JP2018033368A - Hydroponic method and hydroponic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide hydroponic methods and hydroponic devices which can sufficiently raise agricultural products while reducing the amount of the nitrate comprised in agricultural products.SOLUTION: The present invention relates to a method for cultivating agricultural products with nutrient solution in a light and dark cycle including the light period in which agricultural products are irradiated with a light and the dark period in which agricultural products are not irradiated with a light or irradiated with a light less than that in the light period, in 24 hours. The hydroponic method of the invention comprises a first cultivation step of contacting the root of an agricultural product with a first liquid containing nitrate ion, a second cultivation step of contacting the root of the agricultural product with a second solution substantially containing no nitrate ion. Then, in the light period, a first cultivation step is performed for 10% or more of the light period, and in the dark period, a second cultivation step is performed for 50% or more of the dark period.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a hydroponic cultivation method and a hydroponic cultivation apparatus.

  Nitrogen sources (nitrogen compounds such as nitrates and ammonium salts) are necessary for growing crops. Inorganic nitrogen in soil includes ammonia nitrogen, nitrite nitrogen, nitrate nitrogen, and urea nitrogen, but it has been found that crops grow well when they mainly absorb nitrate nitrogen. For this reason, in hydroponic cultivation, a large amount of nitrate nitrogen is contained as a nitrogen source in the culture solution.

  Therefore, the amount of nitrate accumulated in the crop is apt to increase in the hydroponically grown crop compared to soil cultivation. However, nitrate causes an increase in savory components such as oxalic acid. Nitrate also becomes nitrite in the body, which can cause methemoglobinemia. Furthermore, when nitrite reacts with amines, nitrosamine with high carcinogenicity is produced. For these reasons, it is desirable that the amount of nitrate contained in the crop is as small as possible.

  Patent Document 1 (Japanese Patent Laid-Open No. 6-105625) discloses a hydroponic fertilizer solution that does not contain nitrate nitrogen for two to several days in a certain period before harvesting in hydroponics (nutriculture) of vegetables. A method of reducing the amount of nitrate contained in vegetables by using (culture medium) is disclosed.

JP-A-6-105625

  However, in the hydroponics, there is a problem that the amount of crops grown is greatly reduced when a culture solution containing no nitrate nitrogen is used for a certain period.

  The present invention has been made in view of the above problems, and provides a hydroponic cultivation method and a hydroponic cultivation apparatus that can sufficiently grow a crop while reducing the amount of nitrate contained in the crop. The purpose is to do.

  The present invention includes a light period in which light is applied to a crop within 24 hours, and a dark period in which light is not applied to the crop, or the light is applied to the crop with less light than the light period. This is a hydroponics method for hydroponically cultivating agricultural crops under a light / dark cycle. In the hydroponic cultivation method of the present invention, the first cultivation step in which the root of the crop is brought into contact with a first liquid containing nitrate ions, and the root of the crop is brought into contact with a second liquid that is substantially free of nitrate ions. A second cultivation step. In the light period, the first cultivation process is performed for 10% or more of the light period, and in the dark period, the second cultivation process is performed for 50% or more of the dark period.

  It is preferable that the washing | cleaning process of wash | cleaning the root area of agricultural products is further included between the said 1st cultivation process and the said 2nd cultivation process.

  It is preferable that the first liquid further includes nutrients other than the nitrate ions. The crop is preferably a vegetable. The vegetable is preferably a leaf vegetable.

  The present invention is also a hydroponic cultivation apparatus used in the above-described hydroponic cultivation method, wherein the first liquid supply apparatus for supplying the first liquid around the root of the agricultural crop, And a second liquid supply device for supplying the second liquid around the roots.

  It is preferable that the said hydroponic cultivation apparatus contains the washing | cleaning apparatus for wash | cleaning the root area of the said crop.

  ADVANTAGE OF THE INVENTION According to this invention, the nutrient solution cultivation method and nutrient solution cultivation apparatus which can fully grow a crop can be provided, reducing the quantity of the nitrate contained in a crop.

It is a schematic diagram which shows an example of the hydroponic cultivation apparatus of this invention. It is a flowchart for demonstrating an example of the hydroponic cultivation method of this invention. It is a graph which shows the measurement result of the test example 1 about lettuce (variety: green wave). It is a graph which shows the measurement result of the test example 1 about lettuce (variety: crunch). It is a graph which shows the relationship between nitrate ion content and glucose content about the measurement result of the test example 1 about lettuce (variety: green wave). It is a graph which shows the relationship between a nitrate ion content and a glucose content about the measurement result of the test example 1 about lettuce (variety: crunch).

  Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited thereto. In the drawings, the same reference numerals represent the same or corresponding parts.

  The nutrient solution cultivation method of the present invention is a cultivation method for cultivating agricultural crops using a solution (culture solution) obtained by dissolving fertilizer (nutrient) in water without using soil. The advantages of hydroponics include the ability to avoid soil diseases and continuous cropping failures, the omission of work necessary for soil cultivation such as plowing, anchoring, soil laying, fertilization and weeding, and automation of liquid supply and fertilization management. There are some things, such as improving the use efficiency of fertilizer and water.

  The culture solution is a solution obtained by dissolving nutrients (essential elements) necessary for plant growth in water at a concentration suitable for absorption. Various types of culture solutions can be used according to the type of crop to be cultivated and the quality of the target crop.

  Nutrients contained in the culture solution basically exist in an ionic state, and this is absorbed by the crops. Examples of nutrients include nitrogen, phosphorus, potassium, calcium, magnesium and sulfur, which are nutrients (elements) required in relatively large amounts. Among these, nitrogen is mainly contained as nitrate ions (nitrate nitrogen) in the culture solution. Further, examples of nutrients (trace elements) that may be contained in a trace amount include chlorine, boron, iron, manganese, zinc, copper, and molybdenum.

  In the present embodiment, the “agricultural crops” are, for example, vegetables, fruits, cereals, beans, tea, flowers, etc., preferably vegetables. The vegetable is preferably a leaf vegetable.

  Leafy vegetables are vegetables that mainly use the leaf portion as an edible material, and are also called leafy vegetables, leafy products, and the like. Among the vegetables cultivated by the conventional hydroponics method, there was a tendency that the content of nitrate in the edible part increased especially for leaf vegetables.

  In addition, the nutrient solution cultivation method disclosed in Patent Document 1 specifically discloses only an application example for spinach (non-headed leaf vegetables). And by examination of the present inventors, when the hydroponic cultivation method disclosed in Patent Document 1 is applied to lettuce (non-ballistic), the content of nitrate can be reduced, but growth is significantly suppressed. It has been confirmed.

  In the hydroponic cultivation method of the present invention, a crop is hydroponically cultivated under a light / dark cycle including a light period and a dark period within 24 hours.

The light period is a period (hour) during which light is applied to the crop. The intensity of light applied to the crops in the light period is preferably 5 μmol / m ² / sec or more, more preferably 50 to 2000 μmol / m ² / sec, and even more preferably 100 to 200 μmol / m ² / sec. It is.

  In the light period, it is known that the activity of nitrate reductase contained in agricultural crops increases due to some influence caused by such light irradiation. For this reason, even if agricultural products absorb nitrate nitrogen, nitrate ions are reduced and accumulation of nitrate ions is considered to be suppressed. The nitrite ions generated by the reduction of nitrate ions are further reduced by nitrite reductase to finally become ammonium ions. The rate-limiting step of the nitrate reduction reaction from nitrate ions to ammonium ions is the nitrate ion. It is a reduction reaction from nitrite ions.

  In addition, the light irradiated from the light source 6 (refer FIG. 1) may be sufficient, and sunlight may be sufficient as light. As the light source, for example, a fluorescent lamp, an HID (High Intensity Discharge) lamp, an LED (light emitting diode), or the like can be suitably used.

  On the other hand, the dark period is a period in which the crop is not irradiated with light or the crop is irradiated with light having a light amount smaller than that in the light period. In the dark period, nitrate reductase activity is low, so it is considered that nitrates are likely to accumulate when crops absorb nitrate nitrogen.

  Both the light period and the dark period are preferably 3 hours or more, more preferably 6 hours or more, and further preferably 9 hours or more.

  The light-dark cycle may be a repetition of one type of 24-hour cycle consisting of a specific light period and dark period, or a combination of a plurality of types of 24-hour cycles consisting of a specific light period and dark period. The light period and dark period included in the 24-hour cycle are usually once each, but may be included multiple times.

  FIG. 1 is a schematic view showing an example of the hydroponic cultivation apparatus of the present invention. Moreover, FIG. 2 is a flowchart for demonstrating an example of the hydroponics method of this invention. Hereinafter, with reference to FIG. 1 and FIG. 2, an example of the nourishing culture method and the nourishing culture apparatus of this embodiment is demonstrated.

  The cultivation method of this embodiment includes a first cultivation process (S10), a washing process (S30), and a second cultivation process (S50).

[First cultivation step (S10)]
In a 1st cultivation process (S10), the root of agricultural products is made to contact the 1st liquid containing nitrate ion.

  Specifically, referring to FIG. 1, the valves 21, 31 are opened (the valves 22, 23, 32, 33 are closed), and the first pump 41 is driven to store the first liquid. The first liquid in the tank 51 is supplied to one end of the cultivation bed 1 for hydroponics via the valve 21.

  In the cultivation bed 1, for example, a support for supporting the roots of crops or the like in a tray such as a tray having a lower slope from the valve 23 side toward the opposite end or a horizontal tray is provided. It is installed at a distance from the bottom of the tray. Examples of the support include a resin plate having a plurality of holes for planting and a urethane mat.

  With such a configuration, the first liquid passes through the entire cultivation bed 1 so as to come into contact with the roots of the crops, and returns to the first tank 51 through the valve 31.

  And the 1st cultivation process (S10) is carried out for 10% or more of the above-mentioned light period, preferably 20% or more, more preferably 30% or more, and still more preferably 50% or more. The first cultivation process may be performed for 100% of the light period. In this way, in the light period, nitrate ions (nitrate nitrogen) are absorbed by the crops, nitrate is reduced by the activation of nitrate reductase, the accumulation of nitrate is suppressed, and the crops absorb nitrate nitrogen. By absorbing it, the growth of crops is maintained within an acceptable range.

  After the 1st cultivation process (S10), the 1st pump 41 (1st liquid supply device) for supplying the 1st liquid is stopped (S20), and it moves to the following washing process (S30).

[Washing step (S30)]
In the washing step (S30), the root area of the crop (around the root and the root including the cultivation bed 1) is washed.

  Specifically, the valves 23 and 33 are opened (the valves 21, 22, 31, and 32 are closed), and water such as dechlorinated water is supplied to the one end of the cultivation bed 1 for hydroponics via the valve 23. To supply. As a result, the water passes through the entire cultivation bed 1 while washing the root area (root and cultivation bed 1) of the crop and is drained through the valve 33.

  By carrying out the washing step (S30) in this way, since nitrate ions do not remain in the root area of the crop in the next second cultivation step (S50), no nitric acid is contained in the second cultivation step (S50). The effect of circulating the second liquid can be effectively exhibited.

  The washing step (S30) is not an essential step, but if the second step is circulated in the next second cultivation step (S50) unless the washing step (S30) is carried out, the second liquor is in the first liquor. Therefore, there is a possibility that the desired effect cannot be obtained.

[Second cultivation step (S50)]
In a 2nd cultivation process (S50), it is made to contact with the 2nd liquid which does not contain nitrate ion substantially.

  Specifically, the valves 22 and 32 are opened (the valves 21, 23, 31, and 33 are closed), and the second pump 42 is driven to store the second liquid in the second tank 52 that stores the second liquid. Is supplied to one end of the cultivation bed 1 for hydroponics via a valve 22. Thereby, like the 1st cultivation process, the 2nd liquid passes the whole cultivation bed 1 so that it may contact with the root of agricultural products, and returns to the 2nd tank 52 via valve 32.

  And a 2nd cultivation process (S50) is implemented 50% or more of the said dark period, Preferably it is 70% or more, More preferably, it is 90% or more of time. The second cultivation process may be performed for 100% of the light period. Thus, nitrate accumulation is suppressed by preventing nitrate ions (nitrate nitrogen) from being absorbed by crops in the dark period when nitrate reductase is not activated and nitric acid is difficult to be reduced.

  After the 2nd cultivation process (S50), the 2nd pump 42 (2nd liquid supply device) for supplying the 2nd liquid is stopped (S60), and when continuing cultivation, the 1st washing process (S10) Return to.

  In addition, in said embodiment, although the supply system of a culture solution is the circulation type which circulates a culture solution between a cultivation bed and a tank, a non-circulation type may be sufficient. From the viewpoint of improving the utilization efficiency of nutrients and environmental conservation, it is preferable that the culture solution supply system is a circulation type.

  As the non-circulating type, there is a pouring type in which surplus culture solution that has not been absorbed by the crop is discarded as it is, and is often used in solid medium cultivation or the like. In the case of the flow-through type, the above-described cleaning step (S30) may not be particularly performed. This is because nitrate ions in the first liquid are eliminated if a predetermined amount of the second liquid flows on the cultivation bed.

  According to the nourishing liquid cultivation method of this embodiment mentioned above, it grows with the 1st liquid which contains nitric acid in the light period when nitrate reduction activity is high, and it is 2nd liquid which does not contain nitric acid in the dark period when nitrate reduction activity falls. By performing cultivation, the crop can be sufficiently grown while reducing the amount of nitrate contained in the crop.

  In addition, according to the hydroponic cultivation method of the present embodiment, it is possible to increase the content of sugar (such as glucose, fructose, sucrose) in agricultural products.

  Heretofore, a method for dividing one day into a light period and a dark period and adjusting the dosage of nitrate nitrogen within the day according to the light period and the dark period has not been known.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

Example 1
In Example 1, the hydroponics which is an example of the said embodiment was performed about 2 types of bulbous leaf vegetables (lettuce). As the lettuce, two varieties of “green wave” (Takii Seed and Seed Co., Ltd.) that is leaf lettuce and “crunch” (Turuta Seed Co., Ltd.) that is a frilled lettuce were used.

(1) Hydroponic cultivation apparatus A closed-type artificial meteorograph (LPH-220SP-S, Nippon Medical Instrument Co., Ltd.) was used as a cultivation room. In addition, a CO ₂ control device (SF6200, Science Sakai Electronics Co., Ltd.) was installed in the artificial weather device. Therefore, it is possible to control the growth temperature, the day length (the length of the light period), and the CO ₂ concentration in the artificial weather device.

  There are two upper and lower cultivation shelves in the artificial meteorological chamber, and two submerged hydroponic devices (cultivation beds) were placed in each. As the cultivation bed, an apparatus was used in which a plastic plate (vertical 28 cm × horizontal 17 cm) was provided on the upper surface of a horizontally disposed plastic tray having a width of 16 cm × depth of 25.5 cm × height of 15 cm. The plastic plate is provided with four holes (for planting) having a diameter of 1.5 cm and holes for ventilation. Each cultivation bed was ventilated using an air pump.

As a light source, using a three-wavelength type daylight white fluorescent lamp, the average photosynthetic photon flux density of cultivation surface (PPFD) is the upper 300 [mu] mol / ^{m 2} / sec, it was lower 250μmol / ^{m 2} / sec.

(2) Hydroponic cultivation method Using the above-mentioned hydroponic cultivation apparatus (artificial meteorological device and cultivation bed), the growth temperature in the artificial meteorological device is 23 ° C, and the CO ₂ concentration is controlled to 700 ppm, Fluorescent lamp lighting time (light period) is set to 12 hours (9: 00 to 21:00), lettuce seedling and planting of lettuce (variety: crunch (lower) and green wave (upper)) It was.

  That is, 50 seeds of each kind of lettuce were sown in a hydroponic urethane mat soaked in an artificial meteorograph. The culture solution was applied after germination (3-4 days after sowing). One week after sowing, the seedling was transplanted to a submerged hydroponic device and raised for another week.

As the culture solution, a basic culture solution with 1/2 unit of garden trial formulation was used. The composition of the large amount element in the culture solution is as shown in Table 1 and contains nitrate nitrogen (nitrate ion: NO ₃ ⁻ ). In addition, OAT house fertilizer No. 5 was added to the culture solution at a rate of 0.05 g / L as a trace element.

  After raising the seedlings for 2 weeks in this way, lettuce of each varieties was planted 4 by 3 in 3 cultivation beds (a total of 16 in each artificial weather instrument).

  One week after planting, the plant is cultivated in a cultivation bed (hydroponic device) filled with the same culture solution in the light period (9:00 to 21:00) and dark (21:00 to the next 9 The culture solution was exchanged with water every day so that it could be cultivated in a cultivation bed filled with water (dechlorinated water) at 0:00) and cultivated for 2 weeks. When exchanging the culture solution and water, the root area was washed away with washing water, and the cultivation was resumed after draining water well. That is, except for the time required for the washing process, the first cultivation process was carried out for almost 100% of the light period (12 hours), and the second cultivation process was carried out for almost 100% of the dark period (12 hours). . In these two weeks, the culture medium was replaced with a new one when one week passed. After two weeks of cultivation, leaf lettuce was harvested.

(Comparative Example 1)
In Comparative Example 1, in the cultivation for 2 weeks after the planting, the cultivation was continued using only the same culture solution as in Example 1. Except for that point, two types of lettuce were cultivated in the same manner as in Example 1.

(Comparative Example 2)
In Comparative Example 2, in the cultivation for 2 weeks after planting, it was cultivated in a cultivation bed filled with water (dechlorinated water) in the light period (9: 00 to 21:00), and the dark period (21: 00 to the next) At 9:00), the culture solution and water were exchanged every day so that the cultivation bed filled with the same culture solution as in Example 1 could be cultivated. Except for that point, two types of lettuce were cultivated in the same manner as in Example 1.

[Test Example 1]
About lettuce ("green wave" and "crunch") harvested in Example 1, Comparative Example 1 and Comparative Example 2 above, immediately after harvesting, the above-ground living weight, leaf nitrate ion content and leaf glucose content Was measured.

(1) Measurement of above-ground living weight The harvested leaf lettuce was divided into the above-ground portion and the root, and the above-ground living weight was measured.

  The measurement results (average value: n = 3) of the above-ground living body weight are shown in FIG. 3A for green waves and in FIG. 4A for crunches.

(2) Measurement of nitrate ion content in leaf Four times the amount of water was added to about half of the harvested leaf lettuce, ground with a mixer, wrapped in gauze and squeezed to obtain a juice. The obtained juice was diluted 10-fold, and the nitric acid concentration of the diluted solution was measured using a small reflection spectrophotometer (RQ Flex 2, Merck KGaA), and the nitrate ion content in the leaf was calculated.

  The measurement results (average value: n = 3) of the nitrate ion content in the leaves are shown in FIG. 3B for green waves and in FIG. 4B for crunches.

(3) Measurement of glucose content in leaves A glucose solution was prepared every 100 ppm from 0 ppm to 1000 ppm. 3 mL of enzyme solution (glucose kit Glucose CII-Test Wako, Wako Pure Chemical Industries, Ltd.) was mixed with 1 mL of glucose solution, reacted for 5 minutes in a thermostatic chamber set at 37 ° C., and then the absorbance at 505 nm was measured and calibrated. Created a line. As a result, it was judged that measurement was possible up to about 250 ppm, and a calibration curve of 0 ppm to 200 ppm was used.

  About 1/4 of the harvested lettuce was finely chopped, stirred so that the site was uniform, and 6 g was collected in a sample bottle. Four times the amount of 99% ethanol was added and ground with a blender. The obtained extract was centrifuged at 15000 G for 5 minutes using a centrifuge. 1 mL of the supernatant was collected in a centrifugal sedimentation tube, and concentrated by centrifugation at 40 ° C. for 3 hours. 10 mL of water was added to the obtained sample and redissolved to prepare a sample.

  A mixed solution was prepared by adding 0.5 mL of acetate buffer to 0.5 mL of the sample, and maintained at 37 ° C. for 5 minutes. Thereafter, 3 mL of enzyme solution (glucose kit: “glucose CII-Test Wako”, Wako Pure Chemical Industries, Ltd.) was added to 1 mL of the mixed solution and mixed to prepare an enzyme reaction solution. The enzyme reaction solution was reacted for 5 minutes in a thermostatic bath set at 37 ° C., and then the absorbance at 505 nm was measured for the enzyme reaction solution. The measured value of absorbance was substituted into the equation obtained from the calibration curve, and the glucose content in the leaf was calculated.

  The measurement results (average value: n = 3) of the glucose content in the leaves are shown in FIG. 3 (c) for green waves and in FIG. 4 (c) for crunches.

(4) Discussion From the results of measurement of the above-ground living weight and the nitrate ion content in leaves shown in FIGS. 3 (a) and 3 (b) and FIGS. 4 (a) and 4 (b), a culture solution containing nitrate ions is obtained. It can be seen that the content of nitrate ions in the leaf is reduced in Example 1 in which the culture solution is switched to water in the dark period, as compared to Comparative Example 1 which was constantly circulated.

  Moreover, it turns out that the direction of Example 1 which switched the culture solution to water in the dark period reduces the nitrate ion content in a leaf compared with the comparative example 2 which switched the culture solution to water in the light period. From this result, even if the time when the crops are in contact with nitrate ions (the amount of nitrate ions in contact with the crops) is the same, it is possible to reduce the nitrate ion content in the leaves by switching the culture medium to water during the dark period. I understand.

  Further, from the measurement results of the leaf glucose content shown in FIG. 3C and FIG. 4C, it can be seen that the leaf glucose content increases in Example 1 as compared to Comparative Example 1 and Comparative Example 2. .

  5 and 6 are graphs showing the relationship between the nitrate ion content and the glucose content for the measurement results of Test Example 1 (n = 3) for each of the green wave and the crunch. As shown in FIGS. 5 and 6, when the slope of the regression line based on the data of Comparative Example 1 and Example 1 is compared with the slope of the regression line based on the data of Comparative Example 1 and Comparative Example 2, In both cases of wave and crunch, it can be seen that the increase rate of the glucose content with respect to the decrease of the nitrate ion content is larger in the former (Example 1) than in the latter (Comparative Example 2).

  Therefore, compared to Comparative Example 2 in which the culture solution was switched to water in the light period, Example 1 in which the culture solution was switched to water in the dark period was more effective than the reduction amount of the nitrate ion content. It is believed that the glucose content can be increased.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  1 cultivation bed, 21, 22, 23 supply valve, 31, 32, 33 discharge valve, 41 1st pump, 42 2nd pump, 51 1st tank, 52 2nd tank, 6 light source.

Claims (7)

Under a light-dark cycle including a light period in which light is applied to the crop within 24 hours and a dark period in which the light is not applied to the crop or the light is applied to the crop with less light than the light period. A hydroponics method for hydroponically cultivating crops,
A first cultivation step in which the roots of the crop are brought into contact with a first liquid containing nitrate ions;
A second cultivation step of contacting the roots of the crop with a second liquid substantially free of nitrate ions,
In the light period, the first cultivation process is performed for a time of 10% or more of the light period,
In the dark period, the hydroponics method of carrying out the second cultivation step for 50% or more of the dark period.   The hydroponic cultivation method according to claim 1, further comprising a washing step of washing a root area of the crop between the first cultivation step and the second cultivation step.   The hydroponics method according to claim 1 or 2, wherein the first liquid further includes nutrients other than the nitrate ions.   The hydroponic cultivation method according to any one of claims 1 to 3, wherein the crop is a vegetable.   The hydroponic cultivation method according to claim 4, wherein the vegetables are leaf vegetables. It is a hydroponic cultivation apparatus used for the hydroponic cultivation method of any one of Claims 1-5,
A first liquid supply device for supplying the first liquid around a root of the crop;
A hydroponic cultivation apparatus, comprising: a second liquid supply device for supplying the second liquid around a root of the crop.   The hydroponic cultivation apparatus according to claim 6, comprising a cleaning apparatus for cleaning the roots of the crops.

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