How to grow sweet potatoes in a nutrient solution

Abstract

To provide a method for solution culture of sweet potatoes that can control the content of potassium in sweet potatoes under culture while maintaining the yields.SOLUTION: A method for solution culture of sweet potatoes has: a planting step for planting seedlings of sweet potatoes on a culture bed for solution culture; an early growing step for culturing the planted seedlings by supplying the culture bed with a nutritious solution containing potassium, which is a horticulture-formulated medium diluted into a low concentration; and a late growing step for controlling the amount of potassium fertilizer supplied to the culture bed side through the nutritious solution to control the content of potassium in sweet potatoes under culture.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a method for hydroponic cultivation of sweet potato, which is capable of controlling the potassium content. [Background technology]

[0002] Sweet potatoes are one of the foods that are relatively high in potassium. Patients undergoing dialysis cannot eat much of them, but because potassium is easily dissolved in water and easily lost from the body through sweating, foods with a higher potassium content are preferred for athletes who play many sports and sweat a lot, and for astronauts who work in outer space, where body fluids are prone to becoming low in potassium and high in calcium.

[0003] In response to this, conventional methods are known, such as the hydroponic cultivation method described in Patent Document 1 for cultivating low-potassium fruits and vegetables, and the production method for low-potassium foods described in Patent Document 2, in which sweet potatoes and the like are subjected to a specified heat treatment after harvest to reduce the potassium in the food. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5622260 [Patent Document 1] Re-tabled publication No. 2018-230708 Summary of the Invention [Problem to be solved by the invention]

[0005] According to the hydroponic culture method of Patent Document 1, the amount of potassium contained in crops such as strawberries and melons being cultivated can be controlled by controlling the amount of potassium in the culture solution. However, in the case of sweet potatoes, there are differences in the cultivation method, such as the general practice of increasing potassium fertilization to suppress the so-called vine wilting phenomenon and promote the growth of tuberous roots, and therefore a similar hydroponic culture method cannot be applied to sweet potatoes. As a result, there has been a problem in that it is difficult to cultivate sweet potatoes with a controlled amount of potassium while maintaining yield.

[0006] An object of the present invention is to provide a nutrient solution culture method for sweet potatoes, which makes it possible to control the amount of potassium contained in the sweet potatoes being cultivated while maintaining the yield. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides a method for cultivating sweet potato seedlings by supplying a low-concentration nutrient solution containing potassium, which is a diluted nutrient solution prepared by using a culture medium containing potassium, to the cultivation bed. Reduce The amount of potassium fertilizer supplied to the cultivation bed side through the potassium-adjusted nutrient solution, which is a low-concentration nutrient solution, is Reduction By doing this, the amount of potassium in sweet potatoes can be increased. Reduction and a later stage of growth step of growing the plants in the late stage of the growth. The low concentration nutrient solution is characterized in that a culture solution formulated for the cultivation of the plants is used at a concentration of 20 to 30%.

[0008] The present invention is , The method includes a planting step of planting sweet potato seedlings in a cultivation bed for nutrient culture, an early growth step of cultivating the planted seedlings by supplying a low-concentration nutrient solution obtained by diluting the concentration of a culture solution formulated for a garden as a nutrient solution containing potassium to the cultivation bed, and a late growth step of controlling the amount of potassium contained in the cultivated sweet potato by controlling the amount of potassium fertilizer supplied to the cultivation bed side through a potassium-adjusted nutrient solution, which is a low-concentration nutrient solution in which the amount of potassium fertilizer is adjusted. The latter stage of growth includes: As the potassium-adjusted nutrient solution, Sweet potatoes were grown using potassium-removed nutrient solution, in which potassium had been removed from the nutrient solution. Characterized by .

[0009] The above The later stage of growth is characterized in that it starts after the earlier stage of growth is performed for 2 to 3 months. vinegar do. Effect of the Invention

[0010] They discovered that by cultivating sweet potatoes in a low-concentration nutrient solution containing potassium, which is a diluted version of the culture solution prescribed by the Oriental Plant Research Center, during the early growth stage, and then controlling the amount of potassium fertilizer contained in the low-concentration nutrient solution during the later growth stage, it is possible to control the amount of potassium contained in the harvested sweet potatoes while maintaining the yield. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing a nutrient solution cultivation apparatus for carrying out a nutrient solution cultivation method according to the present invention. [Diagram 2] 1 is a flowchart showing an example of the procedure of a sweet potato hydroponic culture method of the present invention. [Diagram 3] 1 is a table showing the yield and potassium content of harvested sweet potatoes. [Figure 4] (A) is a photograph showing the state after planting, and (B) and (C) are photographs showing the growth state 9 and 15 weeks after planting. [Diagram 5] (A) to (D) are photographs showing Beniazuma, Beniharuka, Kintoki, and Annou harvested 17 weeks after planting. [Figure 6] (A) and (B) are photographs showing side shoots obtained from sweet potatoes grown in the first cultivation cycle and the state of those side shoots after they were planted, and (C) is a photograph showing the state of the side shoots planted in the second cultivation cycle after they have taken root. [Figure 7] This is a photograph showing sweet potatoes harvested 13 weeks after planting. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] As a result of extensive research, the inventors of the present application have discovered that, when cultivating sweet potatoes in a nutrient solution, by using side shoots obtained at the time of harvesting (before or after harvesting) as seedlings for the next cultivation cycle, it is possible to shorten the cultivation cycle of sweet potatoes to about 3 to 4 months while cultivating them continuously, and that, when cultivating sweet potatoes in a nutrient solution, the amount of potassium contained in the sweet potatoes can be controlled while maintaining the yield by cultivating them in a nutrient solution using a low-concentration nutrient solution that is a diluted version of the culture solution prescribed by the orchard during the early growth stage when the stems and leaves mainly grow, and by controlling the amount of potassium fertilizer contained in the low-concentration nutrient solution during the later growth stage when the tuberous roots mainly grow.

[0013] The above-mentioned method for growing sweet potatoes in a nutrient solution will be described below with reference to the drawings. Fig. 1 is a diagram showing a nutrient solution cultivation apparatus for carrying out the nutrient solution cultivation method according to the present invention. As shown in Fig. 1, the nutrient solution cultivation apparatus 1 includes a cultivation bed 2, a solid medium for nutrient solution cultivation 3 provided in the cultivation bed 2, a mulch 4 covering the surface of the medium, and a nutrient solution supplying device 5 for supplying a predetermined nutrient solution to the medium.

[0014] The cultivation bed 2 is a box-shaped member with an open top where the solid medium is formed, and is made of a breathable material. In this embodiment, a bed that extends about 1 m in the longitudinal direction and has a capacity (solid medium) of about 25 L was used.

[0015] The solid medium 3 is formed by spreading inorganic culture soil such as perlite, rock wool, sand, and gravel in the cultivation bed 2. Instead of inorganic culture soil, organic culture soil such as coconut shells, cedar bark, and peat moss may be used as the solid culture soil.

[0016] The mulch 4 is installed so as to cover the entire surface of the solid medium provided in the cultivation bed, and sweet potato seedlings (side shoots), which will be described in detail later, are planted in the solid medium at predetermined intervals (approximately 30 cm) and holes are formed for installing the nutrient solution supply device.

[0017] By installing this Mulch 4, it is possible to prevent strong direct sunlight, which is expected to promote rooting and establishment after planting the seedlings, and it also makes it easier to turn the sweet potato vines.

[0018] The nutrient solution supplying device 5 has a supply nozzle 5a that supplies nutrient solution to the base side of the sweet potato by being inserted into the solid medium 3 in the cultivation bed 2, a tank (not shown) for storing the nutrient solution, a pump (not shown) for sending the nutrient solution in the tank to the supply nozzle side, and a control unit (not shown) for controlling the operation of the pump, and the control unit is configured to be able to freely set the amount of nutrient solution supplied to the cultivation bed side via the supply nozzle 5a and the timing of supply.

[0019] The nutrient solution supplied to the cultivation bed side by the nutrient solution supplying device 5 is a low-concentration nutrient solution obtained by diluting a generally used general-purpose culture solution, and a potassium-adjusted nutrient solution obtained by adjusting the amount of potassium fertilizer contained in the low-concentration nutrient solution. Specifically, the low-concentration nutrient solution is a culture solution diluted to a concentration of 10 to 50%, more preferably 20 to 30%.

[0020] The nutrient solution supplying device 5 may be configured so that the type of nutrient solution supplied to the cultivation bed side can be smoothly and easily changed by replacing the entire tank. Alternatively, a configuration may be adopted in which a different tank is prepared in advance for each type of nutrient solution, and the nutrient solution to be supplied is switched by an operator operating a switching tool, or the control unit may automatically switch at a predetermined date and time or timing.

[0021] The nutrient solution cultivation device 1 having the above-mentioned configuration is configured to be installed indoors where the temperature and humidity can be adjusted, or in a vinyl greenhouse, so that sweet potatoes, which can only be harvested once a year in normal soil cultivation, can be cultivated continuously all year round regardless of the season, as they are planted in around May to June and harvested in around October to November.

[0022] Below, we will explain the process of simultaneously cultivating sweet potatoes in a nutrient solution using the nutrient solution cultivation apparatus of this configuration, cultivating low-potassium sweet potatoes in which the harvested sweet potatoes contain less potassium than usual, or high-potassium sweet potatoes in which the harvested sweet potatoes contain more potassium than usual, and cultivating sweet potatoes continuously using nutrient solution cultivation, which allows sweet potatoes to be harvested three to four times a year, whereas with normal soil cultivation, sweet potatoes can only be harvested once a year.

[0023] Next, the steps of the method for hydroponic cultivation of sweet potatoes of the present invention will be described with reference to Fig. 2. Fig. 2 is a flow chart showing an example of the procedure of the method for hydroponic cultivation of sweet potatoes of the present invention. As shown in Fig. 2, first, a planting step is performed in which sweet potato seedlings are planted in the hydroponic cultivation apparatus 1 (solid medium 3) (S101).

[0024] This planting process is characterized by planting the side shoots obtained when (or before or after) harvesting sweet potatoes in the previous cultivation cycle as sweet potato seedlings. This significantly reduces the time and labor required, which takes more than a month, compared to growing sweet potato seedlings from seed potatoes.

[0025] Next, during the early growth stage, when the sweet potato stems and leaves grow, a low-concentration nutrient solution that is a diluted version of the culture solution typically used in hydroponic cultivation is supplied to the planted seedlings (S102). This early growth stage is carried out during the period when the sweet potato stems and leaves grow, so it is carried out within 2 to 3 months after the sweet potato seedlings (side shoots) are planted.

[0026] The low-concentration nutrient solution used in the early growth stage is a diluted culture solution formulated by the National Laboratory of Plant Nutrients, with the concentration being 10 to 50%, more preferably 20 to 30%. The low-concentration nutrient solution is a diluted culture solution formulated by the National Laboratory of Plant Nutrients, and contains potassium fertilizer, although at a lower concentration than usual.

[0027] Next, mainly for the later growth stage when the sweet potato tubers grow, a later growth stage step is carried out in which a potassium-adjusted nutrient solution in which the amount of potassium fertilizer contained in the low-concentration nutrient solution is adjusted is supplied (S103).

[0028] Specifically, by using a nutrient solution in which potassium fertilizer has been removed (or reduced) from a low-concentration nutrient solution as the potassium-adjusted nutrient solution supplied here, it is possible to cultivate low-potassium sweet potatoes with a lower amount of potassium than usual. On the other hand, by using a low-concentration nutrient solution similar to that used in the early growth stage, or a nutrient solution in which potassium fertilizer has been added to a low-concentration nutrient solution as the potassium-adjusted nutrient solution, it is possible to cultivate high-potassium sweet potatoes with a higher amount of potassium than usual.

[0029] Next, a seedling obtaining step is performed to obtain side shoots as seedlings to be planted in the cultivation bed in the planting step of the next cultivation cycle before harvesting (S104). Here, a procedure for obtaining seedlings (side shoots) before harvesting sweet potatoes is described, but the step of obtaining seedlings (side shoots) may be performed simultaneously with or after the harvesting step of harvesting sweet potatoes.

[0030] Next, a harvesting step is performed (S105) to harvest the sweet potatoes that have grown 13 to 17 weeks (about 3 to 4 months) after planting. According to the hydroponic cultivation method of the present invention, it is possible to grow sweet potatoes to a harvestable size in about 13 weeks (about 3 months) after planting. Specific working (experimental) examples will be described later.

[0031] Next, the sweet potato cultivation cycle can be smoothly resumed by carrying out the planting process in the N+1 (next) cultivation cycle using the side shoots obtained by the seedling obtaining process in the Nth cultivation cycle.

[0032] In this case, the N+1th cultivation cycle may be carried out by reusing the same nutrient solution cultivation apparatus 1 to carry out continuous cultivation after the cultivation bed 2 has been emptied following the completion of the harvest of the previous sweet potato, or by using a separately prepared nutrient solution cultivation apparatus 1 to carry out continuous cultivation using side shoots obtained before the harvest of the previous sweet potato.

[0033] According to the above-mentioned method of hydroponic cultivation of sweet potatoes (in which the amount of potassium can be controlled), a low-concentration nutrient solution in which the concentration of the culture solution prescribed in the orchard is diluted to a predetermined concentration is supplied during the early growth stage when the stems and leaves mainly grow, and a potassium-adjusted nutrient solution in which the amount of potassium fertilizer is changed depending on the use and purpose is supplied during the later growth stage when the tuberous roots mainly grow, thereby making it possible to harvest low-potassium or high-potassium sweet potatoes.

[0034] Furthermore, according to the above-mentioned (continuous) hydroponic cultivation method for sweet potatoes, the seedlings to be planted in the hydroponic cultivation device (cultivation bed) in the planting step are side shoots obtained from sweet potatoes cultivated in the previous cultivation cycle, and in the growth step (early and late growth stages), a low-concentration nutrient solution with a diluted concentration of the experimental culture solution is supplied, thereby shortening the cultivation cycle to about 3 to 4 months. In other words, sweet potatoes that can only be harvested once a year in normal soil cultivation can be harvested 3 to 4 times a year by using the above-mentioned hydroponic cultivation method.

[0035] In this case, in the planting process, side shoots obtained from sweet potatoes cultivated in the immediately preceding cultivation cycle are used as the seedlings to be planted in the nutrient solution cultivation apparatus, so that it is no longer necessary to grow the seedlings from seed potatoes over a period of about one month, thereby shortening the cultivation cycle by about one month.

[0036] According to the above-described hydroponic cultivation method, the amount of potassium contained in the cultivated sweet potatoes can be controlled, and the sweet potatoes can be harvested three to four times a year. EXAMPLES

[0037] Next, a specific example of the above-mentioned method for hydroponic cultivation of sweet potatoes in which the potassium content can be controlled will be described with reference to Figures 3 to 5. Figure 3 is a table showing the yield and potassium content of harvested sweet potatoes, Figure 4(A) is a photograph showing the state after planting, Figures 4(B) and (C) are photographs showing the growth state 9 weeks and 15 weeks after planting, and Figures 5(A) to (D) are photographs showing Beniazuma, Beniharuka, Kintoki, and Annou harvested 17 weeks after planting.

[0038] In this embodiment, four varieties of sweet potato, namely, Beniazuma, Beniharuka, Kintoki, and Anna, were used as the targets (varieties) for the above-mentioned hydroponic cultivation using the hydroponic cultivation apparatus.

[0039] First, 25 L of perlite was spread on the cultivation beds 2, which were extended by about 1 m in the longitudinal direction, to form a solid culture soil, and 2 to 3 sweet potato seedlings (side shoots) were planted in a line in the longitudinal direction on each of the cultivation beds 2. Furthermore, the supply nozzle 5a of the nutrient solution supplying device 5 was buried in the perlite so that the nutrient solution was supplied to the base of each planted plant (see the planting process (May 27), FIG. 4(A)).

[0040] Next, the sweet potato seedlings were grown by continuously supplying 200 ml of low-concentration nutrient solution, which was made by diluting the culture solution formulated for the garden experiment to 25%, to the base of the planted plants using the nutrient solution supplying device 5 at a timing of 13 times per day (early growth stage process, see FIG. 4(B)).

[0041] Next, the following areas were set up: a zone in which the supply of potassium fertilizer was stopped by switching from the low-concentration nutrient solution to a potassium-adjusted nutrient solution in which the potassium fertilizer had been removed (potassium-removed nutrient solution) 9 weeks after planting (July 29th) (hereafter, the 2-month supply zone); a zone in which the supply of potassium fertilizer was stopped by switching from the low-concentration nutrient solution to a potassium-adjusted nutrient solution in which the potassium fertilizer had been removed (potassium-removed nutrient solution) 13 weeks after planting (August 25th) (hereafter, the 3-month supply zone); and a zone in which the supply of potassium fertilizer continued by continuing to supply low-concentration nutrient solution from planting to harvest (hereafter, the continuous supply zone) (late growth process, see Figure 4(C)).

[0042] Next, the sweet potatoes were harvested all at once 17 weeks after planting (September 23rd) (harvesting process, Figures 5(A) to (D)). After that, the yield of each variety of sweet potato harvested in each supply area was investigated, and the potassium content of each variety of sweet potato harvested in each supply area was compared with the standard value for potassium in raw potatoes (see Figure 3). The results are explained below.

[0043] As shown in Figure 3, the yield per sweet potato plant did not decrease significantly even when the supply of potassium fertilizer was stopped from the later growth stage, and some varieties (Beniharuka and Anna) even had higher yields. Furthermore, sweet potato plants were grown by supplying a low-concentration nutrient solution with less potassium from the early growth stage, but there was no significant change in the leaf color of the sweet potatoes, and the leaves did not turn yellow as occurs with potassium deficiency (see Figures 4 (B) and (C)).

[0044] Furthermore, regarding the potassium content of sweet potatoes, in the approximately four-month cultivation period from planting to harvest, in the two-month supply area where the supply of potassium fertilizer was stopped in the last two months, the potassium content was reduced by nearly 50% compared to the standard value for raw potatoes. Also, in the three-month supply area where the supply of potassium fertilizer was stopped in the last month, the potassium content was reduced by about 10-20% compared to the standard value for raw potatoes. Note that for the Anno variety only, the potassium content was higher than the standard even with a three-month supply (see Figure 3).

[0045] Furthermore, in the continuous supply area where potassium fertilizer was supplied continuously using a low-concentration nutrient solution from planting to harvest, the potassium content of all varieties was higher than the standard value for raw potatoes, although the amount of increase varied depending on the variety (see Figure 3).

[0046] Based on the above, it was shown that the amount of potassium contained in the harvested sweet potatoes can be controlled by adjusting the amount of potassium fertilizer supplied via the nutrient solution (especially during the later stages of growth) during hydroponic cultivation (perlite cultivation).

[0047] Specifically, the sweet potato hydroponic cultivation method of the present invention makes it possible to grow low-potassium sweet potatoes for dialysis patients by stopping the supply of potassium fertilizer via the nutrient solution in the later growth stage, and the amount of potassium reduced in the sweet potatoes can also be controlled by controlling the timing for stopping the supply of potassium fertilizer (within 2 to 3 months after planting).

[0048] On the other hand, in the case of the method of cultivating sweet potatoes in a nutrient solution according to the present invention, if low-concentration fertilizer containing potassium is continuously supplied during the growth process (early and late growth stages), the amount of potassium tends to be higher than that of sweet potatoes grown in normal soil cultivation, making it possible to produce high-potassium sweet potatoes for athletes and astronauts. Among the above varieties, Anna is considered to be the one that is most susceptible to the effects of controlling the amount of potassium fertilizer in the nutrient solution supplied. EXAMPLES

[0049] Next, a specific embodiment of the method for continuously cultivating sweet potatoes using nutrient solution culture will be described with reference to Figures 3 to 7, with reference to the differences from the above-mentioned embodiment. Figures 6(A) and (B) are photographs showing side shoots obtained from sweet potatoes grown in the first cultivation cycle and the state of the side shoots after planting, Figure 6(C) is a photograph showing the state of the side shoots planted in the second cultivation cycle after they have taken root, and Figures 7(A) and (B) are photographs showing sweet potatoes harvested 13 weeks after planting.

[0050] Continuous cultivation of sweet potatoes by the above-mentioned nutrient solution cultivation is performed using the nutrient solution cultivation apparatus 1 under the same conditions as in Example 1. First, sweet potato seedlings (side shoots) are planted in the cultivation bed 2 in the same manner as in Example 1 (planting step).

[0051] As in Example 1, sweet potato seedlings were grown by continuously supplying 200 ml of a low-concentration nutrient solution containing potassium, which was prepared by diluting the culture solution formulated for the garden experiment to 25%, to the base of the planted plants using the nutrient solution supplying device 5 13 times per day (early and late growth stages, see Figures 4(B) and (C)).

[0052] Next, 17 weeks after planting (September 23rd), just before the sweet potatoes were harvested en masse, side shoots were obtained from the sweet potato vines as seedlings to be planted in the next cultivation cycle (see Figure 6(A)).

[0053] Next, while the seedlings would normally be planted after the moisture had evaporated, the second cultivation cycle was started by immediately planting the side shoots (seedlings) without allowing the moisture to evaporate from the side shoots (see Figure 6(B)).

[0054] As a result, as shown in Figure 6(C), the seedlings (side shoots) of all the varieties tested (Beniazuma, Beniharuka, Kintoki, and Anna) took root and showed good growth. This is thought to be because, unlike soil culture, hydroponic culture constantly maintains an appropriate amount of moisture in the solid medium (perlite), and because a low-concentration nutrient solution made by diluting the culture solution prescribed by the experiment was used, the side shoots were able to root smoothly.

[0055] Generally, when the nutrient solution is highly concentrated in hydroponic cultivation, the high temperatures of summer make the roots prone to rot, so the nutrient solution is usually replaced with water to encourage root growth. However, according to the cultivation method of the present invention, a low-concentration nutrient solution made by diluting the culture solution prescribed by the Enshitsu Experiment Station to 25% was used in the growth process, so it is believed that the roots grew without any root rot.

[0056] As a result, when sweet potatoes are continuously cultivated using the nutrient solution cultivation apparatus, side shoots obtained from sweet potatoes grown in the immediately preceding cultivation cycle can be used as seedlings to be planted, eliminating the need for the effort and time required to grow seedlings from seed potatoes, and allowing sweet potato cultivation to be restarted smoothly.

[0057] Incidentally, even when sweet potatoes were harvested 13 weeks (approximately 3 months) after planting, as shown in Figures 7(A) and (B), seven sweet potatoes (with a maximum weight of 688 g) were harvested from one plant, which were slightly smaller than the sweet potatoes harvested 17 weeks after planting.

[0058] According to the above, by carrying out the above-mentioned continuous nutrient solution cultivation method for sweet potatoes in a vinyl greenhouse (room), the cultivation cycle from planting seedlings (side shoots) to harvesting sweet potatoes can be carried out in 3 to 4 months, and this cultivation cycle can be carried out seamlessly and continuously. Therefore, according to the continuous cultivation method for sweet potatoes of the present invention, sweet potatoes can be harvested 3 to 4 times a year.

Claims

1. A planting process of planting sweet potato seedlings in a cultivation bed for hydroponics; A growth stage step of cultivating the planted seedlings by supplying a low-concentration nutrient solution obtained by diluting the concentration of a culture solution formulated for gardening to the cultivation bed as a nutrient solution containing potassium; A late-stage growth step of reducing the amount of potassium contained in the sweet potato being cultivated by reducing the amount of potassium fertilizer supplied to the cultivation bed side through a potassium-adjusted nutrient solution, which is a low-concentration nutrient solution in which the amount of potassium fertilizer is reduced; having The low-concentration nutrient solution used was a nutrient solution with a concentration of 20 to 30%. A method for hydroponic cultivation of sweet potato, comprising the steps of:

2. A planting process of planting sweet potato seedlings in a cultivation bed for hydroponics; A growth stage step of cultivating the planted seedlings by supplying a low-concentration nutrient solution obtained by diluting the concentration of a culture solution formulated for gardening to the cultivation bed as a nutrient solution containing potassium; A late growth step of controlling the amount of potassium fertilizer supplied to the cultivation bed side through a potassium-adjusted nutrient solution, which is a low-concentration nutrient solution in which the amount of potassium fertilizer is adjusted, thereby controlling the amount of potassium contained in the sweet potato being cultivated; having In the latter stage of growth, sweet potatoes were grown using a potassium-removed nutrient solution in which potassium had been removed from the nutrient solution as the potassium-adjusted nutrient solution. A method for hydroponic cultivation of sweet potato, comprising the steps of:

3. The late growth stage begins 2 to 3 months after the early growth stage. The method for hydroponic cultivation of sweet potato according to claim 2.

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