorous acid, produced by the inorganic and organic hypochlorites and sources of active chlorine such as chlorine gas, sodium hypochlorite bleach (NaOCl), calcium hypochlorite Ca(OCl)
2
and the organic chlorinated isocyanurates (trichloro- and sodium dichloro S-triazines) have been used for over 50 years for post-harvest protection of produce and for the control of fungi and bacteria to prevent rot-spoilage. However, due to phytotoxicity, these compounds have generally not been applied in the spraying of live crops for the control of fungal and bacterial diseases by exploitation of the bactericidal and fungicidal properties of the active ingredient hypochlorous acid. In particular, calcium hypochlorite has generally not been used because of vagaries in dissolution and difficulty in the control of concentration. Calcium hypochlorite of the 65-70% product type contains sodium chloride, which is phytotoxic at the high concentration levels required to produce hypochlorous acid for the killing of fungi and bacteria.
This invention provides a method of using calcium hypochlorite in millimolar quantities for the treatment of plants or crops in the field. In accordance with the invention, the plant cell surface of the crop is exposed to millimolar quantities of non-ionized, covalently bonded, hypochlorous acid, calcium and hydroxide ions in an ideal physiologically balanced form. Because hypochlorous acid is unstable, dissipates and is readily destroyed by light, the method of the invention incorporates the use of a wetting agent to ensure complete contact between plant cell wall and active hypochlorous acid, calcium and hydroxide ions. The result of the treatment is epidermal fortification of the plant cell wall. The invention thus differs from known methods in which microbial organisms are killed by hypochlorous acid.
The invention thus provides a method of treating a plant or crop which includes the step of exposing the plant or crop to an aqueous medium which contains treatment agents which include at least one wetting agent, calcium cations and hypochlorous acid representing therefore a technique of non-exploitation or exclusion of the bactericidal and fungicidal properties of hypochlorous acid, the concentration of the calcium hypochlorite and the calcium being approximately 17.38-34.76 ppm and 7.6-15.2 ppm respectively.
To the best of the Applicant's knowledge, concentrations at this level, which are similar to the physiological concentration of calcium in plants, can only be dispensed in accordance with the method and apparatus of the invention.
Thus broadly, according to the invention, there is provided a method of treating a plant or crop which includes the step of exposing the plant or crop to an aqueous medium which contains treatment agents which include at least one wetting agent and calcium hypochlorite, the concentration of the calcium hypochlorite being between about 17.38 and 34.76 ppm.
The aqueous medium may be a treatment stream and exposing the plant or crop to the aqueous medium may include the steps of
generating an aqueous flow stream from a source of water;
introducing calcium hypochlorite into the aqueous flow stream to produce a treatment stream, the calcium hypochlorite producing hypochlorous acid, hypochlorite ions, calcium ions and hydroxyl ions when it is introduced into the aqueous flow stream, and the calcium hypochlorite being introduced into the flow stream so as to produce a treatment stream having a calcium hypochlorite concentration of between about 17.38 and 34.76 ppm and a calcium concentration of between about 7.6-15.2 ppm;
adding the or each wetting agent optionally to the water from which the flow stream is generated or to the flow stream or to the treatment stream; and
exposing the plant or crop to the treatment stream.
The calcium hypochlorite may be introduced into the aqueous flow stream so as to produce a treatment stream having a calcium hypochlorite concentration of between about 22.88 and 27.44 ppm and a calcium ion concentration of between about 10 and 12 ppm.
The method of the invention will typically be used for the treatment of growing crops. The plant or crop will thus typically be a growing crop. The crop may be selected from potatoes, stone fruit, apples, vines, onions, cucurbits such as pumpkins, melons and squashes, and leafy vegetables such as cabbage, lettuce, brussel sprouts and cauliflower or any crop which is prone to pathogenic or organism attack, including flowers.
The crop may thus be selected from potatoes, stone fruit, apples, vines, onions, cucurbits, leafy vegetables and flowers.
The calcium hypochlorite may be introduced into the aqueous flow stream by using an apparatus for controllably treating a liquid with a liquid treatment substance of the type described in the specification of U.S. Pat. No. 4,842,729.
The advantage of the use of an apparatus of the type described in U.S. Pat. No. 4,842,729 is that the time between contact of the water with the calcium hypochlorite, to form the required hydrolysis products and the time lag to contact the solution of hydrolysis products with the plant is so short that the beneficial ratio of hydrolysis products is retained. If calcium hypochlorite were merely mixed with water, this ionization ratio of hydrochlorous acid, hypochlorite ion and calcium hydroxide would fall into imbalance because of the instability and light sensitivity of hypochlorous acid, sedimentation of calcium hydroxide and because of side reaction of calcium hypochlorite with substances in the water stream. It is well documented that hypochlorous acid and hypochlorite form many defined and non-defined products with substances in water and the formation of these side reaction products is strictly time dependent. It is also well known that, to determine the chlorine demand of water, the tests are done over time periods from contact time to hours after contact time. The distance between the apparatus, e.g. the apparatus, and the sprays and the pressure of the water and the diameter of the conduit used are therefore selected to produce a short delay between formation of the solution and contact with the plant, as is described in further detail below.
The aqueous flow stream will typically be produced from municipal piped water or from irrigation water taken from a river, dam, borehole or the like.
The wetting agent, or surfactant, may be a silicone polyether wetting agent. It may, for example, be a silicone polyether copolymer and alcohol ethoxylate. These wetting agents are particularly suitable because they are not affected by the oxidizing properties of the treatment stream.
The aqueous medium may include about 0.005 to 0.05% and preferably about 0.01% of the wetting agent.
The method may thus include adding the wetting agent to the water from which the flow stream is generated or to the flow stream or to the treatment stream in an amount which is sufficient to produce a concentration of the wetting agent in the treatment stream of about 0.005-0.05% e.g preferably 0.01%. The wetting agent is necessary to enable the treatment stream to readily spread across the entire surface area of the plant which is being treated. The presence of a wetting agent, which allows the treatment stream to rapidly spread across the surface area of the plant so that the hypochlorous acid can rapidly exert its action before it dissipates, is an essential feature of the invention.
Exposing the plant or crop to the treatment stream may include the step of spraying the treatment stream onto the plant or crop with spraying means. The treatment stream may, for example, be sprayed onto the plant or crop via one or more spray nozzles.
The treatment substance may be introduced into the flow stream in an introduction zone of the flow stream.
The invention thus extends to a method of treating a plant or crop, the method including the steps of
generating an aqueous fl
Jordan Charles T.
Klarquist & Sparkman, LLP
PPA Water Industries (Proprietary) Limited
Valenti Andrea M.
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