JP7609745B2 - Spraying materials and spraying layer formation method - Google Patents

Description

The present invention relates to a spraying material and a method for forming a sprayed layer.

Traditionally, vegetation substrate spraying work has been known as a method for greening soil and bedrock surfaces. In vegetation substrate spraying work, seeds are impregnated with vegetation substrate and sprayed onto the target surface to cause the seeds to germinate. However, if the vegetation substrate is continuously exposed to sunlight and wind after spraying work, water will evaporate from the surface, causing it to dry out, which can result in the seeds failing to germinate. For this reason, it is desirable to refrain from greening work during periods of low rainfall as this risk is high, but it is sometimes unavoidable to carry out work in conjunction with other processes. As a result, there have been cases where rework was required due to failure to achieve greening.

The causes of drying include the low water retention of bark compost, which is widely used as a vegetation substrate, and the fact that it becomes water repellent when it dries, making it difficult to absorb water. Therefore, spray materials containing surfactants have been proposed to suppress water repellency (Patent Document 1).

Patent No. 4048800

However, even if water penetrates soil with reduced water repellency, if the soil has insufficient water retention, the water evaporates quickly and plants find it difficult to survive. The present invention aims to provide a spraying material that can produce a sprayed layer with high water retention when applied to soil or rock surfaces for the purpose of greening. It also aims to provide a method for forming a sprayed layer that uses this spraying material.

The present invention provides a spray material that includes a vegetative substrate and a water-retentive material, the water-retentive material containing at least one of a silicate clay mineral and biochar, and the water-retentive material containing black soil in an amount of 5% or less of the total volume of the vegetative substrate and the water-retentive material (100%).

Because this spray material contains water-retentive materials, the sprayed layer obtained by spraying this spray material has high water-retentive properties, is less likely to dry out, and is favorable for plant growth. Furthermore, by using this spray material, greening work can be carried out even during dry seasons.

The spray material may further contain a penetrating agent. If the spray material contains a penetrating agent, the spray layer obtained by spraying the spray material will be more likely to absorb water. In other words, water repellency will be suppressed. The water-retentive material may also contain biochar, and the biochar content may be 1% to 60% of the total volume of the vegetation substrate and the water-retentive material, which is 100%.

In this spray material, the water-retentive material contains silicate clay minerals and biochar, and the content of biochar is preferably greater by volume than the content of silicate clay minerals. In addition, this spray material may further contain fertilizer and may contain an adhesive. The adhesive acts to bond the particles of the spray material, so that when this spray material is sprayed onto a slope, it is possible to prevent the sprayed layer from sliding off.

The present invention also provides a method for forming a sprayed layer by spraying the above-mentioned spray material onto a target surface to form a sprayed layer. Here, the target surface may be a slope.

According to the present invention, it is possible to provide a spraying material that can obtain a sprayed layer with high water retention when applied to soil or bedrock surfaces for the purpose of greening. It is also possible to provide a method for forming a sprayed layer that utilizes this spraying material.

A preferred embodiment of the present invention will be described in detail below. The spray material of this embodiment is sprayed onto horizontal surfaces or slopes to form a sprayed layer that serves as a base for vegetation, with the aim of greening the surfaces of soil and bedrock, or concrete, etc. The spray material of this embodiment contains seeds, so that the seeds germinate from the sprayed layer and the plants grow, greening the target surface.

The spray material of this embodiment includes a vegetation substrate, a water-retentive material, an adhesive, and seeds. The spray material may further include fertilizer. The spray material may also include a penetrating agent to increase water permeability.

The vegetation substrate preferably has the water retention required for plant growth, and is preferably an organic material. Examples of the vegetation substrate include bark compost and a mixture of bark compost and at least one of leaf mold, peat moss, coconut fiber, etc. The dry specific gravity of the vegetation substrate is preferably 0.05 to 0.45 g/ ^cm3 , and more preferably 0.15 to 0.3 g/ ^cm3 .

The water-retentive material is a material that has higher water-retentive properties than the vegetation substrate. The water-retentive material may be an inorganic or organic material, and examples thereof include silicate clay minerals, biochar, palm fiber, peat moss, wood fiber, inorganic porous materials, and ceramic materials. Among these, the water-retentive material includes either silicate clay minerals or biochar. It is also preferable to include both silicate clay minerals and biochar. Since silicate clay minerals are rich in silicic acid, they are expected to improve the strength and disease resistance of plants that have a high silicic acid requirement, such as grasses.

Examples of silicate clay minerals include zeolite, kaolinite, and smectite. Of these, bentonite, which is mainly composed of montmorillonite, a type of smectite, is preferred. Bentonite strongly adsorbs water, thereby suppressing water evaporation and slowing the drying of the sprayed material. Bentonite that swells little due to water absorption is preferred, and from this perspective, calcium-type bentonite is preferred. In particular, when applying the sprayed material to slopes, it is preferred that the degree of swelling due to water absorption is small.

The content of silicate clay minerals is preferably 0.01% to 50% of the total volume of the vegetation substrate and water-retentive material (100%), more preferably 0.1% to 25%, and even more preferably 0.5% to 15%.

Biochar (plant charcoal) is a carbonized organic material. Biochar is generally porous, so by retaining water in its fine pores, evaporation can be suppressed and water can be provided to plants. The pores also provide breathing space for plant roots and can be used by microorganisms, so an increase in useful microorganisms can be expected. Examples of biochar include rice husk charcoal, coconut shell charcoal, wood charcoal, and bamboo charcoal. Since biochar is not easily decomposed in soil, using it as a constituent material of the spray material of this embodiment is expected to have the effect of storing carbon dioxide absorbed by plants from the atmosphere in the soil.

The content of biochar in the spray material is preferably 1% to 60% of the total volume of the vegetation substrate and water-retentive material (100%), more preferably 5% to 50%, and even more preferably 10% to 40%. In particular, when using rice husk charcoal as biochar, since rice husk charcoal is an alkaline material with a pH of 8 to 9, it is preferable that the content does not exceed these upper limits. Furthermore, in soil with a high pH, there is a risk that invasive species such as Solidago altissima (designated as an invasive species requiring caution under the Invasive Alien Species Act) will invade more easily than native species.

The relative ratio of the content of silicate clay mineral to biochar may be, from the viewpoint of suppressing water repellency (enhancing water permeability), the content of biochar may be 1 to 40 times, 1.5 to 20 times, or 2 to 10 times the volume of the silicate clay mineral.

The water-retentive material may contain black soil, but in the spray material of this embodiment, the black soil content is 5% or less of the total volume of the vegetation substrate and the water-retentive material, which is 100%. If this content exceeds 5%, the water-retentiveness tends to decrease.

Any type of fertilizer may be used as long as it is one that is normally used as a fertilizer for plants. The amount of fertilizer to be mixed is preferably 50 g/ ^m2 to 150 g/ ^m2 based on the area of the sprayed layer when the spray material is sprayed to form a sprayed layer. When the total weight of the vegetation substrate and the water-retentive material is taken as 100%, it is preferable to mix in an amount of 1% to 5% by weight.

The adhesive bonds the particles in the spray material together to prevent the spray layer from sliding off when the spray material is applied to a slope to form a spray layer. The adhesive is preferably an organic polymer, and in particular polyvinyl acetate, vinyl acetate-ethylene copolymer, and polyvinyl alcohol are preferred. The adhesive content may be 0.05% to 2%, or 0.1% to 1%, when the total volume of the vegetation substrate and water-retentive material is taken as 100%.

The penetrating agent is intended to increase the water permeability of the sprayed layer (suppress water repellency). If the sprayed layer has high water permeability, rainwater will easily penetrate during rainfall, and water retention is likely to be exerted. The penetrating agent is preferably a surfactant, and any of anionic surfactants, cationic surfactants, amphoteric surfactants, and nonionic surfactants can be used. From the viewpoint of mixability, the penetrating agent is preferably a liquid, and the amount to be mixed may be 0.01 mL/L to 2.5 mL/L, or 0.03 mL/L to 0.25 mL/L based on the total volume of the vegetation substrate and the water-retentive material.

The degree of water repellency can be determined by a water repellency test. For example, according to the WDPT method (Bisdom et al., 1993), the time it takes for a 0.5 mL water droplet to penetrate can be recorded. In the WDPT method, the target material is spread on a petri dish, and the dryness of the target material is set to the value that indicates the highest water repellency (e.g., volumetric water content of 20%). Then, the water droplet penetration time (unit: seconds) is used to evaluate the water repellency into one of five levels (WR0 to WR4):
Less than 5 seconds: WR0 (no water repellency)
・5 seconds to less than 60 seconds: WR1 (slight water repellency)
・60 seconds to less than 600 seconds: WR2 (strong water repellency)
600 seconds to 3600 seconds: WR3 (significant water repellency)
Over 3600 seconds: WR4 (extreme water repellency)

Seeds include seeds of grasses, legumes, and woody plants such as birch and rose. The amount of seeds to be used is determined taking into consideration the greening target, region, construction period, etc.

The procedure for spraying spray materials involves first mixing various materials. For example, vegetation base material, water-retentive material, adhesive, penetrant, fertilizer, and seeds are added to the tank of a spray machine such as mortar and mixed. This prepares the spray material. The materials to be mixed can be added in any order, and the addition of any material can be delayed. For example, seeds can be added after the materials other than the seeds have been thoroughly mixed.

The target surface to which the material is sprayed may be a horizontal plane or a slope. If it is a slope, the gradient may be up to 1:0.6. An anti-slip material such as a lath net is provided on the target surface, and the spray material is pumped and discharged from a nozzle onto the anti-slip material. The spray thickness is determined by the construction conditions, such as the rock type of the substrate, the soil gradient, and the type of plant used, and ranges from 3 cm to 10 cm. In this way, a sprayed layer can be formed on the target surface.

Spraying vegetative substrates is a known method for greening soil and bedrock surfaces, but if the vegetative substrate is exposed to sunlight and wind for a long period of time after spraying, water evaporates from the surface, causing it to dry out and resulting in seeds failing to germinate. As a result, it is best to refrain from carrying out greening work during periods of low rainfall, as this risk is greater, but it has sometimes been necessary to carry it out due to other processes. As a result, there have been cases where rework was required due to failure to achieve greening.

If the water retention of the sprayed layer is insufficient, water evaporates quickly, making it difficult for plants to grow. In particular, on slopes, if the water retention is insufficient, water is likely to run off even when it rains. In this regard, since the sprayed material of this embodiment contains a water retention material, the sprayed layer obtained by spraying this sprayed material has high water retention. Therefore, with this sprayed layer, the water retention under dry conditions is higher than with conventional vegetation substrates, and the survival period of plants can be extended. In addition, since the sprayed layer is difficult to dry out, greening work can be carried out even in dry seasons by using the sprayed material of this embodiment. Therefore, the construction period can be freely set regardless of the season.

The spray material of this embodiment contains a penetrating agent, which makes the spray layer more likely to absorb water, and it can efficiently absorb even small amounts of rain. In addition, the spray material of this embodiment contains an adhesive, which bonds the particles of the spray layer together, making it applicable to slopes where there is a risk of the spray layer sliding off.

The above describes a preferred embodiment of the present invention. The present invention is not limited to the above embodiment. For example, in the above embodiment, the spray material contains seeds, but it may not contain seeds, and after forming the spray layer, seeds may be sown, or a greening sheet with seeds or the like attached thereto may be laid. Also, instead of sowing seeds, seedlings may be planted in the spray layer. Furthermore, the surface to be sprayed may be concrete or mortar, in addition to soil or bedrock.

Below, experimental examples are presented to evaluate the water retention and water repellency of the spray material of the present invention. Note that the present invention is not limited to the following experimental examples.

<Water retention study>
A 1.125-liter container (150 mm x 150 mm x 50 mm) was prepared. The vegetation substrate and water-retentive material shown below were mixed in the volume ratios shown in Table 1 (Experimental Examples 1 to 24), and an adhesive was added in an amount that would make up 0.2% of the total volume of the mixture, assuming that the total volume was 100%, to prepare modified vegetation substrates. In each experiment, the container was filled with 1.5 times the volume of the modified vegetation substrate. 150 seeds were sown per experiment.

(Materials used)
[1] Vegetation substrate (mainly composed of bark compost: product name "Fujimi Soil", manufactured by Fujimi Kogyo Co., Ltd., dry bulk density 0.18 g/cm ³ )
[2] Water-retentive materials: Bentonite (calcium bentonite: product name "Bentonite Granules", manufactured by AgriCreate Co., Ltd.)
・Black soil (product name "Black soil", manufactured by Togawa Heiwa Farm Co., Ltd.)
・Rice husk charcoal (product name "Green Power Biocharcoal", manufactured by Kansai Sangyo Co., Ltd.)
・Coconut shell charcoal (product name "HiPro C", manufactured by King Coal)
・Coconut fiber (product name "Kokoyuki", manufactured by DIA)
・Peat moss (product name "Peat Moss", manufactured by Togawa Heiwa Farm Co., Ltd.)
・Wood fiber (product name "DW Fiber", manufactured by Daiken Corporation)
[3] Adhesive (vinyl acetate-ethylene copolymer: product name "Lunasol Powder S", manufactured by Japan Coating Resin Co., Ltd.)
[4] Seeds (annual ryegrass seeds)

Each container containing the seeds was left to grow in an artificial climate chamber with a temperature of 25°C and humidity of 55%, with a light/dark cycle and water absorption cycle of 12 hours. Watering was stopped 14 days after sowing, or when germination of 45% or more (half ± 5%) was confirmed. The number of days it took for more than half of the test grass to wilt was then recorded as the number of days the grass survived under dry conditions. The results are shown in Table 1.

According to the results shown in Table 1, when bentonite or biochar (rice husk charcoal, coconut shell charcoal) was mixed as a water-retentive material (Experimental Examples 2-5, 13-18), the plant survival days were longer than when only the vegetation substrate was used (Experimental Example 1). When coco peat, peat moss, or wood fiber was used as a water-retentive material (Experimental Examples 19-24), the effect of extending the plant survival days was not as high as when bentonite or biochar was used. When black soil was mixed at 5% as a water-retentive material (Experimental Example 6), the plant survival days were longer than when only the vegetation substrate was used (Experimental Example 1), but when more than 5% was mixed (Experimental Examples 7-12), the plant survival days decreased. This is thought to be due to a decrease in the amount of water retention due to a decrease in the voids in the modified vegetation substrate.

<Study on water retention and water repellency>
In addition to the water retention improvement effect, the presence or absence of a water repellency suppression effect was also examined. The same vegetation substrate and water-retentive material (bentonite, rice husk charcoal) used in the above water retention study were mixed in the volume ratios shown in Table 2, and an adhesive was mixed in an amount that would make the volume 0.2% when the volume of these was taken as 100%, and a penetrant (non-ionic surfactant: trade name "Good Touch", manufactured by Maruwa Biochemical Co., Ltd.) was mixed in an amount that would make the total volume of the vegetation substrate and water-retentive material 0.063 mL/L to prepare a modified vegetation substrate. The modified vegetation substrate was filled in the same container as used in the above water retention study, and seeds were sown.

Each container containing the seeds was left to grow in an artificial climate chamber with a temperature of 25°C and humidity of 55%, with a 12-hour light/dark cycle. Watering was stopped 14 days after sowing, or when germination of 45% or more (half ±5%) was confirmed. The number of days it took for more than half of the test grass to wilt was then recorded as the number of days the grass survived under dry conditions. The results are shown in Table 2.

In addition, each modified vegetation substrate was separately filled into a petri dish (7 cm in diameter) and the water droplet penetration time was measured. The water repellency test was performed according to the WDPT method by recording the time required for a 0.5 mL water droplet to penetrate. The drying conditions were a volumetric water content of 20%, at which point the unmodified vegetation substrate showed the highest water repellency in preliminary tests. The results are shown in Table 2. In Table 2, the "water droplet penetration time" is expressed as an integer value rounded off to the first decimal place.

According to the results shown in Table 2, when bentonite and rice husk charcoal were mixed as water-retentive materials (Experimental Examples 26-34), the number of days plants survived was longer than when only the vegetation substrate was used (Experimental Example 25). In addition, it was found that increasing the mixing ratio of rice husk charcoal (Experimental Examples 26-28, 29-31, 32-34) increased water permeability (increased degree of suppression of water repellency). It was found that when the amount of bentonite was greater than the amount of rice husk charcoal (Experimental Examples 29 and 32), water repellency increased. In Experimental Example 32, the specified germination rate was not reached even after a certain period of time had passed (germination rate 40.8%). This is thought to be due to the increase in water repellency due to the increase in the amount of bentonite, and the formation of water-blocking areas due to the local concentration of bentonite, which inhibited the seeds from absorbing water.

The present invention can be used, for example, as a slope revegetation work.

Claims (8)

A vegetative substrate and a water-retentive material are included,
The water-retentive material includes silicate clay minerals and biochar ;
The content of the biochar is equal to or greater than the content of the silicate clay mineral by volume ratio;
The water-retentive material is a spray material having a black soil content of 5% or less out of a total volume of 100% of the vegetation base material and the water-retentive material. The spray material according to claim 1, further comprising a penetrating agent. The spray material according to claim 1 or 2, wherein the content of the biochar is an amount that occupies 1% to 60% of the total volume of the vegetation base material and the water-retaining material, which is 100%. The spray material according to any one of claims 1 to 3, wherein the content of the biochar is greater by volume than the content of the silicate clay mineral. The spray material according to any one of claims 1 to 4, further comprising a fertilizer. The spray material according to any one of claims 1 to 5, further comprising an adhesive. A method for forming a sprayed layer, comprising spraying the spray material according to any one of claims 1 to 6 onto a target surface to form a sprayed layer. The method for forming a sprayed layer according to claim 7, wherein the target surface is a slope.