Growth promotion method using light source that is installed in contact with base of cultivated plants during facility cultivation in coldest period, enabling localized heating and supplemental lighting at same time

Abstract

To provide a growth promotion method using a light source that simultaneously enables localized heating and supplemental lighting, which contributes to promoting photosynthesis and increasing yields in facility cultivation during a severe winter period, while reducing heating costs and workload for heating a facility.SOLUTION: A light source 5 is installed in contact with a base 4 of a cultivated plant 3 planted on a cultivation bench 1 and cultivation furrows 2. The light source 5 is a high-brightness light source that promotes photosynthesis in plants, and its surface temperature when emitting light is suitable for localized heating. By placing it in contact with the base of the plant and emitting light during the day, it can promote flower bud differentiation through heating and photosynthesis through supplemental lighting, thereby increasing yields and saving energy during facility cultivation during a severe winter period.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for promoting crop growth in greenhouse cultivation of flowers, vegetables, and the like, particularly during severe cold periods, by using a single light source to provide two functions: local heating and supplemental lighting, and by easily installing the light source. [Background technology]

[0002] In Japan, greenhouse-based flower and vegetable production has long been used for plant cultivation during the coldest months of the year. For example, in the case of forced strawberry cultivation, shipments begin after December, when prices are at their highest in the market, and various cultivation methods and strategies have been employed to ensure stable growth and yields. These include covering the substrate with mulch or straw for heat retention, and using heaters to maintain the temperature inside the facility. Maintaining vigor is crucial for strawberry forcing during the coldest months of the year. When the minimum temperature inside the cultivation facility drops below 5°C, the plants enter a dormant state. Furthermore, if the temperature remains below the critical growth limit for an extended period, the seedlings may wither. For this reason, the temperature inside the facility has generally been controlled using hot air heaters, but this is costly due to rising material and fuel costs. In recent years, methods have been developed to locally heat the base (crown) of strawberry plants using heat pipes, tape heaters, or electric heating wires.

[0003] Furthermore, during the coldest periods, due to low temperatures and low solar radiation, plants lack the light they need for photosynthesis. Supplementary lighting using a light source to make up for this shortage is also an effective means of cultivating plants during the coldest periods. Some prior art technologies, such as local heating devices and supplementary lighting devices, have been developed to solve the above-mentioned problems.

[0004] An example of a heating method using a heat pipe through which a heating liquid passes is disclosed in Patent Document 1. This invention proposes a cultivation tank in which a heat pipe is pre-installed and placed at the bottom of the crown, within the culture medium.

[0005] Patent documents 2, 3, and 4 also include inventions of a structure in which a light source is placed on a culture medium to illuminate the underside of leaves, in particular, in order to promote photosynthesis in plants. All of these devices demonstrate a certain level of effectiveness by irradiating light to the interior and lower parts of plant communities, areas that are normally not exposed to sunlight or other light from above. However, these devices are specialized only for heating and supplemental lighting, and have issues such as limited uses, high cost, and heavy installation work. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 5057352 [Patent Document 2] Japanese Patent Application Laid-Open No. 2002-272271 [Patent Document 3] Japanese Patent Application Laid-Open No. 2014-176374 [Patent Document 4] Japanese Patent Publication No. 2022-124073 [Non-patent literature]

[0007] [Non-Patent Document 1] "Strawberry Crown Temperature Control Demonstration Technical Manual, Selected for the FY2009 Research Results Practical Application Promotion Project," Kurihara Regional Agricultural Research and Extension Council, et al., pp.1 [Non-patent document 2] "Energy-Saving Production Management Manual for Greenhouse Horticulture (Revised 2nd Edition)", Ministry of Agriculture, Forestry and Fisheries, Production Bureau, pp.38-39 [Non-patent document 3] "Research Results Information for FY2021: Fertilization and Temperature Management Suitable for Cultivating "Echigohime" Strawberry with Crown Heating," Niigata Prefectural Agricultural Research Institute, pp. 8 [Non-patent document 4] "Fundamentals and Practice of Illuminated Cultivation", Edited by Hisamatsu Kan, National Agriculture and Food Research Organization, Floriculture Research Institute, pp.23-24, pp.166-167 Summary of the Invention [Problem to be solved by the invention]

[0008] According to the invention in Patent Document 1, an increase in yield can be achieved by placing a heat pipe in the culture medium and warming the area around the bottom of the strawberry plant's base (crown) with a heating liquid. However, since this involves introducing the strawberry cultivation tank itself, it is difficult to add it to an existing cultivation facility, and it is expected to be introduced into new cultivation facilities.

[0009] Other commonly used devices for crown heating include heat pumps alone, tape heaters, and electric heating wires. As with the invention of Patent Document 1, heat pumps require a dedicated boiler and heat exchange pipes that are placed in contact with the crown, which creates significant costs for equipment installation and construction. Tape heaters and electric heating wires also have issues with costs, such as electricity usage fees, and the installation work required. Furthermore, their only function is heating. After the heating period ends, an increased workload is expected, including removal work.

[0010] On the other hand, in the present invention, the only material used is a light source, which is simply placed on the cultivation ridges, so it can be used not only in existing cultivation facilities and elevated cultivation such as that seen in strawberry cultivation, but also in soil cultivation.In addition, it can continue to be used as a light source for supplementary lighting even after the heating period has ended.

[0011] According to the inventions of Patent Documents 2, 3, and 4, placing any light source on the culture medium so that it shines particularly on the underside of the leaves is effective in promoting photosynthesis and increasing yields of cultivated plants. While the effect of irradiating the underside of the leaves is well known, there is no mention of PPFD (Photosynthetic Photon Flux Density) in these light sources, and they do not have the ability to heat the base (crown) of the plant by placing it in contact with it, as shown in the present invention.

[0012] Furthermore, even if we focus solely on the use of high-intensity light sources with high PPFD values, while there are certainly light sources with high light intensity, most are installed on the ceiling or suspended from above by wires due to concerns about workability, heat generation, or the strong concept of overhead illumination. However, as is well known, the PPFD or light intensity of artificial light sources decreases the farther they are placed from the plant, thereby reducing their effectiveness. Furthermore, suspending light sources from above to get closer to the plants increases the distance, but this poses workability issues and, in greenhouses with combined solar and light sources, may block valuable sunlight from above. Regarding light source heat generation, for example, a heat-generating bulb typically reaches a surface temperature of 100 to 180°C, while a conventional LED reaches around 50°C. While LEDs themselves do not generate much heat, the temperature rises when resistors are used or when the voltage is increased to produce high light intensity. Exposing plants to such high temperatures can cause physiological disorders known as high-temperature damage, such as leaf burn and tip burn.

[0013] There are already several individual local heating devices and light supplement devices, and there are also plant cultivation systems and devices that combine them, but the growth promotion method described in this invention that uses a light source that allows for simultaneous local heating and light supplementation is novel and therefore does not yet exist.

[0014] The object of the present invention is to propose a method that can simultaneously provide localized heating and supplemental lighting to the base of the plant (crown), thereby promoting the growth of cultivated plants, especially during periods of severe cold, and contributing to workability and cost reduction. [Means for solving the problem]

[0015] The method of the present invention is characterized by the fact that, particularly in greenhouse cultivation during the coldest seasons, localized heating and supplemental lighting to the interior of the canopy can be achieved simultaneously by placing a light source in contact with the base (crown) of the cultivated plant. Furthermore, the method is characterized by the use of a high-intensity light source that has a surface temperature of 25°C to 28°C when emitting light and a high PPFD value.

[0016] Here, the base (crown) of the plant is often referred to as the crown in some cultivated plants, such as strawberries, which are used as representative examples in this invention, but it refers to the base of the plant in other cultivated plants. [Effects of the Invention]

[0017] The present invention has the following three advantages. (1) By placing the light source in contact with the base of the cultivated plant, it is possible to use the heat generated by the light to locally heat the plant, which contributes to maintaining plant vigor during severe cold periods, promoting flower bud differentiation, and increasing yields. (2) By irradiating the inside, bottom, and undersides of cultivated plants with a high-intensity light source as supplementary light, it compensates for the lack of photosynthesis caused by low solar radiation during the coldest period and bad weather, thereby increasing the amount of photosynthesis in the plants. (3) By using only light sources that combine the above two performance characteristics, installation is easy and workable. Furthermore, when LEDs are used as the light source, electricity consumption is significantly lower than with other light sources, reducing running costs and achieving energy-saving effects such as reducing heating consumption during the coldest periods. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a cross-sectional view of a light source installation according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] An embodiment of the present invention will be described below with reference to the drawings, taking strawberry cultivation as an example. FIG. 1 is a cross-sectional view of a light source installation according to an embodiment of the present invention. In the figure, 1 is a cultivation bench (cultivation stand) or the like, 2 is a cultivation ridge provided on the cultivation bench 1, and 3 is a cultivated plant, such as a fruit such as strawberries, a flower such as rose, chrysanthemum, or orchid, or a vegetable, planted in the cultivation ridge 2 provided on the cultivation bench 1. Regarding the cultivation bench 1 and the cultivation ridge 2, if the cultivated plant is planted outdoors (soil cultivation), no bench is used. However, in a cultivation method using an elevated cultivation bench or the like, soil, nutrient solution, etc. can be used in the cultivation ridge. 4 is the base (crown) of the cultivated plant 3, and 5 is the light source. The light sources 5 are placed in contact with the base (crown) 4 of the cultivated plants 3, and in order to provide localized heating and to irradiate the entire cultivated plant colony evenly, they are arranged in two rows in Figure 1 so that they hit all the bases (crowns) of the cultivated plants.However, as long as they can be placed in contact with the bases (crowns) 4, the number and positions of the light sources are not limited to this and can be adjusted to suit the cultivated plants.

[0020] The light source used in the present invention may be, for example, a high-pressure sodium lamp, a metal halide lamp, an incandescent bulb, a white fluorescent lamp, or an LED (light-emitting diode). However, due to the nature of the invention, a light source with a linear structure and that maintains a constant temperature throughout when emitting light is preferred. Furthermore, since the LED is to be installed at the base (crown) of a cultivated plant, taking into consideration waterproofing to withstand irrigation and high humidity, heat generation, flexibility, etc., an LED covered with a resin or the like is preferred. Furthermore, from the perspective of promoting growth, wavelengths containing red and blue light are desirable, but monochromatic red or blue light or the inclusion of other wavelengths is also acceptable. Furthermore, a light source with as high brightness as possible is preferred to promote photosynthesis. [Example]

[0021] The present invention is a method for promoting photosynthesis of cultivated plants, particularly during the coldest period in greenhouse cultivation, by using a high-intensity light source that is capable of simultaneously providing local heating and supplemental lighting.

[0022] Taking strawberries as an example, maintaining plant vigor during the coldest period is a key point in cultivation when forcing the crop for a long harvest period. When producing plants during the coldest period, symptoms such as difficulty maintaining plant vigor and leggy growth are generally observed due to a lack of photosynthesis caused by low solar radiation and low temperatures. Crown heating is an effective technique for promoting flower bud differentiation and the development of leaves and fruit clusters, thereby increasing the number of harvested fruit clusters. For this reason, various methods of crown heating have been attempted. However, crown heating can be expensive in terms of equipment costs and electricity bills.

[0023] [Crown heating] While this invention focuses only on heating during the coldest periods, there is also a well-known technique called crown temperature control, which involves heating in winter and cooling in summer. According to Non-Patent Document 1, strawberry crown temperature control technology was developed at the Kurume Research Station of the Kyushu Okinawa Agricultural Research Center (Independent Administrative Institution). This technique involves localized temperature control of the strawberry crown, promoting continuous budding and growth, thereby increasing yield. The crown contains the meristem, which is the site of important physiological phenomena related to flower bud differentiation and dormancy. Temperature control of this crown, i.e., heating during the cold winter months and cooling during the hot summer months, maintains the temperature at around 20°C, the optimum temperature range for flower bud differentiation and growth. This promotes fruit development in everbearing varieties and controls differentiation of the first axillary inflorescence (second flower) and beyond in everbearing varieties.

[0024] According to Non-Patent Document 2, the effect of crown heating alone is that energy-saving effects such as reduced fuel consumption can be expected by setting the temperature of the entire greenhouse low and locally heating the root zone and growing points of crops. For example, by locally maintaining the base of the plant (crown), where the growing points of strawberries are concentrated, at around 20°C during the coldest period, it becomes possible to set the nighttime temperature lower than when the greenhouse is not heated, which promotes increased yields and fruit growth, as well as significantly reducing heating costs.

[0025] On the other hand, regarding heating time, according to Non-Patent Document 3, when strawberry crown temperature is managed by heating the base (crown) of the plant for 12 hours during the day at 25°C, growth and yield are equivalent to conventional management of heating for 24 hours at 20°C, and the energy consumption related to crown heating is approximately 30% less when heated for 12 hours during the day at 25°C than when heated for 24 hours at 20°C.

[0026] From the above, it was found that localized heating of the crown promotes flower bud differentiation, increases yield, and contributes to energy conservation. Although there are some differences in the heating temperature, it is found that it is carried out within the range of approximately 20 to 25 degrees Celsius.

[0027] In the present invention, a high-intensity light source placed in contact with the base (crown) of a cultivated plant emits light, which generates heat, enabling localized heating of the base (crown).

[0028] Based on the above, a high-intensity light source that promotes photosynthesis should be used, and the surface temperature of the light source should be between 25°C and 28°C.

[0029] [Supplementary light] During the coldest months of the year, low levels of sunlight cause plants to insufficiently photosynthesize. As a result, photosynthetic products are insufficient, and the photosynthetic products required by flowers and fruits are not supplied, leading to an imbalance in growth and a tendency for poor growth. Specifically, the amount of stem elongation increases abnormally, resulting in what is known as spindly growth. Particularly in the case of cultivating seedlings, spindly seedlings will grow poorly after being planted in the field, resulting in plants with low productivity. In response to this, if supplemental lighting with a high-intensity light source can be used to obtain an amount of photosynthesis commensurate with the amount of photosynthetic products required for growth, growth will be stabilized.

[0030] Supplemental lighting using LEDs and other light sources is one of the most effective ways to increase the amount of photosynthesis in plants. In this case, it is particularly effective to provide supplemental lighting from the lower part of the canopy, where the light intensity is weaker, upward, rather than from the upper part of the canopy, which is already saturated with sunlight.

[0031] As is well known, when dealing with phenomena such as plant photosynthesis and photomorphogenesis, it is desirable to consider them in terms of photon numbers rather than energy amounts. When evaluating the light environment in a plant cultivation environment, the photosynthetically active photon flux density (hereinafter referred to as PPFD, unit: μmol m -2 ·s -1 ) is often used. For comparison, direct sunlight in midsummer has a PPFD of approximately 2000 μmol m -2 ·s -1 , and on cloudy days, it is about 50 to 100 μmol m -2 ·s -1 For horticultural crops grown in greenhouses, the light saturation point is approximately 500 to 1500 μmol m -2 ·s -1 It is said that (Non-Patent Document 4).

[0032] The light source used in this invention is a high-intensity light source with a high PPFD value for the purpose of promoting plant photosynthesis. It also has the function of heating the base (crown) of cultivated plants, so it is installed in contact with the base (crown) of the plant, with the light-emitting part facing upward so that it can irradiate the inside of the cultivated plant community, the lower part of the community, the underside of the leaves, etc.

[0033] [Heating, supplementary light time] In the present invention, due to the nature of heating using a heat source generated by the light source when it emits light, the heating time is the time the light source is on and emitting light. Supplementary light from a light source is intended to promote photosynthesis during the day, so irradiation is assumed to be approximately 12 hours during the day. On the other hand, as mentioned above, there is no difference in the yield increase effect between 24 hours of heating at 20°C and 12 hours of daytime heating at 25°C, so the heating and supplementary light times are the same. In other words, by irradiating a light source with a surface temperature of 25°C to 28°C for approximately 12 hours during the day, it is possible to simultaneously achieve both the effects of heating the base of the plant (crown) and supplementary light from a high-intensity light source.

[0034] As is well known, the process by which photosynthetic products (sugars) produced by photosynthesis in chloroplasts such as leaves of plants are transported to young leaves, flowers, and fruits is called translocation. For translocation to occur appropriately and for sugars to be distributed to flower buds and fruits, the plant must be actively photosynthesizing and storing photosynthetic products at the time of translocation. A high-intensity light source plays a role in promoting this photosynthesis. In other words, in this invention, the effects of crown heating during the coldest period include flower bud differentiation and fruit cluster enlargement. However, the photosynthetic products consumed to promote these activities are compensated for by the increased amount of photosynthesis achieved by supplemental lighting. This process is more efficient and effective than either of these measures alone, resulting in stable growth, accelerated growth, and greater yields.

[0035] [Example] The results of the method of the present invention at two strawberry cultivation sites are shown below. Example: Both were elevated strawberry cultivations, with seedlings planted in two rows per bench, as shown in Figure 1. A light source was attached to the base (crown) of each plant in a contacting manner. The light was on only during the day. (1) Strawberries: This was done in a facility without heating, and even without heating the greenhouse during the coldest periods, they were able to grow without any problems. Thanks to the effect of the light source, the seedlings grew without becoming leggy. (2) Strawberries: The facility is equipped with a heater, which is usually used multiple times during the coldest seasons. However, during this period, the number of times the heater was used was reduced, contributing to energy conservation. In addition, the fruit were observed to be enlarging. The method of the present invention was carried out at the two aforementioned locations with similar results.

[0036] Although the embodiments of the present invention have been described in detail above, the specific configuration is not limited to these embodiments, and the invention also includes changes in the method within the scope of the present invention without departing from the gist of the present invention. [Industrial Applicability]

[0037] The method of the present invention is suitable for plants such as fruit vegetables and flowers grown in facilities, and can be used not only in newly built facilities but also in existing cultivation facilities, and can be used for both elevated cultivation and soil cultivation. [Explanation of symbols]

[0038] 1. Cultivation bench 2 cultivation rows 3 Cultivated plants 4 Crown Department 5 light source

Claims

1. A method for promoting plant growth that uses a light source that is placed in contact with the base of crops grown in greenhouses during the coldest periods, enabling localized heating and supplemental lighting at the same time.

2. 2. A method for promoting plant growth according to claim 1, wherein a light source having a surface temperature of 25° C. or higher and 28° C. or lower when emitting light is used.

3. 3. The method for promoting plant growth according to claim 1 or 2, wherein a high-intensity light source is used.

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