Method for cultivating asparagus and liquid mulch agent used in said cultivation method

Abstract

To prevent asparagus plants from being infected with stem blight in asparagus cultivation in which new shoots sprouting from rhizomes and growing to a prescribed length are harvested. [Solution] In early spring, a first liquid mulching agent is sprayed onto a field where asparagus rhizomes grow, covering it with a black covering film, and then, when the asparagus is harvested and the stalks and leaves of the cultivated plants reach erection, a second liquid mulching agent is sprayed onto the field and covered with a white covering film, thereby suppressing a rise in ground temperature and promoting the growth of strong rhizomes, while also preventing the stems of the cultivated plants from contracting stem blight disease due to mud splashes containing pathogens adhering to them during rainfall.

Description

[Technical field]

[0001] The present invention relates to a method for cultivating asparagus, which is an edible vegetable, and to a technical field of a liquid mulching agent used in said cultivation method. [Background technology]

[0002] Asparagus is generally known as a vegetable, and is classified as a member of the genus Asparagus in the family Asparagaceae. Like many vegetables (plants), new shoots sprout (germinate) when seeds are sown, and these shoots grow and the stems elongate. However, the shoots that sprout from the sown seeds are not harvested and eaten when they grow to a harvest height (for example, 25 cm). Rather, after sowing, the shoots sprout and become erect, repeatedly, for example, for about two years, to promote the growth of the underground stems (underground stocks, root stocks). Then, from the spring of the third year, new shoots that have accumulated nutrients and grown from the underground stems sprout (germinate), and the young stems that have grown to the harvest height are harvested, and the harvested stems are sold on the market as asparagus. This type of asparagus can continue to produce stems for many years (10 to 15 years) from the third year after sowing, but in order to do so, the new shoots that germinate from the sown seeds are allowed to grow large and cultivated into plants without being harvested in the year they are sown.The upright stems then grow luxuriantly, and the nutrients produced by photosynthesis in the stems and leaves accumulate there, over the year as underground stems. In the second year, the asparagus is harvested as an underground stem that has accumulated nutrients and continues to grow without being harvested. After the third year, for example, in the Kanto region, as shown in FIG. 4, the spring bud harvesting period continues from April to May, in which the shoots that begin to sprout in early spring from February to March are cut and harvested when they reach a certain height. After that, the standing stem period is from May to June, during which strong shoots are selected and allowed to grow without being harvested to become mother stems with fine stems and leaves. During the standing stem period, the nutrients generated by the leaves of the standing stems through photosynthesis are accumulated in the underground stems, and after the standing stem period, the summer bud harvesting period is from October to November, during which new shoots continue to sprout from the underground stems that continue to accumulate nutrients through the standing stems, and as autumn deepens, the underground parts die, while the underground stems overwinter with accumulated nutrients. By repeating this cycle, asparagus is a vegetable that can be harvested repeatedly for many years, as mentioned above. Stem blight is known as one of the most serious diseases in cultivating asparagus. The pathogen of stem blight (Diaporthe asparagi (Phomopsis asparagi)) is a type of filamentous fungus. When the pathogen of stem blight attaches to the stem of an upright stem and infects it, the infected area turns light brown. As the infection progresses, black (blackish brown) spots appear on the infected area, and these spots are called pycnidia. In the pycnidia, countless conidia that become pathogenic bacteria are produced, and when the conidia grow to their full size and break, the conidia are scattered into the air. It is said that some of the scattered conidia attach to other stems, causing them to become infected with stem blight, leading to the spread of stem blight (secondary infection). On the other hand, some of the scattered conidia fall into the field and overwinter in the soil. These overwintered conidia become the pathogenic bacteria for stem blight the following year, which causes the spread of stem blight to occur almost every year, causing great damage to the healthy cultivation of asparagus. A wide variety of control methods and agents (disinfectants) have been developed and put to practical use against stem rot disease. For example, among the control agents, it has been reported that benomyl hydrate and TPN (chlorothalonil) hydrate are suitable for control, and that effective control can be achieved by combining the methods against primary and secondary infections (see, for example, Non-Patent Document 1). However, as mentioned above, asparagus is cultivated repeatedly over many years, and therefore when the above-mentioned control methods using control agents are used, not only do the pathogens acquire resistance to the agents due to repeated use over many years, gradually weakening the control effect, but also the control agents remain in the environment for many years, posing the risk of adversely affecting the ecosystem, becoming a social problem. Furthermore, there have been proposals to control the pests by growing them in greenhouses or by burning the nursery stalks with a burner after cutting them in the fall. However, the current situation is that it is difficult to deal with this issue, as it would require a huge financial burden to install and maintain the equipment required for greenhouse cultivation, and it is difficult to maintain the control effect within the greenhouse.

[0003] On the other hand, asparagus is a plant that has the optimum growth temperature of 10 to 30 degrees Celsius and is somewhat resistant to dryness. When cultivating this vegetable, black mulch sheets (film mulch) are sometimes laid on the field surface (furrow surface) in early spring to promote early germination, and when this is applied to the cultivation of asparagus, as mentioned above, new shoots sprout from underground stems, so it is not possible to determine in advance where the new shoots will emerge. For this reason, when a mulch sheet is laid, it is virtually impossible to identify the position of sprouting new shoots in advance and perform the drilling work, so it is necessary to remove (peel off) the mulch sheet when the time for new shoots to sprout is judged.However, if the time for removal is misjudged and the removal is done too early, the ground temperature will drop and the sprouting of new shoots will be delayed.In addition, the removed mulch sheet will become waste plastic and must be disposed of as industrial waste, which not only makes the work difficult but also raises the expected adverse impact on the environment associated with disposing of the mulch sheet as industrial waste. In view of this situation, liquid mulching agents have been developed and put to practical use (see, for example, Patent Document 1). This liquid mulching agent is a black liquid with biodegradability, and when it is sprayed on a field, it forms a black coating film that is spread over the entire field surface, so that it is expected to have a high mulching effect, but the coating film is easily broken by the growth force of the sprouting sprouts, and has the advantage that it does not hinder the sprouting and growth of asparagus. Therefore, unlike mulching sheets, the coating film of the liquid mulching agent does not need to be removed in response to the sprouting of sprouts, and can be left in the coating state, so that even in the early spring after the sprouts have not yet risen sufficiently in temperature, it contributes to an increase in ground temperature, promoting subsequent sprouts and the growth of standing stems. Moreover, the coating film of the liquid mulching agent biodegrades over time and disappears as a nutrient, so there is an advantage that no chemical damage occurs. The pathogenic fungus that causes stem blight reproduces when the temperature is between 20 and 30 degrees Celsius, and it is said that the optimum temperature for reproduction is around 25 degrees Celsius. As if to prove this, it has been confirmed that there is little incidence of stem blight during the spring bud harvest period in early spring when the temperature has not yet risen. However, it has been confirmed that the number of cases of stem blight increases sharply after the temperature rises after May and the stems become erect, and there is a tendency for the number of cases to increase especially after rainfall. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Nagasaki Prefectural Agriculture and Forestry Technology Development Center Research Report No. 10: pp. 31-50 (2020) "Integrated control of stem blight in semi-forcing asparagus" [Patent documents]

[0005] [Patent Document 1] JP 2004-313048 A Summary of the Invention [Problem to be solved by the invention]

[0006] By the way, when we continued to grow asparagus in fields coated with the above-mentioned liquid mulch agent, we found that in the fields where stem blight had occurred the previous year, in the early stages when temperatures were below 25°C, only a few cases of stem blight were confirmed on the upright plants, and asparagus could be harvested without any problems, but later, when temperatures approached 25°C, we found that the incidence of stem blight on the upright plants rapidly increased. This was because the pathogenic bacteria of stem blight, which became active (activated) as the temperature approached 25°C, were dispersed into the air (pathogens were also dispersed from other fields where stem blight had occurred), and attached to the stems and leaves of the upright plants, causing the disease. As mentioned above, the reason why the increase in the incidence of the disease after rainfall has been confirmed is thought to be that pathogens in the soil mixed with muddy water that occurs during rainfall such as the rainy season or evening showers repeatedly attach to the stems of upright plants, causing the stems and leaves of upright plants to become infected with stem blight, which then spreads to the leaves. It is therefore necessary to address this issue, and to do so, it is first necessary to take measures to prevent the soil temperature from rising to maintain the growth of the rhizomes, as well as to prevent the adhesion of muddy water during rainfall, which can contain pathogens in the soil.Furthermore, it is necessary to prevent pathogens from being dispersed into the air or mixed with muddy water during rainfall from adhering to the cultivated plants, and to prevent the dispersion of conidia when the formed conidial hyphae are destroyed.These problems are the subject of the present invention. [Means for solving the problem]

[0007] The present invention has been created in view of the above-mentioned circumstances and with the objective of solving these problems. The invention of claim 1 is a method for cultivating asparagus in which new shoots sprout from asparagus rhizomes in a field grow, and the young stems that reach harvest height are cut and harvested, and the method comprises the steps of: applying a black pigment to the asparagus rhizomes in early spring before the new shoots sprout from the rhizomes; , both of which are biodegradable polymer emulsions and dispersants Mainly composed minutes and A first liquid mulching agent containing the white pigment is sprayed on a field, and asparagus is cultivated in the field covered with a black coating film. Thereafter, when the temperature rises and the asparagus stands, , both of which are biodegradable polymer emulsions and dispersants Mainly composed minutes andand spraying a second liquid mulching agent containing the compound as a white covering film onto a farm field, and continuing to cultivate asparagus in the farm field covered with the white covering film. The invention of claim 2 is the method for cultivating asparagus according to claim 1, characterized in that the second liquid mulch agent is sprayed when the air temperature is between 18°C ​​and 25°C, preferably 22°C. The invention of claim 3 is a method for cultivating asparagus as described in claim 1, characterized in that the second liquid mulching agent is sprayed to include the stems and leaves of the cultivated plants, and the surfaces of the stems and leaves are coated with a coating film of the second liquid mulching agent. The invention of claim 4 relates to the method for cultivating asparagus according to claim 3, characterized in that the covering height of the second liquid mulching agent on the surfaces of the stems and leaves is 5 cm or more from the field surface. The invention of claim 5 is the method for cultivating asparagus as described in claim 3, characterized in that the second liquid mulching agent may be repeatedly sprayed onto the field, and the repeated spraying of the second liquid mulching agent is performed at a stage when 1 / 4 or more of the coating film of the second liquid mulching agent previously sprayed has disappeared. The invention of claim 6 is characterized in that the coating of the second liquid mulching agent on the stems and leaves may be repeated other than when the second liquid mulching agent is repeatedly sprayed on the field, and the repeated coating of the second liquid mulching agent on the stems and leaves other than when the second liquid mulching agent is repeatedly sprayed on the field is performed by spraying or applying the second liquid mulching agent on the stems and leaves. 5 The method for cultivating asparagus is as described above. The invention of claim 7 is a liquid mulch agent used in the asparagus cultivation method described in claim 1, characterized in that the first liquid mulch agent is a black suspended emulsion aqueous solution whose main components in addition to a black pigment are a polymer emulsion and a dispersant, both of which are biodegradable, and the second liquid mulch agent is a white suspended emulsion aqueous solution whose main components in addition to a white pigment are a polymer emulsion and a dispersant, both of which are biodegradable. The invention of claim 8 is a liquid mulch agent used in the asparagus cultivation method according to claim 7, characterized in that at least one type of chemical selected from a herbicide or a fungicide is mixed into the first liquid mulch agent and / or the second liquid mulch agent. Effect of the Invention

[0008] According to the invention of claim 1, in cultivating asparagus in which new shoots sprouting from the rhizomes reach harvest height and are then cut off, a first liquid mulching agent is sprayed in early spring before the new shoots sprout from the rhizomes, covering the field surface with a black coating film, thereby promoting early germination of new shoots as the soil temperature of the field rises, thereby improving the spring bud harvest, and then, when the temperature rises and the stalks stand, a second liquid mulching agent is sprayed to cover the field surface with a white coating film. By keeping the fields covered with the first and second liquid mulch, it is possible to suppress the rise in ground temperature during the summer bud harvesting period, promote healthy sprouting of the summer buds, and achieve a high harvest.However, because the field surface is covered with the first and second liquid mulch agents throughout the spring and summer harvesting periods, this prevents (reduces) the pathogens of stem blight that are present in the soil (and have overgrown) from mixing with muddy water that splashes during rainfall, reducing the chances of erect plants becoming infected with stem blight and allowing for stable cultivation of asparagus. By adopting the invention of claim 2, the second liquid mulch agent is sprayed when the air temperature is between 18°C ​​and 25°C, preferably 22°C, so that the rise in ground temperature can be suppressed before the temperature reaches 25°C, at which point the pathogenic bacteria of stem blight become active, thereby making it possible to prevent infection with stem blight. By applying the invention of claim 3, the second liquid mulching agent can be sprayed up to the stem and leaf portions of the upright stems, so that the surfaces of the stems and leaf portions can be covered with a coating film of the second liquid mulching agent. As a result, even if muddy water mixed with the pathogenic bacteria of stem blight adheres to the stems and leaf portions of the cultivated plants, the stems are covered with a coating film of the second liquid mulching agent, preventing the pathogenic bacteria from adhering to the stems and leaf portions, thereby suppressing the infection of stem blight. By adopting the invention of claim 4, the coverage height of the stem and leaf surface with the second liquid mulch agent is 5 cm or more from the field surface where mud splash water is likely to adhere, thereby effectively preventing infection via mud splash water. By adopting the invention of claim 5, during the long summer bud harvesting period, the second liquid mulching agent may be repeatedly sprayed onto the field. In this case, the repeated spraying of the second liquid mulching agent will be carried out at a stage where 1 / 4 or more of the coating film of the second liquid mulching agent sprayed previously has disappeared. As a result, the field surface will continue to be covered in a white state by the second liquid mulching agent, which will not only suppress the rise in ground temperature but also greatly contribute to preventing the infection of stem blight. By adopting the invention of claim 6, the coating of the stems and leaves with the second liquid mulching agent may be repeated other than when the second liquid mulching agent is repeatedly sprayed in the field. In this case, the repeated coating of the stems and leaves other than the repeated spraying of the second liquid mulching agent in the field is carried out by spraying or applying the second liquid mulching agent to the stems and leaves, so that the coating of the stems and leaves with the second liquid mulching agent can be carried out efficiently. By adopting the invention of claim 7, the first liquid mulch agent is a black suspended emulsion aqueous solution whose main components are a polymer emulsion and a dispersant, both of which are biodegradable in addition to the black pigment, and the second liquid mulch agent is a white suspended emulsion aqueous solution whose main components are a polymer emulsion and a dispersant, both of which are biodegradable in addition to the white pigment, so that the first and second liquid mulch agents can easily be made biodegradable. By adopting the invention of claim 8, at least one type of chemical selected from a herbicide or a fungicide is mixed into the first liquid mulching agent and / or the second liquid mulching agent, so that the herbicide or fungicide can be sprayed in addition to covering the field, improving workability. [Brief description of the drawings]

[0009] [Figure 1] This is a table showing the results of measuring soil temperature in early spring in a field where mulch film was laid, a field where the first liquid mulch agent was sprayed (test area), and an untreated field where nothing was applied (control area). [Diagram 2] FIG. 1 is a table showing the harvest status of asparagus per rhizome in a field (test area) where the first liquid mulch agent was sprayed and in a field (control area) where nothing was applied, with and without irrigation. [Diagram 3] This is a table showing the state of stem wilt disease in experimental ridges (test areas) where a first liquid mulch agent was sprayed and stems were allowed to stand, and in blank ridges (control areas) where no spray was given, after which a second liquid mulch agent was sprayed. [Figure 4] FIG. 1 is a graph showing the cultivation status of asparagus over a one-year period. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] As mentioned above, asparagus is a perennial plant with underground stems, and when focusing on stem blight, it has the advantage that, when cultivated in a healthy field where the disease is not present, it can be harvested for a long period of 10 to 15 years from the third year after sowing. The cause of stem blight occurring in such a healthy field is that the pathogen that grows in other fields where stem blight is occurring (the breeding ground of stem blight) is carried to the healthy field by being blown in by the wind, or by running water from the breeding ground caused by the attack of heavy rain such as a typhoon, and when the pathogen that is carried in this way attaches to the cultivated asparagus stalks, it infects and develops the disease in the weak resistance parts of the cultivated stalks, and the parts that show the light brown disease gradually spread as the infection spreads. Black speckled pycnidia are produced in the diseased areas, and when the pycnidia are destroyed, the pathogenic conidia are dispersed into the air. In this way, a healthy field becomes infected with stem blight (primary infection), which then causes the disease to spread (secondary infection) in the field, and this spread is repeated over the years. As a countermeasure against this type of stem blight, the pathogenic fungus of stem blight is said to grow at temperatures between 20℃ and 30℃. In order to prevent the onset and spread of stem blight, Elimination of pathogens in the field before new shoots emerge - Suppression of the adhesion of pathogens to the upright stems and leaves due to muddy water splashed during rainfall Inhibition of the growth of infectious pathogens - Suppression of the adhesion of pathogens carried from other infected fields These are important issues, and the specific objective of the present invention is to address even one of these issues so as to eliminate or minimize the need for spraying pesticides.

[0011] The present invention provides a cultivation method using a liquid mulching agent to combat stem blight of asparagus, and a liquid mulching agent for use in said cultivation method. The liquid mulching agents used here are a first liquid mulching agent and a second liquid mulching agent, and of the main components used in either liquid mulching agent, it is preferable to use those that are biodegradable and harmless (non-toxic) to animals and plants other than pigments, and that, as a result of being biodegradable, do not accumulate in the field over time and are absorbed as nutrients by plants. The first liquid mulch agent contains a black pigment as its main component, so when it is sprayed on the field, it forms a black gel-like coating film that is laid down in sheet form on the field surface, whereas the second liquid mulch agent contains a white pigment as its main component, so when it is sprayed on the field, it forms a white gel-like coating film that is laid down in sheet form on the field surface. The covering film formed by spraying the first and second liquid mulch agents on the furrow surfaces at different times is easily broken through by the sprouting power (growth power) of the new shoots that sprout from the asparagus rhizomes in the field, and the presence of the covering film does not affect the sprouting or growth of the new shoots.

[0012] The first liquid mulching agent is sprayed on the ridge surface in early spring before new shoots sprout from the underground stems, so that a coating film of the first liquid mulching agent is formed over the entire ridge surface so that no soil is exposed, just as if it were covered with an existing mulch film. In a field on which a coating film of the first liquid mulching agent has been formed in this manner, since the coating film of the first liquid mulching agent is black, it absorbs sunlight well in early spring when the soil temperature is not yet high enough, thereby exerting an excellent effect of raising the soil temperature, thereby activating the underground stems at an early stage and promoting the early sprouting of strong new shoots, as well as preventing the overgrowth of weeds. Incidentally, spraying the first liquid mulch agent on the field once is usually sufficient, but in cold regions such as Hokkaido, or in cases of cold damage where the temperature does not rise significantly even in early summer, it is possible to spray again after checking the disappearance of the coating film.

[0013] On the other hand, the second liquid mulching agent can be sprayed on the ridge surface even when the black coating film produced by spraying the first liquid mulching agent remains on the ridge surface before it completely disappears due to biodegradation, etc. The second liquid mulching agent is preferably sprayed at the time when the stem stands after the harvest in early spring, or around that time, when the temperature rises as early summer approaches, but if temperature is used as a guideline, it is preferable to spray it when the temperature approaches 22°C before reaching 25°C, which is said to be the temperature at which stem blight grows most. The second liquid mulch agent is sprayed so that the entire field surface, including the residue of the first liquid mulch agent, is not exposed, forming a sheet-like white coating film over the entire surface. In a field on which a coating film of the second liquid mulch agent has been formed in this manner, the coating film of the second liquid mulch agent is white, and so it reflects strong sunlight and suppresses the rise in soil temperature. This prevents the soil temperature from becoming too high for rhizome growth, which would inhibit proper growth of the rhizomes, and promotes the activation of the rhizomes, thereby promoting the emergence of strong new shoots and also preventing the overgrowth of weeds. The second liquid mulch agent is preferably sprayed repeatedly as necessary until the cultivated plants die or are removed in the fall, in which case it is preferable to spray the second liquid mulch agent when at least 1 / 4 of the coating film formed by the previous spray has disappeared, but it goes without saying that the second liquid mulch agent may also be sprayed when 1 / 4 or less has disappeared if necessary. In this case, the spraying may be performed on the area including the area where the coating film has disappeared in order to repair the area.

[0014] In this way, in the present invention, the first and second liquid mulching agents are sprayed on the asparagus growing field to form coating films, but since the second liquid mulching agent is related to the time of stem erection and stem blight mainly occurs on the stems and leaves of the erected plants, it is preferable that the coating film of the second liquid mulching agent is formed not only on the field surface but also on the stems and leaves. By forming a coating film on the stems and leaves of the erected plants, it is possible to prevent the adhesion of pathogenic bacteria to the stems and leaves due to mud splashes during rainfall, so when forming a coating film of the second liquid mulching agent on the stems and leaves, it is preferable that the height of the coating film is at least 10 cm from the field surface. When forming a coating film of the second liquid mulch agent on the stems and leaves of upright plants in this way, it is preferable from the viewpoint of workability to spray the second liquid mulch agent on the stems and leaves at the same time as spraying it on the field surface, but it may also be sprayed targeting the stems and leaves of upright plants. Furthermore, it may be applied to the stems and leaves of upright plants using an application means such as a brush or paintbrush. When a coating film of the second liquid mulch agent is formed on the stems and leaves of upright plants in this way, the coating film can prevent the attachment of pathogens of stem blight to the stems and leaves.

[0015] In addition, when stem blight is found on the stems and leaves of upright stems, it is preferable to form a coating film using the second liquid mulch agent on the surrounding areas including the diseased area. When the stems and leaves that have already developed the disease are coated with a coating film in this way, the proliferation of the pathogen and the generation of pycnidia can be suppressed, and even if the pycnidia that have developed are destroyed, the conidia cannot break through the coating film to escape, which contributes to preventing the dispersion of the pathogen and is expected to have a preventive effect on secondary infection.

[0016] The first and second liquid mulch agents used in the present invention are provided with a composition that contains a black or white pigment as one of its main components, a dispersant that has a surface-active function and prevents the pigment from settling within the liquid mulch agent, and a polymer emulsion that has the function of forming a coating film as its main component.

[0017] Examples of black pigments used in the first liquid mulching agent include carbon black, black iron, and charcoal powder, all of which are black in color and have no effect on the ecosystem, and at least one type selected from these pigments is used. On the other hand, examples of white pigments that can be used in the second liquid mulch agent include titanium oxide, zinc oxide, and lithopone, and titanium oxide is preferable as it passes the environmental substance standard test for biodegradable plastics.

[0018] Dispersants for these pigments are selected from among materials that are biodegradable and have no adverse effect on ecosystems even when biodegraded. Suitable examples of such dispersants include humates and polycarboxylates. Humates are black or dark brown in color and are biodegradable, making them suitable as dispersants for the first liquid mulching agent. Humates are alkali metal salts or ammonium salts of polymeric organic acids obtained by alkaline extraction of young coals, weathered coals, leonarites, peat, or peat, or polymeric organic acids obtained by oxidatively decomposing young coals, peat, or peat with nitric acid, and humates are alkali metal salts or ammonium salts of polymeric organic acids. The humic acid salt functions as a dispersant that prevents the black pigment from precipitating in the aqueous polymer emulsion solution. In this case, potassium salt and ammonium salt of humic acid are particularly suitable dispersants to be contained as active ingredients in the first liquid mulching agent, since they are classified as humic acid fertilizers under the Fertilizer Control Law.

[0019] On the other hand, as the main component of the second liquid mulch agent, dispersants that are black in color, such as the humate salt, are not preferred as they interfere with the formation of a white coating film, and therefore it is preferable to use as the dispersant a colorless or nearly colorless anionic surfactant that does not interfere with the formation of a white coating film. Such surfactants include: centre Examples of the surfactant include various surfactants such as carboxylic acid type, carboxylic acid type, acrylic acid type, sulfate type, and polyphosphate type, and at least one selected from these can be used.

[0020] Furthermore, one of the main components of the first and second liquid mulching agents is a biodegradable polymer emulsion, which has the function of forming a mulch film as a coating film on the ridge surface when sprayed on the ridge surface.The polymer emulsion adheres closely to the ridge surface where it is sprayed, forming a uniform coating film on the ridge surface.As the water content of this coating film decreases by evaporation or by being soaked into the soil, it becomes a coating that has appropriate water permeability, water resistance and breathability, and acts to prevent the field from drying out. Examples of such polymer emulsions include polyacrylic acid emulsions, polyacrylamide emulsions, polyvinyl acetate emulsions, and polycarboxylic acid emulsions, and at least one selected from these polymer emulsions can be used.

[0021] The first and second liquid mulch agents used to practice the present invention each contain a black or white pigment, a dispersant, and a polymer emulsion as the main components, and polyvinyl alcohol can be added as a thickening solvent, and an extender can be added as a pigment extender. In this case, an example of the extender pigment for the first liquid mulch agent is kaolin, and an example of the extender pigment for the second liquid mulch agent is calcium carbonate.

[0022] The present invention is a method for cultivating asparagus in a state where a coating film of a black liquid mulch agent and a white liquid mulch agent, the main ingredients of which are a biodegradable polymeric resin material and a black or white paint, is formed by spraying the liquid mulch agent at different times on a field where asparagus is grown. In this case, in order to remove pathogens remaining in the field cultivated the previous year, the field is subjected to a treatment for removing any remaining standing stems, if any, and a treatment for sterilizing the field by burning the field with a burner, etc., in early spring when there are no new buds sprouting, and also to treatments required for asparagus cultivation, such as spraying herbicides, fungicides, fertilizers, etc., which are normally used in asparagus cultivation, on the field as necessary.

[0023] Once these treatments have been thoroughly applied in the field, the first black liquid mulch agent is sprayed along the ridges. From the standpoint of ease of application, it is preferable to use a power sprayer to spray this first liquid mulch agent, and for this reason, the first liquid mulch agent is adjusted by adding water or the like so that it has a viscosity suitable for spraying with a power sprayer. The first liquid mulch agent thus sprayed dries naturally as the water evaporates and penetrates into the field, forming a soft black coating film on the field. In a field where a coating film of the black first liquid mulch agent has been formed, the field maintains high water retention while preventing the herbicide, fungicide, and fertilizer from being washed away by rainfall, while promoting an increase in soil temperature through daytime sunlight exposure in early spring and preventing a drop in soil temperature at night, ensuring soil temperatures of 15°C or higher, which is favorable for asparagus growth, even in early spring, promoting early germination of asparagus and enabling early shipment, leading to increased yields. Furthermore, as the soil temperature rises early in the spring, the growth of underground stems is promoted, making them strong and sturdy. The new shoots and upright stems that sprout from these roots also tend to be highly resistant (strong) to infection by pathogens, resulting in increased yields.

[0024] After the first black liquid mulch agent is sprayed in this way, the second white liquid mulch agent is sprayed, and the timing of spraying this second liquid mulch agent is when at least 1 / 4 of the coating film formed by spraying the first liquid mulch agent has disappeared. This disappearance of 1 / 4 or more varies depending on weather conditions such as rainfall, but it occurs approximately 1.5 to 3 months after the first liquid mulch agent is sprayed, usually at or around the time the stems stand. On the other hand, it has been reported that the optimum temperature for the proliferation (reproduction) of the pathogenic fungus of stem blight is around 25°C, so the timing of spraying the second liquid mulch agent can be selected when the temperature rises to 22°C. This period when the temperature reaches 22°C often coincides with the time when the stems stand, so this time can also be used as a guideline. The timing of spraying the second liquid mulch agent will depend on changes in weather conditions, and in seasons when the temperature rises quickly, it is recommended to spray it before the stems stand, as soon as the temperature approaches 22°C and before more than 1 / 4 of the coating film of the first liquid mulch agent has disappeared.On the other hand, in seasons when the temperature rises slowly, it is recommended to spray it after the stems stand and when more than 1 / 4 of the coating film of the first liquid mulch agent has disappeared. In this case, the remaining coating film of the first liquid mulch agent may or may not be removed, but from the standpoint of workability it is generally not removed. As with the application of the first liquid mulch agent, it is preferable to use a power sprayer to spray the second liquid mulch agent, and therefore it is preferable to adjust the viscosity of the second liquid mulch agent by adding water, for example.

[0025] In this way, the field where the second liquid mulch agent was sprayed is covered with a uniform viscoelastic white coating film. The field surface covered with this white coating film reflects sunlight, suppressing abnormal increases in soil temperature, and as mentioned above, maintaining an optimal growing environment for asparagus, which is sensitive to temperatures above 30°C. In this case, it is preferable to spray the second liquid mulch agent not only on the field but also on the stems and leaves of the standing plants. When the second liquid mulch agent is sprayed on the standing stems and leaves in this way, the stems and leaves are covered with a coating film of the second liquid mulch agent. As a result, the stems and leaves covered with the coating film are prevented from being contaminated by the pathogen of stem blight, and the infection of stem blight can be prevented. On the other hand, when the stems and leaves of the infected area are covered with the coating film afterwards, the contact with the outside air is closed, so the production of pycnidia in the infected area can be suppressed. In addition, even if the generated pycnidia are destroyed, the destroyed pycnidia are covered with the coating film, so the scattering of the pathogen can be prevented, which greatly contributes to preventing the spread of stem blight caused by secondary infection.

[0026] When covering the upright stalks with a coating film of the second liquid mulch agent, it is preferable to cover the stalks with a height of at least 10 cm from the field surface, which effectively prevents pathogens mixed with muddy water from the field surface from adhering to the parent stalks, especially during rainfall. The coating agent covering the parent stalks is attached to the vertical parts, so it tends to disappear earlier than the coating agent covering the field surface. In this case, the second liquid mulch agent may be sprayed again, or it may be applied using a coating material such as a brush or paintbrush. When spraying or applying the second liquid mulch agent to such parent stalks, if an infected diseased part is found during daily inspection, the second liquid mulch agent may be sprayed or applied to the parent stalk to form a coating film. When harvesting sprouts coated with a coating film of the second liquid mulch agent, the part that has grown above the coating may be cut and harvested.

[0027] The coating film of the second liquid mulch agent covering the field has a lifespan that varies depending on the thickness of the coating film, but is approximately the same as the lifespan of the first liquid mulch agent. Therefore, when the coating film of the second liquid mulch agent has disappeared to a certain extent, it is necessary to spray the second liquid mulch agent again to form a white coating film on the field surface. The timing of the second liquid mulch agent to be sprayed again is preferably when about 1 / 4 of the coating film of the second liquid mulch agent sprayed previously has disappeared, and preferably before the peak of summer. This is because by applying a white coating film of the second liquid mulch agent to the field surface again before the peak of summer, it is possible to prevent the ground temperature from rising during the peak of summer and reduce the weakening of the rhizomes due to high temperatures. If necessary, depending on the state of disappearance of the coating film of the second liquid mulch agent, a white coating film may be formed by spraying again.

[0028] When cultivating asparagus under the above conditions, it is essential to take the measures mentioned above to deal with stem blight. This applies to outdoor cultivation in the plains of the Kanto region, and it goes without saying that in cold regions such as the Tohoku and Hokkaido regions, or mountainous areas of Honshu, or in warm regions such as the Tokai, Shikoku, and Kyushu regions, appropriate changes to suit each region are necessary. Around January: Remove any remaining stalks from the previous year and clean up the field. Use a gas burner to sterilize the ground surface. Around February to March: Spray herbicides and fungicides on the field, then spray the black first liquid mulch agent to cover the entire furrow surface with a coating film of the first liquid mulch agent, which prevents the sprayed herbicides and fungicides from being washed away by rain, raises the soil temperature, maintains the water retention of the field, and promotes the activation of strong underground stems. Asparagus sprouts can be observed as early as this. From March to May: This is the season when stem blight is less likely to spread before the average temperature reaches 22°C. Covering the field with a coating film of the first liquid mulch agent increases the ground temperature and ensures that the field has good water retention. In an ideal growing environment for asparagus, strong, healthy new shoots that are resistant to pathogens such as stem blight sprout vigorously from the underground stems, which have grown strong. Asparagus can be harvested early by cutting the shoots that have grown to the required length early. May to June: After the initial harvest, the strong new shoots are allowed to stand, but at this time the temperature rises above 22°C, creating an environment in which the pathogenic bacteria of stem blight can actively grow. Before this happens, the second white liquid mulch agent is sprayed on the field to form a coating film of the second liquid mulch agent on the entire ridge surface. The white coating film reflects the sun's rays, suppressing the rise in soil temperature, protecting the underground stems, which are weak to high temperatures, preventing them from weakening, and promoting the growth of strong upright stems. The second liquid mulch agent is sprayed not only on the ridge surface, but also on the stems and leaves of the cultivated plants to cover the surface of the stems and leaves with a white coating film. - June to August: In the high temperatures of the fields, the growth of the cultivated plants slows down, and the underground stems grow using the nutrients produced by the photosynthesis of the grown cultivated plants, encouraging the germination of new shoots and making the plants ready for harvest. However, the soil is covered with a coating of the second white liquid mulch agent, which suppresses muddy water caused by rainfall during the rainy season and evening showers, preventing the pathogens of stem blight from attaching to the cultivated plants. In addition, for cultivated plants that have already been infected with the pathogens of stem blight and are showing symptoms, the production of conidia is suppressed. Even if the conidia grow and are destroyed, the pathogens can be prevented from scattering, providing a high level of prevention of secondary infection, allowing for a stable, continuous harvest of asparagus. From August to October: As asparagus can be harvested steadily, the white covering film will gradually disappear. When this happens, when about 1 / 4 of the ridge surface is exposed, spray the second liquid mulch on the ridge surface again, including the cultivated plants, to re-form the white covering film, which will suppress the spread of stem blight and promote photosynthesis in the cultivated plants, which will grow until late autumn and then die, and ultimately help cultivate strong underground stems in preparation for the following year.

[0029] Next, examples of the formulations of the components of the first and second liquid mulch agents will be described. First, as an example of a formulation for the first liquid mulch agent, when carbon black, humic acid, vinyl acetate emulsion, and poval are used as the components of the first liquid mulch agent, and kaolin is used as an extender pigment, the first liquid mulch agent is formulated as follows (unit: parts by weight). Carbon black: 100~1000 3-20% by weight humate solution: 1000-2000 Vinyl acetate emulsion: 3000~6000 10-20% by weight polyvinyl alcohol aqueous solution: 1000-2000 Kaolin: 500~2000 The method of producing the first liquid mulch agent using the thus formulated components is to mix carbon black into an aqueous solution of humic acid salts and disperse it in a mixer to obtain a slurry-like mixture. To this mixture, an aqueous polyvinyl alcohol solution is added and mixed well, and then a vinyl acetate emulsion is added and mixed. Kaolin is further added to this mixture and mixed, and the viscosity is adjusted with purified water to obtain a black first liquid mulch agent.

[0030] On the other hand, as an example of a formulation for the second liquid mulch agent, when titanium oxide, an anionic surfactant, vinyl acetate emulsion, polyvinyl alcohol, and calcium carbonate as an extender pigment are used as the components of the second liquid mulch agent, the second liquid mulch agent is formulated as follows (unit: parts by weight). Titanium oxide: 100~1000 3-20% by weight anionic surfactant aqueous solution: 400-1000 Vinyl acetate emulsion: 3000~6000 10-20% by weight polyvinyl alcohol aqueous solution: 1000-6000 Calcium carbonate: 500~2000 A specific method for producing the second liquid mulch agent is to mix titanium oxide (R-630, manufactured by Ishihara Sangyo Kaisha) into an aqueous solution of an anionic surfactant (Adekacol CS1361E, manufactured by Adeka Corporation) and disperse it in a mixer to obtain a slurry-like mixture. The polyvinyl alcohol aqueous solution is added to this mixture and mixed well, and then the vinyl acetate emulsion is added and mixed. Calcium carbonate (New Light F, manufactured by Nitto Funka Kogyo Co., Ltd.) is further added to this and mixed, and the viscosity is adjusted with purified water to obtain a white second liquid mulch agent. Experimental Example

[0031] Next, experimental examples of the present invention will be described together with comparative examples. <Creation of the first liquid mulch agent> A first liquid mulch agent was prepared according to the following formulation (parts by weight): Carbon black: 500 10% by weight humate solution: 2000 Vinyl acetate emulsion: 5000 10-20% by weight polyvinyl alcohol aqueous solution: 1500 Kaolin: 1000 As a specific method for producing the first liquid mulch agent using the above-mentioned prescribed components, carbon black (Mitsubishi Carbon MA100, manufactured by Mitsubishi Chemical Corporation) is mixed into an aqueous solution of humic acid salt (CH-03, manufactured by Terunite Co., Ltd.) while stirring with a mixer (stirrer) and dispersed with the mixer to obtain a slurry-like mixture. An aqueous solution of polyvinyl alcohol (28-98, manufactured by Kuraray Co., Ltd.) is added to this mixture and mixed well, and further vinyl acetate emulsion (Vinar EM232, manufactured by Kanae Chemical Industry Co., Ltd.) is added and mixed. Kaolin (Hard Mill, manufactured by Takehara Chemical Industry Co., Ltd.) is further added to this and mixed, and the viscosity is adjusted with purified water to obtain a black first liquid mulch agent.

[0032] <Creating the second liquid mulch agent> A second liquid mulch was prepared according to the following formulation (parts by weight): Titanium dioxide: 500 10% by weight anionic surfactant aqueous solution: 800 Vinyl acetate emulsion: 4000 10% by weight polyvinyl alcohol aqueous solution: 3000 Calcium carbonate: 1000 The specific method for producing the second liquid mulch agent using the above-mentioned formulated components is to mix titanium oxide (R-630 manufactured by Ishihara Sangyo Kaisha) into an aqueous solution of an anionic surfactant (ADEKACOL CS1361E manufactured by ADEKA CORPORATION) while stirring with a mixer (stirrer) and disperse it with the mixer to obtain a slurry-like mixture. The aqueous solution of polyvinyl alcohol is added to this mixture and mixed well, and the vinyl acetate emulsion is further added and mixed. Calcium carbonate (New Light F manufactured by Nitto Funka Kogyo Co., Ltd.) is further added to this and mixed, and the viscosity is adjusted with purified water to obtain a white second liquid mulch agent.

[0033] An asparagus cultivation experiment was conducted in asparagus fields in the plains of Chiba Prefecture using black No. 1 liquid mulch agent and white No. 2 liquid mulch agent.

[0034] <Experimental Example 1> - Confirmation experiment on the effectiveness of liquid mulch agents First, an experiment was conducted to examine the effectiveness of the above-mentioned blended black first liquid mulch agent. The field surface was burned and sterilized with a gas burner at the end of January. On a sunny day in mid-February, the first liquid mulch agent was diluted with tap water and applied to the field surface at a concentration of 500 g / m2. 2 The field was sprayed with a power sprayer (AP200, manufactured by Kyoritsu Co., Ltd.) so that the amount of application was 1000 mg / kg. As a comparative example, when the field was covered with a black polyfilm mulch (manufactured by Tsujino Plastics Co., Ltd.) having a thickness of 0.02 mm, two ridges were prepared for an open field where no treatment was performed, and after one week, the soil temperature in the soil at a depth of 15 cm from the ground surface was measured over time using a thermometer (temperature data logger, manufactured by T&D Co., Ltd.). The changes in soil temperature are shown in the table in Figure 1. In the table, since two ridges were tested for each, they are indicated as first liquid mulch agent I, II, polyfilm mulch I, II, and untreated I, II. These results confirmed that the first liquid mulch agent showed temperature changes comparable to those of conventional polyfilm mulch, and was particularly effective in preventing a drop in soil temperature at night. Subsequently, in the fields where polyfilm mulch had been applied, the polyfilm mulch was removed in anticipation of asparagus germination, and the soil temperature was found to have dropped, just as in the untreated field. It was confirmed that the use of first liquid mulch, which did not require the removal of the covering film, had a clear heat-retaining effect.

[0035] ○ Confirmation experiment of the effectiveness of the coating film of the first liquid mulch agent Next, in the same field as in Experimental Example 1, two test plots where the first liquid mulch agent was applied and two control plots where nothing was applied were further divided into irrigated and non-irrigated ridges, and the asparagus harvest situation was examined. In each ridge, 10 asparagus rhizomes (plants) were planted. The experimental period was from March to May, when the coating film with the first liquid mulch agent was effective, and the harvested asparagus was classified into seven ranks based on the thickness of each rhizome (plant), which are deemed to conform to the local asparagus shipping standards: "2L," "L thick," "L thin," "M," "S," "B" (low quality), and "non-standard." The average weight of asparagus for each rank was calculated (g / plant), and the sum of the average weights was calculated as the total weight (g). The results are shown in the graph in Table 2. Asparagus sprouts were confirmed from early March in the test area where the covering film of the first liquid mulch agent was formed, whereas in the untreated control area where no mulch agent was applied, asparagus sprouts were confirmed only in the latter half of mid-March. This was determined to be the result of the test area where the covering film of the first liquid mulch agent was formed having a superior effect on increasing soil temperature and retaining heat compared to the untreated control area, as confirmed in Experimental Example 1, and as a result, early sprouts were achieved.

[0036] As is clear from the graph in Table 2, the average weight of each rhizome of asparagus in the test plots coated with a film of the first liquid mulch agent was superior to the yield in the untreated control plot for most of the asparagus plants that were irrigated or not irrigated up to 2L to M size, confirming that the asparagus grown in the test plots coated with a film of the first liquid mulch agent was growing strong. When observing the difference between irrigation and non-irrigation, the average weight was heavier in the irrigated areas, confirming the importance of irrigation, but in the test plots where a coating film of the first liquid mulch agent was applied, even in the non-irrigated areas, the average weight was in most cases heavier for S size and above than for untreated irrigated and non-irrigated ridges. As a result, it was confirmed that in the test plots where a coating film of the first liquid mulch agent was applied, the water-retaining effect of the coating film came into play, and that even in the non-irrigated ridges, stronger asparagus could be harvested than in the untreated irrigated control plot. Furthermore, it was confirmed that the stems of asparagus growing in the ridges coated with the first liquid mulch agent were thicker than those in the untreated control area, had good leaf volume, and were growing into strong, well-developed plants.

[0037] Based on the above, in the test area coated with the first liquid mulch agent, the soil temperature rose to 15°C or more when exposed to sunlight, and the soil had an excellent moisture retention effect. As a result, during the seasons from March to May when the average temperature does not reach 22°C, it was confirmed that this promotes early germination of asparagus, and also enables the harvested asparagus to have thick stems with a strong, firm weight.

[0038] <Experimental Example 2> Next, the effect of the second liquid mulching agent in preventing stem blight was investigated. In this experiment, two additional ridges coated with a coating film of the first liquid mulching agent were prepared, and asparagus harvesting was stopped for these two ridges from mid-April to allow the sprouting shoots to stand. Then, in early May, when the shoots had sufficiently stood, the two ridges coated with the coating film of the first liquid mulching agent were divided into a test area where the remaining coating film of the first liquid mulching agent was removed and the second liquid mulching agent was sprayed to form a white coating film, and an untreated control area where the remaining coating film of the first liquid mulching agent was removed but no second liquid mulching agent was sprayed, and the disease state of stem blight was observed. The amount of the second liquid mulch applied to the experimental ridges was 1000g / m 2 The stems and leaves of the upright asparagus were also sprayed to a height of about 15 cm from the field surface and covered with a coating of the second liquid mulch agent. The occurrence of stem blight was then checked from late May to early August, and the results are shown in the table in Figure 3. Furthermore, when the second liquid mulch agent was sprayed, no occurrence of stem blight was observed in the parent plants growing in any of the ridges.

[0039] The table in Figure 3 shows the number of stems surveyed, the number of stems infected with stem blight, and the incidence rate for the test plot where the second liquid mulch coating was applied and the control plot, along with measurements of soil temperature (15 cm deep) on the corresponding survey dates. Here, the number of infected stems is the number of parent plants where disease is confirmed, and even if multiple diseased areas are found on one parent plant or the disease is large (over a wide area), the number of infected stems is counted as "1."

[0040] The above results show that from the time of observation in late May, approximately three weeks after covering with the second liquid mulch agent, the incidence of stem blight in the test plot was clearly lower than the incidence in the control plot, but the difference increased over time, and in early August the incidence in test row Y was 10.9%, while in the control plot it was 78.1%, more than seven times that amount, confirming that the test plot where the coating film of the second liquid mulch agent was formed was highly effective in suppressing the occurrence of stem blight. This is because, as shown in Experimental Example 1, in the spring when the plants are grown with a coating film of the first liquid mulch agent formed, the coating film of the first liquid mulch agent has the effects of raising the ground temperature, retaining heat, and retaining water, resulting in strong upright stems, and because the temperature is lower than the breeding temperature of the pathogen, the incidence of stem blight is kept low.However, the incidence of stem blight is still higher in the control area than in the test area.This is presumably because, depending on whether or not there is a coating film of the second liquid mulch agent, there is a large difference from an early stage in the degree to which the pathogenic bacteria of stem blight that live on the surface of the field attach to the cultivated plants due to mud splashes caused by rainfall, resulting in a difference in the incidence rate.

[0041] After that, in the test area where the white covering film was formed using the second liquid mulch agent, although the occurrence of stem blight could not be completely suppressed, it was confirmed that there was a clear difference in the incidence rate of stem blight compared to the control area where no treatment was applied. This is because the covering film was replaced from the black first liquid mulch agent to the white second liquid mulch agent, which prevented abnormal increases in soil temperature and provided waterproofing, protecting the temperature of the rhizomes and promoting healthy growth. Even if the pathogenic bacteria of stem blight growing in the field are dispersed into the air, the covering film is applied to the upright stems, suppressing the adhesion of the pathogenic bacteria dispersed into the air, not only suppressing the occurrence of the disease itself in the cultivated plants, but also suppressing the dispersion of the pathogenic bacteria due to the destruction of the conidial shells that are formed in the diseased areas of stem blight that have already occurred, thereby achieving a significant suppression effect not only on primary infection but also on secondary infection, allowing healthy cultivation of asparagus.

[0042] In this way, the present invention forms a covering film of the first black liquid mulch agent in the early stages of cultivation before germination, and then forms a covering film of the second white liquid mulch agent when the average temperature approaches 22°C.This allows for the growth of strong asparagus plants from early spring, allowing for a stable harvest from an early stage. As for the coating film of the second liquid mulch agent, by coating the surface of standing stems as well, it is possible to suppress not only the primary infection of stem blight but also secondary infection. This is expected to result in high harvests each year and to achieve a stable income by suppressing the onset of stem blight over many years.

[0043] Incidentally, the mulching method of the present invention has been described as being suitable for asparagus stem blight, but it is presumed to be effective against diseases caused by the same filamentous fungi as stem blight, such as powdery mildew, white rust, black brown disease, brown spot disease, black spot disease, anthracnose, rust, downy mildew, sooty mildew, gray mold disease, soft rot, sclerotinia rot, half-leaf ginkgo disease, and wilt disease. It is particularly effective for cucumbers and melons that are affected by vine blight disease, peppers, tomatoes, eggplants, etc. that are affected by leaf blight disease, and Cucurbitaceae, Fabaceae, Asteraceae, Poaceae, etc. that are affected by brown spot disease, and also for the genus Cercospora, which is affected by diseases in plants in general, and the genus Corynespora, which is affected by diseases in Fabaceae, etc., but these are to be left to future research. Furthermore, by making the biodegradable liquid mulch agent used in the present invention a colored liquid mulch agent by adding various colored pigments such as purple, blue, red, and green instead of black and white pigments, it is possible to prevent damage caused by pests that are repelled by specific colors, and it is also expected that the coloring of the field side parts of vegetables and fruits will be improved by receiving specific light (specific reflected light) from the field side. [Industrial Applicability]

[0044] The present invention can be utilized as a method for cultivating asparagus, which is an edible vegetable, and as a liquid mulch agent used in said cultivation method.

Claims

1. A method for cultivating asparagus, comprising the steps of: growing new shoots from asparagus rhizomes in a field; and harvesting the young stems by cutting them when they reach a harvest height; This method for cultivating asparagus is characterized in that in early spring before new shoots sprout from the underground stems, a first liquid mulching agent containing as main ingredients a black pigment, a biodegradable polymer emulsion, and a dispersant is sprayed onto the field, and asparagus is cultivated in the field covered with a black covering film, and then, when the temperature rises and the stems stand, a second liquid mulching agent containing as main ingredients a white pigment, a biodegradable polymer emulsion, and a dispersant is sprayed onto the field, and asparagus is continued to be cultivated in the field covered with a white covering film.

2. 2. A method for cultivating asparagus according to claim 1, characterized in that the application of the second liquid mulch agent is carried out at a time when the air temperature is between 18°C ​​and 25°C, preferably 22°C.

3. 2. The method for cultivating asparagus according to claim 1, wherein the second liquid mulching agent is sprayed on the stems and leaves of the cultivated plants, and the surfaces of the stems and leaves are coated with a coating film of the second liquid mulching agent.

4. 4. The method for cultivating asparagus according to claim 3, wherein the second liquid mulching agent is applied to cover the surfaces of the stems and leaves to a height of 5 cm or more from the field surface.

5. 4. The method for cultivating asparagus according to claim 3, characterized in that the second liquid mulching agent may be repeatedly applied to the field, and the repeated application of the second liquid mulching agent is performed when at least 1 / 4 of the coating film of the second liquid mulching agent previously applied has disappeared.

6. The method for cultivating asparagus as described in claim 5, characterized in that the coating of the stems and leaves with the second liquid mulching agent may be repeated at times other than when the second liquid mulching agent is repeatedly sprayed onto the field, and the repeated coating of the stems and leaves other than when the second liquid mulching agent is repeatedly sprayed onto the field is carried out by spraying or applying the second liquid mulching agent to the stems and leaves.

7. The first liquid mulch agent is a black suspension emulsion solution whose main components are a black pigment, a biodegradable polymer emulsion, and a dispersant. A liquid mulch agent used in the asparagus cultivation method according to claim 1, characterized in that the second liquid mulch agent is a white aqueous suspension emulsion solution mainly composed of a white pigment, a polymer emulsion, and a dispersant, both of which are biodegradable.

8. A liquid mulch agent used in the asparagus cultivation method according to claim 7, characterized in that at least one type of chemical selected from a herbicide or a fungicide is mixed into the first liquid mulch agent and / or the second liquid mulch agent.

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