JP2000184828A - Heat sterilization of soil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat sterilization method for soil capable of effectively killing pathogenic microorganisms in soil. SOLUTION: Plural pipes 3 are buried in the soil in a greenhouse 2 at a depth of 40-80 cm from the ground surface, the soil is warmed by passing hot water or hot liquid into the pipes 3. When this ground warming apparatus is used, the temperature in the soil is elevated due to both solar heat and underground warming to perform heat sterilization of the soil 4. Or, hot air is sent into soil by supplying hot air in stead of hot water or hot liquid into perforated pipes buried in the ground, and thus the temperature of the soil is elevated. Thus, the temperature of the soil at 60 cm depth from the ground surface is effectively elevated to 50-60 deg.C, and the soil within 60 cm in depth can be completely sterilized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for growing crops by underground heating of house cultivation in winter and a method of disinfecting soil by combined use of underground heating and solar heat in summer.

[0002]

BACKGROUND OF THE INVENTION Soil diseases of agricultural products are mainly caused by pathogens inhabiting the soil. Conventionally, such soil diseases have been controlled with agents such as chloropicrin and methyl bromide. However, in recent years, there has been increasing interest in agricultural products, and to avoid the harm caused by spraying toxic drugs such as chloropicrin, and because methyl bromide is an ozone depleting substance and will be banned in the future, drug-independent solar disinfection has recently been carried out. Is being done.

[0003] Since solar heat disinfection is safe and can be expected to be effective, it is applied to tomatoes, cucumbers, strawberries, watermelons, spinach and the like. Extremely effective heat disinfection includes strawberry yellow blight, eggplant wilt, tomato root rot, green pepper rot, spinach seedling blight, sclerotium disease of various crops, and white silkworm disease. The most effective are tomato brown root rot, sunspot rot, tomato wilt,
Fusarium disease such as cucumber vine disease.

[0004] The solar heat disinfection is a measure for killing pathogenic bacteria, nematodes and weed seeds in the soil by raising the temperature of the soil using solar heat in summer. Usually, solar thermal disinfection includes so-called greenhouses (including greenhouses such as other plastics and glass; those that have a space that receives sunlight and are substantially isolated from the outside air; hereinafter referred to as "houses") or vinyl tunnels (other plastics and glass). Tunnel made of glass, etc., which is lower than the house. It is called a tunnel, and a vinyl mulch (which directly covers the soil surface. It is called a mulch, hereafter). Will be

[0005] Soil disinfection requires a soil temperature of 40 ° C or higher, depending on the type of pathogenic bacteria, and requires an accumulated time of 40 ° C or higher for 50 to 200 hours. Therefore, disinfection is performed for about one month in summer. When the soil temperature is 50 ° C. or higher, an integration time of 50 hours is sufficient. Since solar heat is transferred from the surface of the soil, thermal conductivity is an important factor and the moisture content of the soil must be adequate. Usually, the water content must be increased by pouring water.

[0006]

In solar heat disinfection, since solar heat is transmitted only from the surface of the soil, even if the temperature in the house rises to 70 ° C or more in the daytime, the soil temperature will be at most 40 cm or more from 20 cm above the ground surface. Soil as deep as possible cannot be disinfected and has the disadvantage of ineffectiveness. Therefore, 20
Since soil deeper than a centimeter is not disinfected, if it is deeply plowed and fertilized or ridged after solar heat disinfection, it will be mixed with soil that is not disinfected, and the effect will be lost. Therefore, it is necessary to apply fertilizer and ridge before heat disinfection. Further, in a low temperature area such as Hokkaido, the temperature is not sufficiently increased, and the effect is small.
In addition, disinfection cannot be performed if the summer temperature is high.
In addition, water must be injected before disinfection to increase the thermal conductivity of the soil.

[0007]

According to the first aspect of the present invention, there is provided a method for heat disinfection of soil according to the present invention, wherein a pipe is buried in soil in a house, and the soil is heated by passing hot water or hot liquid through the pipe. In the summertime, the soil temperature is increased by using the apparatus in combination with solar heat and ground heating to increase the temperature of the soil. In other words, while conventional soil disinfection using only solar heat only performs soil disinfection within 20 cm from the surface of the ground, the combined use of solar heat and underground heating heats both from the surface of the soil and from the ground, and it is more than 20 cm from the surface of the soil. Heat disinfection of the soil. The method for disinfecting soil according to claim 6 uses underground heating in which a porous pipe is buried in the soil in the house, and high-temperature air is supplied into the soil from the hole of the pipe to warm the soil. In addition, the soil temperature is raised by using the solar heat and the underground heating together to perform the heat disinfection of the soil.

At this time, the soil on the buried pipe is completely disinfected by setting the burying depth of the pipe to 40 cm to 80 cm. Further, as described in claim 4, hot water or hot liquid in
By setting the temperature to not lower than ℃, the soil on the pipe can be easily maintained at not lower than 40 ° C. According to the fifth aspect of the present invention, the soil is subjected to heat disinfection in summer and the soil is heated by passing hot water or hot liquid through a pipe in winter to promote the growth of crops or extend the growth period. According to the tenth aspect of the present invention, soil is disinfected by heat in summer, and high-temperature air is supplied from a pipe in winter to warm the soil, thereby promoting the growth of crops or extending the growth period. . Here, summer is a period when sunlight is strong and the outside air temperature is high and solar heat can be disinfected.
September and October are also eligible. The winter season is a time when the outside air temperature is low and the growth of crops is promoted by heating the soil. In cold regions, the target period is March, April, May, October and November.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a method for heat disinfection of soil according to the present invention.
This will be specifically described with reference to an underground heating device schematically shown in FIG. For heat disinfection in the summer, hot water or hot liquid of 70 ° C. or more is produced by a boiler 1 using oil or gas as a heat source, and is housed in a house 2 or a tunnel (not shown) from a surface 5 of the soil 4 to 40 cm to 80 cm. Pass through a plurality of buried pipes 3. Usually, the mulch 6 is used in combination with the house 2 or the tunnel, but the mulch is not necessarily required when the solar heat from the sunlight 7 is sufficient or in an area.

The hot liquid is usually an aqueous solution of ethylene glycol or propylene glycol and has a boiling temperature of 10
Boiling is prevented even when the temperature is increased to 0 ° C. or higher, and freezing is controlled to -40 ° C. or lower to prevent freezing when the boiler is not used in winter. Hot water is used in areas where there is no concern about freezing. As the pipe 3, an iron pipe, a plastic pipe, or the like is used. Usually, a cross-linked polyethylene pipe is used. Each pipe 3 usually has an outer diameter of 13 mm to 26 mm and an interval of 30 cm to 100 cm.
Buried in A control valve (not shown) is provided for each ridge or every several ridges of the pipe 3 to adjust the flow rate of hot water or hot liquid flowing through the pipe.

It is more effective to lay a heat insulating material (not shown) under the pipe so that heat from the pipe does not escape downward from the pipe. In underground heating in winter, the temperature of the hot water or hot liquid from the boiler does not need to be very high, at most 50 ° C. A temperature sensor is provided at a position of 20 cm underground, and the flow rate in the pipe is adjusted so that the temperature of 20 cm underground becomes 18 ° C. to 25 ° C. The air in the house may be heated by a hot air heater, but the growth condition of the crop is good as long as the underground temperature is maintained without heating the air.

[0012] The temperature of the soil near the pipe is close to the temperature of hot water or hot liquid, which has an adverse effect on the roots of the crop. By setting the depth of the pipe from 40 cm to 80 cm, the root of the crop is separated from the position of the pipe, so that the crop is not adversely affected. The burial depth of the pipe is 40cm
By setting the height to 80 cm, the pipe is not damaged by the cultivator during plowing.

[0013]

EXAMPLE The heat disinfection method for soil of the present invention was carried out in Hokkaido, where solar heat is weak even in summer and solar heat disinfection is impossible. A mulch is laid in a house with an area of 150 m ² ,
Using an underground heating device in which two crosslinked polyethylene pipes having an outer diameter of 13 mm were buried at a depth of 60 cm in the ground and one ridge was buried, an ethylene glycol aqueous solution was heated to 80 ° C. with a boiler, and the soil was heated by flowing through the pipes.

The air temperature at a height of 1.5 m inside the house rose to a maximum of 73 ° C., but the minimum air temperature at night was 30 ° C. or less. After 20 days, the soil temperature at a depth of 60 cm in the ground was a maximum of 40 ° C. and a minimum of 38 ° C., and the soil temperature at a depth of 20 cm in the ground was a maximum of 51 ° C. and a minimum of 45 ° C. In this state, all the soils within a depth of 60 cm have not reached 40 ° C. or more. After 30 days, the soil temperature at a depth of 60 cm in the ground is a maximum of 46 ° C. and the minimum is 45 ° C., and the soil temperature of a depth of 20 cm in the ground is a maximum of 53 ° C. and a minimum of 46 ° C.
° C. In this state, the temperature of all soils within a depth of 60 cm is 45 ° C., and heat disinfection is completely performed.

During this period, the maximum outside temperature was 30.8 ° C. for one day, but the average maximum temperature was 25 ° C.
The average minimum temperature is 16 ° C., and solar heat disinfection using only normal solar heat is impossible. In addition, the soil temperature within 60 cm was 40 degreeC or more for 10 days after stopping the underground heating. Kerosene consumption during this period was 230 l. In the underground heating system, the cultivation period of melon is extended by heating the soil in winter.

As an embodiment of the method for heating the soil,
In addition to passing hot water or hot liquid through the buried pipe, a method is also possible in which a porous pipe is buried in soil, high-temperature air is passed through the pipe, and high-temperature air is supplied into the soil from the hole of the pipe. . As the porous pipe, a pipe made of a synthetic resin and provided with holes of about 1 mm in diameter at an interval of 5 to 10 cm, or a porous pipe of sintered metal or the like is used.

The temperature of the high-temperature air is usually 70 ° C. or higher for solar heat disinfection in summer, and the temperature of the high-temperature air is preferably about 50 ° C. for underground heating in winter. If high-temperature air is supplied into the soil, the air rises toward the surface of the ground, so that there is little heating under the buried pipe, which is economical. Also, in the underground heating in winter, warm air escapes into the house through the ground and does not need to warm the air in the house. Further, since air is supplied to the soil, oxygen is sufficiently supplied to the soil, which is suitable for microorganisms and plant roots in the soil.

[0018]

According to the heat disinfection method for soil of the present invention, it is possible to effectively heat the ground to a temperature at which pathogens inhabiting the soil can be effectively eradicated. Furthermore, the method for disinfecting soil of the present invention can completely avoid disinfection of soil by chemicals, and is a very effective method for disinfecting soil as a measure against environmental pollution.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram schematically showing an underground heating device.

[Explanation of symbols]

1. Boiler 2. House 3. Pipe 4.
Soil 5

Claims (10)

[Claims] 1. An underground heating system for burying a pipe in the soil in a house and warming the soil by passing hot water or hot liquid through the pipe, and raising the temperature of the soil by using both solar heat and ground heating. A method for heat disinfection of soil, wherein heat disinfection of soil is performed. 2. The method for heat disinfection of soil according to claim 1, wherein the burial depth of the pipe is 40 cm to 80 cm from the surface of the ground. 3. The method for heat disinfection of soil according to claim 2, wherein the burial depth of the pipe is 60 cm from the surface of the ground. 4. The method for heat disinfection of soil according to claim 1, wherein the supply temperature of the hot water or hot liquid during soil disinfection is 70 ° C. or higher. 5. An underground heating device for burying a pipe in the soil in a house and warming the soil by passing hot water or hot liquid through the pipe, and using a combination of solar heat and ground heating in summer to control the temperature of the soil. A soil heat disinfection method by raising the temperature of the soil, and in the winter, the soil temperature is increased by underground heating to perform underground heating. 6. An underground heating system in which a porous pipe is buried in soil in a house, and high-temperature air is supplied into the soil from a hole of the pipe to heat the soil, thereby providing solar heat and ground heating. A method for heat disinfection of soil, wherein the temperature of the soil is raised by combined use to heat disinfect the soil. 7. The method for heat disinfection of soil according to claim 6, wherein the burial depth of the pipe is 40 cm to 80 cm from the surface of the ground. 8. The method for heat disinfection of soil according to claim 7, wherein the burial depth of the pipe is 60 cm from the surface of the ground. 9. The supply temperature of hot air at the time of disinfecting soil is 70.
The method for heat disinfection of soil according to claim 6, 7 or 8, wherein the temperature is not lower than ℃. 10. An underground heating system in which a porous pipe is buried in soil in a house, and high-temperature air is supplied into the soil from a hole of the pipe to heat the soil, and the solar heat and the underground heat are applied in summer. A method for heat disinfection of soil, characterized in that the soil temperature is increased by heating the soil in combination with heating, and the soil temperature is increased by heating the ground in the winter in the winter.