Crop cultivation methods
Open-field cultivation is a method for growing crops and flowers in ordinary fields, not in greenhouses or under rain shelters.
Rain shelter cultivation is a method in which the crops are covered with a roof made of vinyl, etc. to protect them from rain and prevent excess moisture and soil from flowing out.
Facility cultivation is a method for cultivating crops in facilities such as plastic greenhouses and glass houses and can be further divided into soil cultivation and hydroponics, which uses no soil in the cultivation. We will further explain the facility cultivation method.
Advantages and disadvantages of the facility cultivation method
Vinyl greenhouse cultivation will be focused on here, which is a representative example of facility cultivation. Although the type of crop and the season of cultivation may be influencing factors, if the same vegetables are cultivated in the same area in an open field and a plastic greenhouse, the yields of the plastic greenhouse will be much more. This means that the latter has higher productivity. It is because plastic greenhouses can provide suitable growing conditions for crops, such as temperature and humidity.
Moreover, vinyl greenhouses can protect crops from wind and flood damage, as well as birds and beasts.
First of all, greenhouse construction and equipment are costly. Furthermore, generally speaking, it takes more effort than open-field cultivation to increase the crops yield, requiring considerable labor for each unit area.
However, next-generation environmental control devices that better control the cultivation environment are also emerging. The introduction of such equipment requires a corresponding initial investment, which can be partially compensated by administrative subsidies. These new environmental control devices also help to save on labor.
About vinyl houses
In some cases, the entire greenhouse is covered with films, while sometimes only the top of the house is covered to shield the crops from rain. The crops-growing method where only the top of the house is covered is a form of the rain shelter cultivation method mentioned earlier.
Although PVC film is excellent for heat retention, it is weak in weather resistance, that is, poor resistance to changes in climate. Deterioration of the films are visible.
Recently, agricultural polyolefin films and fluorine resin films with excellent weather resistance have been developed, and their shares of the market are expanding annually. A number of films have also been developed with different functions suitable with the cultivation method, which can suppress the rise of humidity and the occurrence of fog in the vinyl house and prohibit the transmission of ultraviolet light.
Are vinyl houses considered buildings?
Any roofed structure fixed to the ground having columns or walls (including any other similar structures) …((Article 2 item (1) of the Building Standard Law))
In other words, if the building exceeds a certain scale, it is necessary to submit an application to the relevant government office to obtain the approval of officials.
However, when building a vinyl house, you are rarely required to apply for approval.
When the building is used to carry out agricultural activities such as growing crops, making crop seedlings, drying crops, and other production activities, there is no need to submit an application.
However, this is not the case when a new vinyl house is built on a residential site. Since residential lands are not supposed to be used for farming, without the approval of the construction department of the municipalities or prefectural engineering works offices, there may be cases in which vinyl houses are considered illegal and will not be allowed to be constructed.
PVC, polyethylene, polypropylene
Some plastics are used as materials for plastic greenhouses and various agricultural materials, each of which will be explained below to help you better understand their applications as agricultural materials.
①PVC (polyvinyl chloride)
It has long-time solvent resistance properties, such as water resistance, acid resistance, and alkali resistance. Moreover, it is resistant to flames and excellent in electrical insulation and is thus often used for the insulation coating of electric wires, water pipes, etc. which must be used for a long time.
However, it is weak to ultraviolet light. Continuous exposure to ultraviolet rays may deteriorate and damage this plastic.
Polyethylene is a kind of plastic with many benefits.
Its benefits include cheap raw materials and excellent processability; outstanding mechanical strength, especially under low temperature; high chemical resistance; and weather resistance. It is also highly resistant to water because it absorbs practically no water.
On the other hand, it also has several disadvantages.
Due to poor adhesive property, the material must be carefully handled in painting and printing. With low heat resistance, it is vulnerable to fire and heat.
Polyethylene is the most widely used plastic and has the largest production.
The thinner the polyethylene is, the more versatile it is. It is used in a variety of places, such as stationery and packaging materials, textiles, plastic parts, renewable containers, car parts, and bills.
Due to its low specific gravity, it can float on water. It is also hard, non-absorbent, and resistant to chemicals.
However, it is generally not used for making highly fashionable textiles because it is difficult to dye and vulnerable to light.
Polyolefin is a generic term for resins with double bond of hydrocarbon and includes both polyethylene and polypropylene.
Agricultural materials for KEIWA Incorporated
Aluminum reflective sheets for agricultural use. An aluminum-metallized film and a mulch film are pasted together to increase the durability of the aluminum layer. It can keep the temperature and humidity of the soil constant and promote the germination of crops. It is also excellent at reflecting sun rays and contributes to pest control.
It is a sheet where aluminum-metallized films and mulch films are laminated. By pasting the film in a vinyl house, it can exert a heat retention effect and contribute to energy saving. It can also block out direct sunlight in poultry and pig houses.
It is also made by laminating aluminum-metallized films with mulch films. By covering the vinyl house with the material, it can reflect sunlight and lower the internal temperature to provide a cooling effect. It is also used for sericulture facilities and poultry houses.
By reflecting sunlight, it promotes the growth of fruits, etc. and exerts an effect in terms of coloring and head sprouting.
As a weatherproof and transparent sheet, it is used as polyolefin gutter sheets for multi-span greenhouses. It is 1 mm thick and transparent; and it does not interfere with the growth of plants since it cannot shade raindrops on the ground.
⑥Water Stop Sheet
It is a base sheet made of a colored polyolefin sheet with excellent weather resistance and strength and is suitable for long-term use. It has excellent heat-retention property and is helpful for preventing insect incursion and contaminated water.