Plant husbandry – Mulching
Reexamination Certificate
1999-11-05
2001-09-25
Poon, Peter M. (Department: 3643)
Plant husbandry
Mulching
C047S00101T
Reexamination Certificate
active
06293045
ABSTRACT:
BACKGROUND
Various materials have been used as agricultural and horticultural mulch to enhance plant growth and improve soil, e.g. by conserving water, elevating soil temperature, controlling weeds, and adding organic mater to soils. Such materials have included straw, composted matter, manure, shredded bark and wood, fabric and plastic film. A decision to use mulch is usually based on the ability to achieve improvements over non-mulching agriculture practices which may require intense cultivation to control weeds and conserve water. Among the common mulch materials, plastic film is preferred for use with many cash crops, e.g. vegetables and ornamentals, due to its low cost and effectiveness in weed control and elevating soil temperature. Among the disadvantages of plastic film are poor distribution of irrigated water and the need to strip the film from fields after the growing season. Moreover, plastic film does not improve soil as organic mulch materials can do when incorporated into the soil. A soil with preferred tilth may comprise equal volumes of air, aggregate, organic matter and water. An advantage of a biodegradable mulch mat is that it can contribute to a preferred level of tilth when incorporated into the soil.
Likewise, in horticulture a variety of materials have been used to improve the aesthetic appearance of landscaping, suppress weeds and conserve moisture in soil around ornamental plants. Such materials include peat moss, chopped bark, shredded wood, compost, gravel and the like. Each of the materials has one or more deficiencies, e.g. with regard to weed suppression, moisture retention, biodegradation and appearance.
Jamison discloses in U.S. Pat. No. 3,812,615 a foamed material comprising fiber and an epoxy-crosslinked, acrylic polymeric binder intended as an agricultural mulch. The epoxy crosslinker renders the binder relatively non-biodegradable. And, as disclosed in comparative Example 13, such foamed material is not effective in suppressing weeds.
SUMMARY OF THE INVENTION
This invention provides a biodegradable mulch mat which is readily applied to soil or garden areas, e.g. as an aqueous foam, and provides desirable conservation of water, weed control and soil temperature maintenance. The mat comprises an open cell structure which is air and water permeable which provides superior distribution of natural or irrigated water to the soil and desired oxygen access to the soil. In preferred aspects of this invention the mulch mat exhibits the unique property of high water absorption and retention as well as high water permeability after saturation. Although the mat has an open cell structure, it exhibits superior weed suppression. The mat comprises biodegradable fiber and granules held together in an open cell structure by a biodegradable binder which is more readily decomposed by microorganisms than the fiber and granules. The choice of binder allows design of a mat with a desired cycle life ranging from a few months for agricultural applications to years for horticultural applications. The use of biodegradable materials allows a used mulch mat to be turned into the soil to build tilth by increasing soil openness and adding organic matter.
Although the mulch mat is useful in suppressing the growth of weeds from beneath the mat, the mat has the surprising advantage of permitting seeds to take root through the mat from above, e.g. from a seed-germinating medium on the surface of the mat. In other aspects of the invention the mulch mat can comprise useful additives for agriculture and horticulture applications; such additives can comprise surfactants, soil builders, plant nutrients, soil conditioners, fungicides, bactericides, nematocides and the like.
The mulch mat is a tough, durable unitary structure which can be applied to a variety of two-dimensional or three-dimensional surfaces including tilled soil, slopes and mounds, natural gardens, rocks, metal frames, lattice, timbers, pots and the like. Especially for horticulture applications the mulch mat can be applied in a variety of colors to aesthetically complement or coordinate with the local environment or plantings. This is an advantage when plants growing in a mulch mat are arranged in an artistic or information-conveying, patterned display, especially for multi-color presentations.
This invention also provides horticultural gardens comprising horticultural plantings in the biodegradable mulch mat, including vegetable and flower gardens, landscaping, tree and shrubbery nurseries, etc. Such a garden can be prepared by applying foam around the stalks of plants or seedlings, by inserting plants through holes in a preformed mulch mat or by applying seed and growing media to the surface of a mulch mat. The mulch mat can be colored, e.g. with mineral or plant colorants, to enhance the aesthetic effect of the garden.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
As used herein the term “percent solids” is based on all non-liquid, air-free, components of a formulation. As exemplified herein, the components of slurries useful for making foams which are precursors to mulch mats are typically solid or can be dried to a solid or non-aqueous liquid of high vapor pressure; thus, the “percent solids” represent the non-water components.
The biodegradable mulch mat of this invention can be prepared from a foamed dispersion of biodegradable fibers, granules, binder and other additives. When the wet foam dries, the mulch mat is formed with fibers and granular material maintained in an open celled composite structure by binder. Such open celled mats are permeable to water and air and impermeable to light. Mulch mats prepared without fiber or without granular material tend to have undesirable properties, e.g. high frangibility or impermeability. For instance, mulch mats prepared without granular material tend to have the properties of paper mache without an open celled structure. Very thin mache mats are so open to light as to be ineffective in suppressing weeds. Thicker mache mats tend to be excessively frangible and prone to cracking resulting in high weed growth through cracks. Very thick mache mats while durable tend to be highly impermeable which does not enhance plant growth. As illustrated in comparative Example 13, below, a fiber mat prepared from a foam with an epoxy-crosslinked binder is durable but so open-celled as to be relatively ineffective in suppressing weeds.
The mulch mats of this invention comprise biodegradable fibers which can be natural or synthetic fibers, e.g. cellulosic fibers, protein fibers or synthetic polymer fibers. Natural fibers can comprise pulped or shredded cellulose fibers such as wood pulp, shredded wood, shredded paper (tissue, newsprint and the like), straw, cotton fiber, composted vegetation, fibrous sphagnum moss, peat moss, shredded stalks including shredded corn stalks and shredded pine straw (including needles, twigs, cones and small branches). Shredded vegetation is preferably dry before shredding. Protein fibers can comprise as hair or gelatin. Biodegradable synthetic fibers can comprise reconstituted cellulose fibers such as rayon fibers, vinyl polymer fibers such as fibrous polyvinyl alcohol and polyamide fibers. In preferred embodiments of this invention the mulch mats will comprise fiber having a high aspect ratio of length to diameter, e.g. of at least 3, more preferably of at least 10 and even more preferably of at least 30. In general fine fibers, e.g. from shredded newsprint, are preferred due to the low cost of shredded newsprint and because of the superior performance of such over larger fibers such as straw. Because the black inks in newsprint are typically biodegradable, shredded newsprint with black ink is preferred over newsprint with colored ink. Even more preferred is unprinted, shredded newsprint, e.g. overstock, leader or end of roll newsprint.
The biodegradable mulch mat of this invention also comprises granular material which can be biodegradable or not. Biodegradable granular material can comprise organic particulate prepared by milling hard vegetation suc
Gellner Jeffrey L.
Kelley Thomas E.
Poon Peter M.
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