Blocks of PMU foam with volumes of approximately between 10 cm3 and 100 cm3 become fully cured approximately between 10 and 20 hours when exposed to air at a temperature approximately between 20° C and 30° C having approximately between 70% and 80% humidity. Curing time diminishes as air temperature increases or air humidity decreases or the volume of blocks of PMU foam is reduced. In addition, cured PMU foam has a pH approximately between 2.3 and 2.7 with an acidity of 0.38 to 0.40 meq H+/g dry foam.

The rate of water absorption for PMU foam is dependent on the particle or block size.

Smaller particles or blocks of PMU foam absorb water faster than larger particles or blocks relative to the total water absorption capacity of a particular particle or block. In addition, pure PMU foam holds more water than native materials, while simultaneously maintaining air-filled porosity sufficient for the root-zone aeration of living plants. FIG. 11 shows a larger biomass yield for three varieties of plants grown in pure PMU foam as compared with the same varieties grown in soil without the addition of any PMU foam. The conclusion is that the addition of water to plants grown in pure foam does not diminish the root zone aeration requirements of those plants. Further, FIG. 9 demonstrates that water absorption and water holding capacity of PMU foam is enhanced by the use of a wetting agent. In one embodiment, the brand of wetting agent is AquaGro 2000G.

PMU foam slowly degrades into constituents that provide an extended release pattern for plant-available nitrogen. The forms of nitrogen in PMU foam are free nitrogen, which can be extracted by water, exchangeable nitrogen, which is retained by ionic bonding and can be extracted by 0.02 M KCI, and various chemically complex forms of nitrogen, which are mineralized to exchangeable nitrogen and free nitrogen forms over time by microbial activity.

FIG. 1 illustrates a larger free nitrogen content of PMU foam compared to a smaller exchangeable nitrogen content. With the first drenching or leaching, a significant amount free nitrogen is removed from PMU foam leaving little reserve free nitrogen for continued plant growth. FIG. 3 illustrates this by showing that the extraction of exchangeable nitrogen in the form of ammonium (NH4+) or nitrate (NO,-) leaves a low concentration of free nitrogen available to plants based on overall foam volume. However, under normal conditions, the complex forms of nitrogen contained in PMU foam serve as slow-release source of nitrogen for plants. This nitrogen release is due to further chemical and biological breakdown of the PMU foam structure during environmental exposure. Since nitrate levels in PMU foam are consistently low, the nitrogen form that results from the breakdown of PMU foam is primarily ammonium. FIG. 2 and FIG. 4 illustrate this by showing a variable ammonium concentration over time in a PMU foam mixture. In addition, since ammonium concentration is temperature dependent with higher concentrations present during periods when the mean temperature is elevated, the rate of the chemical and biological breakdown of PMU foam is temperature dependent as well.

Furthermore, PMU foam used a soil ingredient contributes to a well-aerated root zone while maintaining a large volume of plant available water. PMU foam may be used as a component in potting media where retention of plant-available water by the foam serves to reduce the frequency for required watering and delay the onset of drought stress in plants.

FIG. 6 shows that a higher percentage of available water (AW) remains in potting media containing PMU foam as compared to other available potting media. In addition, FIG. 5 shows that incorporating PMU foam into potting media delays the onset of drought stress.

The level of drought stress for plants is determined by measuring the relative extent of leaf wilting and applying a rating scale between 0 and 5 where 0 indicates no stress and 5 indicates that a plant may not recover from wilting. The drought stress rating for potting media with PMU foam remained slight 60 hours after watering. On the other hand, drought stress ratings for comparable potting media without PMU foam were moderate to severe when measured at the same point in time after watering. Furthermore, FIG. 10 shows that potting media containing PMU foam produce a drought stress rating for plants equal to or better than potting media containing commercially available polymer gels designed to aid with water retention.

The present invention discloses a method of using PMU foam as a constituent in potting soil. This is achieved by sub-dividing larger cured PMU foam pieces into smaller pieces, treating the smaller PMU foam pieces with a wetting agent and mixing the treated smaller PMU foam pieces with soil, other soil amendments, potting media, other constituents, or other combinations thereof.

Since PMU foam pieces larger than 10 cm3 are unsuitable as a soil mixture constituent, larger PMU foam pieces may be sub-divided into smaller PMU foam pieces by using conventional shredding methods known to those skilled in the art. In one embodiment, a Troy Built 15 HP shredder may be used to obtain smaller PMU foam pieces, each PMU foam piece having a relatively uniform dimension and each PMU foam piece having a volume of approximately 1 cm3 or less. In a second embodiment, a conventional shredder may be used to obtain smaller PMU foam pieces, which are then passed through a one-quarter inch sieve used to collect PMU foam pieces having a dimension no larger than one-quarter inch.

PMU foam should be shredded before it dries completely and while it retains plasticity.

Shredding foam that remains partially"wet"reduces the amount of dust created during the shredding process. In one embodiment, PMU foam is shredded within twenty-four (24) hours of manufacture. Additionally, the pH of pure PMU foam may be adjusted with the application of a liming agent by applying 10 ml of a 0.039 M KOH solution per g air-dry foam.

Once shredding is complete, shredded PMU foam should be used within two weeks of manufacture. Otherwise, the PMU foam should be stored dry at a temperature of less than 35° C and out of direct sunlight, which reduces the rate of degradation of the PMU foam.

Furthermore, PMU foam should be compacted as little as possible prior to use because any volume loss of the PMU foam due to compaction results in reduced aeration pore space and a reduced ability to hold water.

Once shredded, PMU foam may be used as an ingredient with other constituents to produce potting mixtures having a final PMU foam volume of between 10% and 100% of total potting mixture volume. Mixing may be accomplished by using a commercial tub, rotary, or pug mill type mixer. The constituents of the potting mix are added to the selected apparatus and mechanically mixed until a homogeneous blend is achieved. The process of mixing shredded PMU foam should not be prolonged in order to minimize any reduction of the desired size of the foam particles. In one embodiment, PMU foam incorporated as part of a potting mix is neutralized by adding approximately 40 grams of agricultural lime having 100% calcium carbonate equivalence (CCE) per cubic foot of shredded PMU foam. The application of agricultural lime occurs during blending of the potting mix. Liming agents may include CaCO3, CAOH, or NH40H. Once the pH is adjusted, the resultant potting mixture has a pH of approximately 7.

In one embodiment, shredded PMU foam particles, neutralized with agricultural lime and treated with a wetting agent, having a relatively uniform dimension of between approximately one-quarter inch and one inch are uniformly mixed with varying percentages of shredded pine bark, composted pine bark, sphagnum peat moss, perlite, and vermiculite to achieve a PMU foam volume of between approximately 10% and approximately 60% of total potting soil mixture volume depending upon the desired amount of water retained by the PMU foam constituent. In one embodiment, PMU foam volume is approximately 40% of total potting soil mixture volume. In a second embodiment, PMU foam volume is approximately 50% of total potting soil mixture volume. In subsequent embodiments, any one or more of the recited constituents may be omitted from the resulting potting soil mixture.

In a second embodiment, PMU foam particles, neutralized with agricultural lime and treated with a wetting agent, are uniformly mixed with approximately 10% perlite by volume and approximately 50% peat moss by volume using a standard industrial rotary tub mixer to achieve a PMU foam volume of approximately 40% of total mixture volume. FIG. 6 illustrates the physical properties of this mixture, which provides more plant-available water than comparable mixtures with similar physical properties.

The present invention discloses a method of using PMU foam as a soil amendment.

In one embodiment, this is achieved by mixing a constituent resin with a phosphoric acid catalyst and wetting agent within the pressurized exit stream of a spray nozzle to create sprayed PMU foam. A suitable apparatus for creating sprayed PMU foam is disclosed in U. S.

Pat. No. 4,246,239. The resultant sprayed PMU foam is directed toward existing terrain so that the terrain is covered by the sprayed PMU foam. After sprayed PMU foam is applied, it is allowed to cure in ambient air. Once cured, the sprayed PMU foam is integrated with the existing terrain using conventional garden and farm implements that include, but are not limited to, shovels, picks, rakes, hoes, hand mixers, roto-tillers, tractors, and plows. For those applications requiring 100% PMU foam, no mixing with existing soil is required. In addition, sprayed PMU foam may be applied to existing soil in different patterns including incorporation at a various soil depths or layering on the soil surface. In a second embodiment, cured and cut or shredded foam is applied to existing terrain and integrated using methods similar to those used for sprayed PMU foam. As with sprayed PMU foam, cured and cut or shredded PMU foam may be applied to existing soil in different patterns including incorporation at a various soil depths or layering on the soil surface. FIG. 7 and FIG. 8 illustrate the beneficial effects of incorporating PMU foam into existing soil for turf establishment.

Sprayed, cut, or shredded PMU foam, may be applied to one or more terrain locations with each terrain location having an area between 1 ft2 and 20 mile2, a preferred area between 50 ft2 and 10,000 ft2, and a more preferred area between 500 ft2 and 5,000 ft2. Sprayed PMU foam may be applied over a terrain location to achieve varying depths between 0 inches and 24 inches, a preferred depth between 0.5 inches and 12 inches, and a more preferred depth between 1 inch and 6 inches. Furthermore, there is no requirement that a range of depths be maintained throughout any one particular terrain location since the requirements for PMU foam may vary within that terrain location. If sprayed PMU foam is applied to a terrain location, it is allowed to cure by air-drying for a time period between 30 minutes and 2 days.

In one embodiment, sprayed PMU foam is allowed to cure for 2 hours. In one embodiment, after sprayed PMU foam is cured, it is neutralized with a KOH solution. In a second embodiment, sprayed PMU foam is not neutralized after it is cured. Next, sprayed, cut, or shredded PMU foam is incorporated into underlying terrain by rototilling or similar method.

Conventional planting methods, such as broadcast seeding or hydraulic mulching, may be used to establish growing plants.

FIG 7 and FIG 8 illustrate the improved establishment of fine turfgrass at two different locations. At one site in Blacksburg, Virginia, the existing terrain was natural soil ; and, at a second site in Petersburg, Virginia, the existing terrain was disturbed and filled roadway soil. The early establishment and growth phases between approximately 1 month and approximately 4 months after planting showed more terrain coverage by turfgrass than achieved by planting solely in existing terrain. In addition, the fine turfgrass planted in terrain with integrated sprayed PMU foam had higher germination rates, faster plant establishment, and more uniform stands of turf as compared to standard establishment techniques. For each of the measured parameters, including percent coverage, clipping weight, and plant height, the incorporation of PMU foam into existing soil improved plant establishment and growth.

The present invention discloses a method of using PMU foam as a soil substitute.

This is achieved by mixing a constituent resin with a phosphoric acid catalyst and wetting agent within the pressurized exit stream of a spray nozzle to create sprayed PMU foam. The resultant sprayed PMU foam is directed toward existing terrain so that the terrain is covered by the sprayed PMU foam. Once applied to a terrain location, PMU foam is allowed to cure by air-drying for a time period between 30 minutes and 2 days. In one embodiment, PMU foam is allowed to cure for 2 hours. In one embodiment, after the PMU foam is cured, it is neutralized with a KOH solution. In a second embodiment, the PMU foam is not neutralized after it is cured. Once cured, grass seeds or seedlings may be planted in the PMU foam layer by conventional means such as broadcast seeding, hydraulic mulching, or applying straw mulch and fertilizer.

Sprayed PMU foam may be applied to one or more terrain locations with each terrain location having an area between 1 ft2 and 20 mile2, a preferred area between 50 0 f and 10,000 ft2, and a more preferred area between 500 f and 5,000 ft2. Sprayed PMU foam may be applied over a terrain location to achieve varying depths between 0 inches and 24 inches, a preferred depth between 0.5 inches and 12 inches, and a more preferred depth between 4 inches and 6 inches. Furthermore, there is no requirement that a range of depths be maintained throughout any one particular terrain location since the requirements for sprayed PMU foam may vary within that terrain location.

While the present invention has been particularly described, it will be understood by those skilled in the relevant art that various changes in form and detail may be made without departing from the spirit and scope of this invention.

DESCRIPTION OF THE DRAWINGS The following figures are referred to in the Description of the Invention: FIG. 1 is a table of the chemical properties of PMU foam.

FIG. 2 is a table showing the amount of nitrogen in PMU foam extractable in KCI.

FIG. 3 is a graph of nitrate release by potting media with and without PMU foam during laboratory incubation at 20° C.

FIG. 4 is a graph of ammonium release patterns of PMU foam, a PMU foam potting mixture, and commercial potting media during laboratory incubation at 20° C with weekly leaching.

FIG. 5 is a table showing the effect of potting media containing PMU foam in delaying the onset of drought stress in tomato plants.

FIG. 6 is a table of physical property parameters of a PMU foam potting mixture and comparable commercial media.

FIG. 7 is a table showing turf establishment with different scenarios of PMU foam applications.

FIG. 8 is a table showing the effect of PMU foam and tillage on the establishment of turfgrass.

FIG. 9 is a table showing the effect of a wetting agent on water absorption by PMU foam.

FIG. 10 is a table showing various potting media and polymer gel effects on delaying drought symptoms in tomato plants.

FIG. 11 is a series of three graphs showing the effect of soil/foam ratio and liming of foam material on plant biomass yield.