JP2012228265A - Hydroponic method for plant - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydroponic method for plants by which autointoxication is hardly caused with more practicality than a conventional method.SOLUTION: The hydroponic method in a nearly closed system for the plants includes reducing the concentration of a growth inhibitor exuded from roots of the plants into a nutrient solution by electrolyzing the nutrient solution. The concentration of the growth inhibitor exuded from the roots of the plants into the nutrient solution may be reduced by electrolyzing the nutrient solution for the plants circulated in the nearly closed system. When the nutrient solution for the plants circulated in the nearly closed system is electrolyzed by providing the constitution, effects of the electrolysis, i.e. degrading effects on the inhibitor can be exercised on not only the vicinity of electrodes but also the whole culture solution and the electrolytic effects can uniformly be exercised.

Description

  The present invention relates to a hydroponic cultivation method in which self-poisoning of plants hardly occurs.

So far, in the hydroponic cultivation of strawberries, there have been many pouring methods that drain the culture solution out of the system, but in order to consider the environment and efficiently use water and fertilizer, the culture solution is not drained out of the system. We considered a so-called closed system.
However, in the case of closed-system hydroponics, unexplained yield reduction occurred in the latter half of the growth. In pursuit of the cause, when cultivating strawberry without changing the culture solution, the production inhibitory substance (allelopathy) exudes and accumulates in the culture solution from the roots, causing vegetative and reproductive growth. It was speculated that inhibition of self-intoxication would occur. That is, in closed-system hydroponics, the yield reduction in the latter half of the growth was thought to be caused by the growth-suppressing substances that exuded from the roots and accumulated in the culture solution.
Inhibition of vegetative growth and reproductive growth due to such self-poisoning is considered to be avoided by removing growth inhibitory substances accumulated in the culture solution. Proposed (see Patent Document 1).
However, when activated carbon is used as described above, there are practical problems with respect to its cost and recovery / treatment after use.
JP 2004-267140 A (paragraph 0035, etc.)

  Accordingly, the present invention is intended to provide a hydroponic cultivation method for plants that is less likely to cause self-poisoning and that is more practical than before.

In order to solve the above problems, the present invention takes the following technical means.
(1) The plant hydroponic cultivation method of the present invention is a substantially closed hydroponic cultivation method for a plant, wherein the concentration of the growth inhibitory substance exuded from the root of the plant into the nutrient solution is determined by electrolysis of the nutrient solution. It is characterized by reducing by doing.
In this nutrient solution cultivation method for plants, the concentration of the growth inhibitory substance exuded from the roots of the plant into the nutrient solution is reduced by electrolyzing the nutrient solution. The growth inhibiting substance can be reduced by an easy method. In addition, when hypochlorous acid is by-produced by electrolysis (generated when salt is present), it can control plant pathogens and increase the concentration of dissolved oxygen in the nutrient solution by electrolysis to increase fruit yield. Can be made.
Here, strawberries, tomatoes, cucumbers, eggplants, peppers, lettuce, spinach, komatsuna, honeybees, shungikus, saladna, mizuna, celery, leek, parsley (vegetables), eustoma, lilies, stocks, starches, carnations, roses , Aster, chrysanthemum, gerbera (flower) and the like. A benzoic acid can be illustrated as said growth inhibitory substance.
(2) The concentration of the growth inhibitory substance exuded from the root of the plant into the nutrient solution may be reduced by electrolyzing the nutrient solution of the plant circulated in a substantially closed system.
When constructed in this way and electrolyzed plant nutrient solution circulated in a substantially closed system, the electrolysis effect, that is, the decomposition effect of the inhibitory substance, can be applied not only to the vicinity of the electrode but also to the whole culture solution. The effect can be exerted uniformly. Moreover, it becomes easy to manage the culture solution at once, and stable cultivation can be performed on a large scale. Furthermore, when using a large aquarium that does not circulate, the fruit quality and yield of the strawberry, which is a cultivated plant, may become unstable due to variations in the composition of the culture solution and water temperature, which is negative for the producer. However, such a problem can be solved.
(3) You may make it provide the replenishment process of the nutrient solution component containing an iron chelating agent after the process of electrolyzing.
Instead of constantly electrolyzing during the cultivation period, it is electrolyzed at a predetermined time, and when configured as described above, the iron chelating agent in the nutrient solution component is prevented from being decomposed by electrolysis and the nutrient solution is Can be replenished. Examples of the iron chelating agent include Fe-EDTA (ethylenediaminetetraacetic acid).
(4) The electrolysis may be adjusted so that the production-suppressing substance has a predetermined low concentration. If comprised in this way, it can be anticipated that a plant will be stimulated by a low concentration production inhibitor to promote growth. The adjustment of this electrolysis can be controlled by the electrolysis intensity (current value, etc.) and frequency.
This hydroponic cultivation method for plants can be suitably applied to various uses such as hydroponics for strawberries, tomatoes, cucumbers, water quality maintenance devices for aquariums (underwater bonsai), and water quality maintenance devices for aquariums where cut flowers are placed. it can.

The present invention is configured as described above and has the following effects.
Since growth inhibitory substances can be reduced by a relatively easy method of electrolysis, it is possible to provide a hydroponic cultivation method for plants that is less likely to cause self-poisoning and that is more practical than before.

Embodiments of the present invention will be described below.
The hydroponic cultivation method of the plant of this embodiment is a substantially closed system hydroponic cultivation method (hydroponic cultivation) of strawberries, and by electrolyzing the nutrient solution of the plant (strawberry) to be circulated in a substantially closed system, The concentration of a growth inhibitory substance (focusing on benzoic acid) that exudes from the roots of the plant into the nutrient solution was reduced.
In addition, a replenishment step of a nutrient solution component containing an iron chelating agent was provided after the electrolysis step, so that the nutrient solution was replenished at regular intervals during the strawberry growth period. Examples of the iron chelating agent include Fe-EDTA (ethylenediaminetetraacetic acid).

Next, the usage state of the plant hydroponics method of this embodiment is demonstrated.
In this method of hydroponic cultivation of plants (strawberry), the concentration of a growth inhibitory substance (benzoic acid) that exudes from the root of the plant into the nutrient solution by electrolyzing the nutrient solution of the plant that is circulated in a substantially closed system. Therefore, there is an advantage that the growth inhibitory substance can be reduced by a relatively easy method such as electrolysis, and self-poisoning hardly occurs and is more practical than before.
In addition, when hypochlorous acid is by-produced by electrolysis (generated when salt is present), it can control plant pathogens and increase the concentration of dissolved oxygen in the nutrient solution by electrolysis to increase fruit yield. There is an advantage that can be made.
In addition, it is not always electrolyzed during the cultivation period, but is electrolyzed at a predetermined time, and after the electrolyzing step, a replenishment step of a nutrient solution component containing an iron chelating agent is provided. By this, it is possible to prevent the iron chelating agent in the nutrient solution component from being decomposed and replenish the nutrient solution.
By the way, not all of the production-suppressing substances (benzoic acid and the like) are decomposed, but electrolysis may be adjusted so as to obtain a predetermined low concentration. The adjustment of this electrolysis can be controlled by the electrolysis intensity (current value, etc.) and frequency. If it does in this way, it can be anticipated that a plant will be stimulated by a low concentration production inhibitor to promote growth.

[Experiment 1]
Decomposition of benzoic acid added to the culture by electrolysis.
1 L of the culture was placed in a glass beaker for experiments. The culture solution was diluted and adjusted to EC 0.8dS m ^-1 (hereinafter referred to as the reference solution) according to the standard solution 12). The treatment group is a group in which only the reference solution is placed in a glass beaker (control group), a group in which 400 μM benzoic acid is added to the reference solution (benzoic acid addition group), and an electrolysis treatment is performed in the benzoic acid addition group (electricity treatment) Decomposition zone) was set up for a total of 3 treatment zones.
As shown in FIG. 1, in the electrolysis section, an electrode using titanium having a surface area of about 180 cm ^{2 for} the cathode 1 and 42 cm ^{2 for} the anode 2 is placed in a glass beaker (not shown) and energized for 24 hours. Was performed. The voltage and current during energization were 10.0 V and 0.6 A, respectively. During the experiment, the room temperature was 18 ° C, the glass beaker was kept in a water bath, and the internal liquid temperature was maintained at 20 ° C. At the start of the experiment, the glass beaker was agitated and the culture was sampled 2, 6, 12 and 24 hours later. Analytical high performance liquid chromatography (HPLC. Column oven: L-2350, detector: L-2400, pump: L-2130; Hitachi, Ltd. and data processing equipment: 25 μl of the culture solution filtered through a syringe filter (0.45μ) Chromatopack C-R8A (Shimadzu Corporation) was measured and benzoic acid in the culture was measured. The analysis conditions were as follows: solvent 10 mM phosphoric acid-acetonitrile mixture (70%: 30%), flow rate 1.0 ml min-1, analysis temperature 30 ° C., detection wavelength 254 nm, column 4.0 × 200 mm (Wakosil 10C18, Wako Pure Chemical Industries) did.
Here, when electrolysis is performed in an aqueous solution containing ethylenediaminetetraacetic acid (EDTA), EDTA is decomposed and Fe-EDTA added as an iron source in the garden trial formulation can be decomposed by electrolysis Sex was considered. Therefore, the concentration transition of Fe-EDTA was measured under the same analytical conditions.
As shown in FIG. 2 (graph of the transition of the concentration of benzoic acid added to the culture solution), the benzoic acid concentration in the benzoic acid-added section was 380 after 2 hours, 352 after 6 hours, 347 after 12 hours and 347 μm after 24 hours. After 24 hours, the remaining amount of benzoic acid in the culture was 81% at the start of the experiment. On the other hand, in the electrolysis section, it changed to 259 after 2 hours, 223 after 6 hours, 185 after 12 hours, and 67 μM after 24 hours, and the residual amount of benzoic acid in the culture medium after 24 hours was 17% at the start of the experiment. there were. In this experiment, benzoic acid, a phenolic acid, was considered to have been decomposed by the electrolysis treatment because the benzoic acid added was greatly reduced by the electrolysis treatment in the culture medium. In addition, benzoic acid in the culture broth decreased to 81% even in the benzoic acid-added section where electrolysis was not performed. It is considered that phenolic acid is decomposed by microorganisms present in the culture solution. In this experiment, it was assumed that the added benzoic acid was decomposed by microorganisms due to the microorganisms present in the culture solution.
As shown in Fig. 3 (graph of the effect of electrolysis treatment on the concentration of Fe-EDTA in the culture solution), the concentration of Fe-EDTA in the culture solution, which was 25 mgL ^-1 at the start of the experiment, was 24 hours later. In the benzoic acid group, it was 18.3 mgL- ¹ . On the other hand, it was 2.3 mgL ^-1 in the electrolysis section. The decrease of Fe-EDTA in the electrolysis zone was considered to be due to the decomposition by electrolysis. Fe-EDTA was also reduced in the benzoic acid-added section where electrolysis was not performed. Since Fe-EDTA in the culture solution is usually supposed to be decomposed by light, particularly ultraviolet rays, it is possible that Fe-EDTA in the culture solution was decomposed by ultraviolet rays derived from outdoor or fluorescent lamps. It was.
These results suggest that benzoic acid, which is the main causative substance in self-poisoning of strawberries, is decomposed by electrolysis, which may lead to avoidance of growth inhibition. However, benzoic acid is not the only exudate from roots that indicates self-poisoning of strawberries. Next, we investigated whether the growth inhibitory substances can be decomposed by electrolysis using the culture residue used in the hydroponics of strawberry.

[Experiment 2]
Effects of benzoic acid added to the culture solution and electrolysis of the culture residue on the growth of strawberry seedlings.
The test varieties used were 'Toyonoka (strawberry variety)'. The seedlings in the four leaf development stage were supported by urethane cubes and planted in a plastic container (17cm x 29cm x 9.5cm) containing 3L of the culture solution. The number of trees planted was 10 per container. The treatment group is a group using a reference solution (new solution group, control group), a group where benzoic acid at a concentration of 400 μM is added to the new solution (benzoic acid added group), and about 8 months for hydroponics of strawberry 'Toyonoka' Use the culture residue used during the period (residual liquid group), and in the benzoic acid-added group and the residual liquid group, there are sections to be electrolyzed (benzoic acid electrolytic zone and residual liquid electrolytic zone, respectively) for a total of 5 treatments It was warded. In the benzoic acid electrolysis section and the residual liquid electrolysis section, each culture solution was electrolyzed before starting the experiment. The electrolysis was performed for 24 hours according to Experiment 1. In all treatment sections, the entire culture was changed every 4-5 days. At that time, the same culture solution was used in each treatment section as at the start of the experiment. In the benzoic acid electrolysis zone, the residual liquor zone, and the residual liquor electrolysis zone, the NO ₃ ⁻ , PO ₄ ³⁻ , K ⁺ , Ca ²⁺ , Mg ²⁺ and Mg ²⁺ Adjustment was made so that each ion concentration of Fe ³⁺ was almost the same as the reference solution. At this time, NO ₃ ^- colorimeter for ions _{(RQflex2, Merck), PO 4} 3- ions molybdenum blue method 14 for), K ^+, Ca ^2+, for each ion concentration of Mg ²⁺ and Fe ³⁺ Were analyzed using an atomic absorption photometer (Z-5010, Hitachi, Ltd.). In addition, the pH and EC of the culture solution were measured with a pH meter (F-52, Horiba Seisakusho) and EC meter (ES-12, Horiba Seisakusho), and the standard solution (pH = 7.0, EC = 0.8 dS m ⁻¹⁾ . It was adjusted to be the same as the actual measured value. At that time, 0.4M NaOH was used for pH, and tap water was used for EC.
Using a culture apparatus equipped with a fluorescent lamp, the cells were cultured for 2 weeks under conditions of room temperature of 25 ° C, photon flux density of 74-81μmolm-2s-1, and 16 hours of day length. At the end of the experiment, the number of leaves, maximum leaf length, maximum leaf width, above-ground weight and maximum root length were measured.
As shown in Table 1, there was no significant difference in the number of leaves at the end of the experiment depending on the treatment group. Next, the body weight of the ground part decreased significantly in the benzoic acid-added group to 55% of the control group. In the residual liquid group, it was 61% of the control group, and it was significantly decreased as in the benzoic acid-added group. There was no significant difference between the benzoic acid electrolysis section and the residual liquid electrolysis section. The maximum leaf length and maximum leaf width were significantly decreased in the benzoic acid-added group, 78% and 72%, respectively, in the control group. Also in the residual liquid group, it decreased significantly to 77% and 69% of the control group, respectively. On the other hand, there was no significant difference in the benzoic acid electrolysis section and the residual liquid electrolysis section compared with the control section. There was no significant difference in the treatment interval for the maximum root length.

When strawberry seedlings were cultivated using a culture solution to which benzoic acid was added, the growth of seedlings was suppressed, and it was considered that the above-ground growth suppression in the benzoic acid-added section was caused by benzoic acid. It was. On the other hand, experiment 1 suggested that benzoic acid was decomposed by electrolysis, so the suppression of above-ground growth in the benzoic acid electrolysis zone was because benzoic acid in the culture broth was decomposed by electrolysis. it was thought.
In hydroponic tomatoes and cucumbers, growth-inhibiting substances leached from the roots accumulate in the culture. Therefore, the decrease in growth in this experiment was thought to be due to growth inhibitory substances accumulated in the culture medium. The main causative agent of vegetative and reproductive growth inhibition in strawberry culture medium exchange is the presence of benzoic acid that exudes from the roots and accumulates in the culture medium. Therefore, in this experiment, benzoic acid was considered to be the main growth inhibitor in the culture residue. In addition, experiment 1 suggested that benzoic acid in the culture broth was decomposed by electrolysis treatment. Therefore, the reduction of growth inhibition in the residual liquid electrolytic zone is thought to be due to the decomposition of growth inhibitory substances such as benzoic acid by electrolysis. It was.
These results suggested that the growth inhibitory substances thought to have accumulated in the culture residue were decomposed by electrolysis and the growth inhibition was avoided. Next, we investigated the effects of electrolysis of the broth on the reproductive growth, that is, flowering and yield of strawberries.

[Experiment 3]
Effects of medium exchange and electrolysis on growth and yield of strawberries.
The test varieties used were 'Toyonoka'. The experiment was conducted in a glass greenhouse in the Bioresource Education Research Center attached to the Faculty of Bioresource Sciences, Shimane University (Kamihonjo Town, Matsue City, Shimane Prefecture). The experiment was conducted by hydroponics. The culture solution was used as a reference solution. As shown in FIG. 4 (culture apparatus using Wagner pot), a 1.0 × 5000-1a Wagner pot processed to a volume of 3 L, a culture tank with a capacity of about 50 L, a submersible pump 5 ( KP-101, Kojin), a cultivation device consisting of an irrigation tube with an inner diameter of φ4 mm 6, a vinyl chloride feed pipe 7 with an inner diameter of φ15 mm, and a drain pipe 8 was used. Three to four true leaves and a seedling with a crown diameter of about 10 mm were supported by four urethane cubes (length 23 mm x width 23 mm x height 27 mm) and transplanted to a cultivation device. The culture medium was circulated for 5 minutes and rested for 30 minutes using a program timer (KS-1500, Seiei Iuchi), and the supply volume was ¹ Lmin- ¹ .
The treatment group is a group in which the culture medium is exchanged every two weeks (hereinafter referred to as an exchange group) and a group in which the culture medium is not exchanged (hereinafter referred to as a non-exchange area). After the start period, a zone (hereinafter referred to as electrolysis zone) in which electrolysis treatment was performed in the culture solution every 2 weeks was established for a total of 3 treatment zones. The electrolysis process in the electrolytic zone was performed in the culture tank. The electrodes and energization time were in accordance with Experiment 1, and the voltage and current during energization were 18.0 V and 0.2 A, respectively.
In a non-exchange group and the electrolyte-ku, NO ₃ with adding a reduced culture every two weeks _{^{-, PO 4 3-, K +}} , Ca 2+, analyzes each ion concentration of Mg ²⁺ and Fe ³⁺ The concentration was adjusted to the same as that of the reference solution. Since it was considered that Fe-EDTA in the culture broth was decomposed by electrolysis, these adjustments were made after the electrolysis. The method for adjusting inorganic nutrients was the same as Experiment 2.
The number of planted plants was one per pot and 10 iterations were performed. During the experiment, the daily average temperature was 13.1 to 28.1 ° C, and the daily average water temperature was 5.6 to 25.4 ° C. In both treatments, the pH and EC of the cultures were 5.8 to 7.6 and 0.7 to 1.2 dS m ^-1 , respectively. Pollination was performed using a paint brush. The fruit was harvested when the whole fruit was colored, and the experiment was terminated about 6 months after the fruit was harvested. At that time, the number of leaves per strain, crown diameter, ground weight and dry weight, underground dry weight and maximum root length were investigated. In addition, the number of florets, the number of blooms, the number of fruits harvested, and the yield were recorded during the experiment.

  As shown in Table 2, the number of leaves at the end of the experiment decreased significantly in the non-exchange zone and the electrolysis zone, reaching 59% and 60% of the control zone, respectively. There was no significant difference in crown diameter between treatment groups. The above-ground living weight, dry weight, and underground dry weight were significantly smaller in the non-exchange zone and electrolytic zone than in the control zone, but tended to be slightly higher in the electrolytic zone. There was no significant difference in the maximum root length in each treatment interval. When strawberry cultivation is performed without changing the culture solution, vegetative growth is suppressed by growth inhibitory substances that exude from the roots. Therefore, the growth inhibition in the non-exchange zone in this experiment was considered to be due to the growth inhibitory substance that exuded from the roots and was present in the culture solution. In Experiment 2, it was suggested that the growth inhibitory substance was decomposed by electrolysis in the culture residue, but in this experiment, the number of leaves, the weight of above-ground biological weight and the weight of underground dry matter were also measured in the electrolytic zone. Was significantly reduced compared with the control group. Therefore, it was considered that growth inhibition due to non-exchange of culture medium was not avoided by electrolysis. In this experiment, the electrolysis treatment was performed after the beginning of the 3rd inflorescence harvest. This suggests that the suppression of vegetative growth by growth-suppressing substances exuded from the root may have occurred at least before the start of the third inflorescence harvest. In this experiment, the mineral nutrients in the culture broth were adjusted after the electrolysis treatment, so the difference in Fe-EDTA was not considered to be in the treatment section.

Next, as shown in Table 3, there was no significant difference between the treatment intervals in terms of reproductive growth and the number of inflorescences. The number of flowering decreased significantly in the non-exchange zone, which was 73% of the control zone. There was no significant difference in the electrolysis group compared to the control group. The number of harvested fruits decreased significantly in the non-exchange zone, 56% of the control zone, but there was no significant difference in the electrolysis zone. The yield was significantly decreased in both the non-exchange zone and the electrolysis zone compared to the control zone, 47% and 71% of the control zone, respectively.

When strawberry cultivation is carried out without changing the culture solution, growth inhibition and reproductive growth are suppressed by the growth inhibitory substance exuded from the root, and the main causative substance may be benzoic acid. Moreover, it is possible that auxin, which is said to control the development of reproductive growth in plants and the fruit enlargement in strawberry, is inhibited by benzoic acid absorbed from the roots. Therefore, it was considered that the suppression of reproductive growth in the non-exchange zone in this experiment was caused by absorption of benzoic acid accumulated in the culture medium from the roots.
On the other hand, the number of flowers and the number of fruits harvested in the electrolysis plot were the same as those in the control plot. The yield decreased significantly compared to the control group, but increased significantly compared to the non-exchanged group, suggesting that the decrease in yield due to non-exchanged medium was alleviated. Experiments 1 and 2 suggested that benzoic acid in the culture broth was decomposed by electrolysis. Therefore, the number of flowers in the electrolytic zone, the recovery of the number of harvested fruits, and the reduction in yield loss were exuded from the roots of strawberries. This was probably due to the electrolysis of benzoic acid, which was thought to have accumulated in the culture medium.
These results suggest that the decrease in yield due to growth inhibitory substances that exude from strawberry roots and accumulate in the culture, that is, autotoxicity, may be reduced by electrolyzing the culture. In addition, since Fe-EDTA in the culture solution was considered to have been decomposed by electrolysis treatment, in the future, when performing electrolysis treatment in strawberry hydroponics, the treatment should be performed immediately before the adjustment of the culture solution. It was considered necessary to examine the timing of processing.

  The growth inhibitory substance can be reduced by a relatively easy method of electrolysis, and self-poisoning is less likely to occur and is more practical than before, so that it can be applied to the hydroponic use of various plants. it can.

The schematic perspective view of the electrode explaining embodiment of the nutrient solution cultivation method of the plant of this invention. The graph of transition of the benzoic acid concentration added to the culture solution. The graph of the influence which electrolysis processing has on the density | concentration of Fe-EDTA in a culture solution. Explanatory drawing of the culture apparatus using the Wagner pot explaining embodiment of the nutrient solution cultivation method of the plant of this invention.

1 cathode 2 anode

Claims (3)

A substantially closed hydroponic cultivation method for a plant, characterized in that the concentration of a growth inhibitory substance exuded from the root of the plant into the nutrient solution is reduced by electrolyzing the nutrient solution. Hydroponic cultivation method for plants. The hydroponic cultivation of the plant according to claim 1, wherein the concentration of the growth inhibitory substance exuded from the root of the plant into the nutrient solution is reduced by electrolyzing the nutrient solution of the plant circulated in a substantially closed system. Method. The method for hydroponic cultivation of plants according to claim 1 or 2, wherein the electrolysis is adjusted so that the production inhibitory substance has a predetermined low concentration.