KR20180037451A - The hydroponic methods for leafy vegetables production with a low nitrate or potassium content - Google Patents

Abstract

The present invention relates to a hydroponic method of leafy vegetables, and to leafy vegetables produced by using the method, and more specifically, to a hydroponic method of leafy vegetables with low nitric acid or potassium content, which comprises a step for applying a hydroponic culture solution composition, which does not contain a nitrogen source or a potassium source for a period of time prior to cultivation, and to leafy vegetables produced by using the method. By using the hydroponic method of the leafy vegetables with low nitric acid or potassium content, according to the present invention, it is possible to cultivate the leafy vegetables having a reduced content only in nitric acid or potassium without significantly affecting the overall yield of the leafy vegetables and other nutrients. In addition, a problem of hydroponics which produce leafy vegetables with excessively high nitrate content has been solved, and it is possible to supply low-potassium leafy vegetables to kidney disease patients.

Description

Technical Field [0001] The present invention relates to a hydroponic culture method for producing low-acid or low-

The present invention relates to a hydroponic cultivation method of a low-acid or low-potassium leafy vegetable and a leaf vegetable produced using the same. More particularly, the present invention relates to a hydroponic cultivation composition containing no nitrogen source or potassium source for a predetermined period before harvest And a low-acid or low-potassium leafy vegetable produced by the method.

Hydroponic cultivation is a scientific farming technology in which plants are cultivated by using a culture solution in which various inorganic nutrients required for the growth of various plants including crops are dissolved at an appropriate concentration. As technology for cultivating plants without being affected by the soil to be. The advantage of the hydroponic cultivation is that it can directly observe the state of the roots and the growth pattern, produce clean polluted vegetables and crops, easily grow in the house, and decorate the house. Using these hydroponic cultivation techniques can increase the yield of agricultural products, minimize environmental burden, and reduce labor force.

Another advantage of the hydroponic cultivation method is that the nutrients necessary for the growth of plants and their functions are compared with the plants cultivated by hydroponics when the nutrients are grown in a nutrient solution containing nutrients. It is to be able to know. The nutrients and their functions required for the growth of these plants are unusual when growing plants in the soil and are a particular advantage of the hydroponic cultivation method.

In Korea, hydroponic cultivation has been started with the use of culture media since 1980, and now it is widely used for cultivating various plants such as cabbage, radish, cucumber, tomato, pepper, lettuce, parsley, have.

On the other hand, leafy vegetables are an item of a method of classifying vegetables, collectively referred to as leafy vegetables such as cabbage, cabbage, lettuce, spinach and the like, and also referred to as leafy vegetables, and the leafy vegetables are also plants capable of hydroponics.

However, since hydroponic cultivation of the leaf vegetables uses most of the nitrogen source in the culture liquid as NO ₃ -N form, it is urgently required to develop a technique for reducing the nitrate content in vegetables. Especially, in the case of plant factories using artificial light, in order to reduce the production cost, leaf vegetables are mainly produced in low light condition. In this case, the activity of nitrogen denaturation enzyme is lowered due to low light, and the nitrate content in the body becomes too high.

Patients with kidney disease are also at increased risk of hyperkalemia due to the difficulty in excretion of potassium if they consume excessive amounts of potassium-rich summer fruits or vegetables. Therefore, in order to prevent the patients with chronic kidney disease from being exposed to the risk such as hyperkalemia, a method of producing a low-potassium leafy vegetables by applying a nutrient solution having a low potassium content in the production of leaf vegetables by hydroponics, Despite this desperate need, there is a lot of lack of relevant research.

In addition, as has been described in the above-mentioned merits of hydroponic cultivation, it is known that when a specific component is subtracted from the culture solution, the content of the specific component is reduced in the plant, but the nitrogen and potassium are essential nutrients for the growth of plants, In the case of producing leafy vegetables from the beginning, there is a problem that the total growth of leafy vegetables is remarkably lowered by the law of minimum rate.

Therefore, there is a desperate need to develop a hydroponic cultivation method of leaf vegetables containing nitrogen or potassium evenly with the nutrients other than nitrogen or potassium without affecting the growth of leafy vegetables by properly supplying the nitrogen or potassium into the culture medium. The reality is that research is lacking.

As a prior art document related to the present invention, there is Korean Patent Laid-Open No. 10-2006-0052739 (hereinafter referred to as "Patent Document 1"). Patent Document 1 discloses a nutrient solution composition for containing a high concentration of germanium in plants and a method of cultivating a plant using the nutrient composition. However, regarding the hydroponic cultivation method in which the remaining nutrients are evenly distributed without affecting the growth of leafy vegetables, Or even implied.

Under these circumstances, the present inventors have made extensive efforts to develop a production method of a low-acid or low-potassium leafy vegetable that does not affect the content of the remaining nutrients except for nitrogen or potassium without affecting the growth of the leafy vegetables. The present inventors completed the present invention by confirming that the content of nitric acid and potassium in the cultivated leaf vegetables decreased when the nitrogen source or the potassium source was not supplied for a certain period of time before harvesting.

Patent Document 1: Korean Patent Publication No. 10-2006-0052739

The main object of the present invention is to provide a hydroponic culture method of low-acid or low-potassium leafy vegetables.

Another object of the present invention is to provide a low-acid or low-potassium leafy vegetable produced by the hydroponic cultivation method.

The present inventors have conducted various studies to develop a hydroponic culture method of leaf vegetables having no influence on the body content of nutrients other than nitrogen or potassium without affecting the overall growth of leafy vegetables, It was found that the content of nitrate or potassium in the leafy vegetables grown without affecting the overall growth and the content of the remaining nutrients was lowered.

Specifically, the present inventors predicted that the nitrogen or potassium content in the harvested leaf vegetables could be reduced by not adding a nitrogen source or a potassium source to the culture composition during the hydroponic cultivation of the leaf vegetables. However, Or by the 'law of minimum rate', which is determined by the nutrient, the total production of leaf vegetables is significantly reduced. In addition, it was confirmed that the total growth of leafy vegetables was lowered by the law of minimum rate, and not only the nitrogen or potassium but also the content of other nutrients in the leaf vegetables was remarkably reduced.

Accordingly, the present inventors have conducted various studies to develop a hydroponic culture method of leaf vegetables that do not affect the content of the remaining nutrients without reducing the total production amount. The inventors of the present invention have found that when a nitrogen source or a potassium source It was confirmed that the total yield of leaf vegetables could be secured and that the content of the remaining nutrients did not significantly affect the content of leaf vegetables.

As described above, the inventors of the present invention have found that discontinuing the supply of the nitrogen source or the potassium source at a specific time does not significantly affect the total yield of the leafy vegetables and the content of the remaining nutrients.

In one embodiment, the present invention provides a method for cultivating a leaf vegetable by hydroponically cultivating leaf vegetables by adding a culture composition for hydroponic cultivation (a); And (b) cultivating the hydroponic cultivation composition containing no nitrogen source 3 to 7 days before harvesting the cultivated leafy vegetables, or cultivating the hydroponic cultivation composition containing no potassium source 6 to 11 days before harvest And a method of hydroponically cultivating a low-acid or low-potassium leafy vegetable including the step

The term "hydroponic cultivation method" of the present invention means a method of cultivating a plant by using a nutrient solution (nutrient solution or culture solution) containing minerals or other ions without using soil.

In the present invention, the hydroponic cultivation method is not particularly limited, but may be interpreted as a method used for growing leafy vegetables.

The term " leafy vegetables " of the present invention means vegetables that mainly use the part of leaves or stems. The above-described leaf vegetables are not particularly limited as long as they can be cultivated by a hydroponic cultivation method, but examples thereof include lettuce, watermelon, spinach, sausage, sausage, chrysanthemum, cabbage, Chinese cabbage, mustard, kale, herb , Basil, etc.) and the like.

The term " composition for cultivation for hydroponic cultivation " of the present invention means nutrient solution containing minerals or other ions supplied to plants for hydroponic cultivation.

The culture composition (which means the initial culture composition before stopping the supply of the nitrogen source or the potassium source) may contain any of the essential nutrients necessary for not lowering the overall growth of the leafy vegetables, Specifically, the culture composition before the stop of feeding of the nitrogen source is added to the nitrogen source with ammonium monophosphate (NH ₄ H ₂ PO ₄ ), potassium monophosphate (KH ₂ PO ₄ ), potassium sulfate K ₂ SO ₄ ), magnesium sulfate (MgSO ₄揃 7H ₂ O), and chelate iron (Fe-EDTA, Fe-DTPA). In addition, the culture medium composition before the injection of the potassium source interruption is calcium nitrate 4 beard to the potassium source _{[Ca (NO 3) 2 ·} 4H 2 O], calcium nitrate 10 beard _{{5 [Ca (NO 3)} 2 · 2H ₂ O] NH ₄ NO ₃ }, ammonium monophosphate (NH ₄ H ₂ PO ₄ ), magnesium nitrate [Mg (NO ₃ ) ₂ .6H ₂ O], ammonium nitrate (NH ₄ NO ₃ ), magnesium sulfate ₄ · 7H ₂ O) and chelate iron (Fe-EDTA, Fe-DTPA), and satisfies the law of minimum rate required for growing leafy vegetables.

The term " nitrogen source " in the present invention means a nutrient contained in a culture medium for hydroponic cultivation by acting as a nitrogen source, and the nitrogen source includes calcium nitrate quat [Ca (NO ₃ ) ₂ .4H ₂ O] 10 beard _{{5 [Ca (NO 3)} 2 · 2H 2 O] · NH 4 NO 3]}, potassium nitrate (KNO _3), ammonium nitrate (NH ₄ NO ₃₎ and magnesium nitrate [Mg (NO _{3) 2} · 6H ₂ O].

The term " potassium source " in the present invention means a nutrient contained in the culture medium of hydroponic cultivation by acting as a potassium source. The potassium source is potassium nitrate (KNO ₃ ), potassium monophosphate (KH ₂ PO ₄ ) Potassium sulfate (K ₂ SO ₄ ), and the like.

In the hydroponic cultivation method of the present invention, there is no particular limitation on the luminous intensity condition, but specifically, the hydroponic cultivation with a luminous intensity of 100 to 300 μmol · m ^-2 s ^-1 reduces the content of nitrate or potassium in the utmost , The overall growth rate can be maximized and the effect on the body content of other nutrients can be minimized. In particular, it is possible to achieve the best effect by cultivating the plant in a water-based culture at a light intensity of 200 to 300 μmol · m ^-2 s ^-1 .

In the hydroponic cultivation method of the present invention, the cultivation period is a period necessary for harvesting and growing the leafy vegetables so that they can be consumed for food, and the total cultivation period for hydroponics of the present invention is specifically 23 to 30 days (More specifically, an average of 25 days).

When the nutrient source is stopped 3-7 days prior to harvest or when the potassium source is discontinued 6-11 days before harvest, the culture composition containing the above components is added to the hydroponic culture of leafy vegetables, It may be possible to harvest leafy vegetables.

However, the introduction of a nitrogen source or a potassium source in the above-mentioned period is required to stop harvesting a low-quality acid or a low-potassium leafy vegetable, and the overall yield is not significantly affected as compared with the case where the supply of the nitrogen source or the potassium source is not stopped, It does not affect the body's content of other nutrients. In addition, in the case of stopping the feeding at a time earlier than the above-mentioned stopping time, the total production amount is lowered compared to stopping the feeding in the above period, and the content of other nutrients significantly affects the body, .

In another aspect, the present invention provides a low-acid or low-potassium leafy vegetable produced by the hydroponic cultivation method.

The leaf vegetable cultivated by the hydroponic cultivation method contains nitric acid or potassium in the leaf vegetable with a low content, while the total production amount and other nutrient contents of the leaf vegetable are not changed as compared with the leaf vegetable produced by the conventional hydroponic cultivation method.

For example, in the case of the low-quality leafy vegetables, the nitrogen content in the leaf vegetables is 15 to 63 times higher than that of the leaf vegetables produced by stopping the introduction of the nitrogen source after the introduction of the leaf vegetables or the nitrogen source, % ≪ / RTI > by weight.

In addition, the low-potassium leaf vegetables have a nitrogen content in the leaf vegetables reduced to 44 to 72% by weight, compared with the leaf vegetables produced by stopping the introduction of the potassium source after stopping the introduction of the leaf vegetables or the potassium source without stopping the potassium source Lt; / RTI >

According to the present invention, it is possible to cultivate leafy vegetables having reduced nitric acid or potassium content without affecting the overall yield of leaf vegetables and other nutrients by using the hydroponic culture method of low-acid or low-potassium leafy vegetables. This effect also solves the problem of hydroponics, which produces too high nitrate content in leafy vegetables, and it can supply low potassium fertilizer to kidney disease patients.

FIG. 1 is a graph showing changes in the growth of the lettuce in a case where cultivation of the lettuce is controlled by controlling the feeding of the nitrogen source by the hydroponic cultivation method provided in the present invention, wherein (a) shows the result of comparing the leaf area of the lettuce , (b) shows the comparison of fresh weight of lettuce, and (c) shows the result of comparing the nitrate content in the lettuce.
FIG. 2 is a graph showing a change in the content of nitrate in leaf vegetables according to the stopping time and intensity of the nitrogen source when the feeding of nitrogen source is controlled by the hydroponic cultivation method provided by the present invention. ) Shows the change in the nitrate content in the body with time and intensity of the nitrogen source, and (b) shows the change in nitrate content in the body according to the light intensity according to the stopping time of the nitrogen source.
FIG. 3 is a photograph showing the results of growth depending on the time and intensity of stopping the introduction of the nitrogen source when the feeding of the nitrogen source is controlled and the cultivation of the lettuce is carried out by the hydroponic cultivation method provided by the present invention.
FIG. 4 is a graph comparing changes in contents of potassium in leafy vegetables according to the time when the supply of potassium source is stopped when the flowering of potatoes is controlled by controlling the input of potassium source by the hydroponic cultivation method provided by the present invention.

Hereinafter, the present invention will be described in detail with reference to the following examples. However, the following examples are only for illustrating the present invention, and the scope of the present invention is not limited by the following examples.

Example  One: Leafy  Analysis of effect of stoppage of nitrogen source in culture medium during hydroponic cultivation

Example  1-1: Stop feeding nitrogen source

Giving type bok choy, cheongchima lettuce and integral skirt while grown in a culture medium containing nitrate lettuce cultivation was fed a nutrient solution that does not contain nitrate nitrogen (NO ₃ -N) before harvesting 5-7 days. Specifically, the standard nutrient solution for vegetable garden by hydroponic cultivation at the time of hydroponics cultivation (see Table 1 to Table 3, Table 1 is a large element equivalence table (me / L) of the standard vegetable cultivar for the development of the National Horticultural Research Institute (Horticultural Garden) (G / ton), and Table 3 shows a trace element composition table (g / ton) of a standard culture of leaf vegetables for leaf vegetables), and it was found that 5-7 days before harvesting, (Ca (NO ₃ ) ₂ .4H ₂ O], calcium nitrate 10 hydrate {5 [Ca (NO ₃ ) ₂ .2H ₂ O] NH ₄ NO ₃ ]}, potassium nitrate (KNO ₃ ) Ammonium nitrate (NH ₄ NO ₃ ), and magnesium nitrate [Mg (NO ₃ ) ₂ .6H ₂ O]. The light intensity of the hydroponic cultivation plant was adjusted to 100 to 300 μmol · m ^-2 s ^-1 .

Example  1-2: Chinchilla  Measurement of growth and nitrate content changes

Growth changes (Fig. 1) and nitrate contents (Fig. 2) of the lettuce were measured by adjusting the nutrient solution before the feeding of the nitrogen source before harvesting. In particular, a Control group was untreated in Figure 1, TW is a group with the nutrient solution and the settlement processing group with nutrient solution and stop water processing, 1 / 2S; means a group treated drainage 1/2 standard concentration of the nutrient solution and, NO ₃ - N removal means the group treated with NO ₃ -N in the nutrient solution, and (NH ₄ ) ₂ CO ₃ means the group treated with ammonium carbonate in the nutrient solution. FIG. 2 also shows the results of stopping the supply of the nitrogen source for each light intensity.

Meanwhile, FIG. 1 shows changes in the growth of the lettuce of the cheongmach in accordance with the nutrient solution in which the feeding of the nitrogen source before the harvest is stopped. Specifically, Fig. 1 (a) compares the leaf area of the lettuce with the nitrogen source, Fig. 1 (b) compares the fresh weight of the lettuce with the nitrogen source, (C) compares the nitrate content of the body of lettuce with the nitrogen source stopped.

On the other hand, the growth characteristics of the lettuce cultivated according to the nutrient solution adjusting method 7 days before harvest are shown in Table 4.

FIG. 2 is a graph showing changes in the luminous intensity and the nitrate content in the body depending on the time of stopping the input of the nitrogen source before harvest. Specifically, Fig. 2 (a) shows the change in nitrate content in the body according to the time when the supply of the nitrogen source is stopped, and Fig. 2 (b) shows the luminous intensity [100 M ² s ^-1 ), 200 (100 μmol · m ^-2 s ^-1 ) and 300 (300 μmol · m ^-2 s ^-1 )], respectively.

1 and 2, the results shown in Table 5 were obtained.

Specifically, in Table 5, the nitrate content can be minimized by stopping the supply of the nitrogen source in the nutrient solution seven days before the harvest, and when the photometric condition is taken into consideration, harvesting at 200 to 300 μmol · m ^-2 s ^-1 The effect of reducing the nitrate content in the body was the highest when the supply of the nitrogen source was stopped 3 days ago. In addition, the total amount of growth showed the highest growth by stopping the supply of nitrogen source 3 days before harvest. In the case of vitamin content, the supply of nitrogen source was most stopped at the time of 3 to 5 days of harvest.

3 is a graph showing the relationship between the luminosities (100, 200, and 300 μmol · m ^-2 s ^-1 ) in the plant plant and the number of days before the harvest (7d), 5 days (5d), and 3 days This is a photograph showing the growth of lettuce.

In order to prevent the addition of nitrate nitrogen (NO ₃ -N) in the nutrient solution 7 days prior to harvesting in the cultivation of aquaculture seeds, cheongcham lettuce, and red skins lettuce, calcium nitrate 4 hydrate [Ca (NO ₃ ) ₂ .4H ₂ O ], calcium nitrate 10 beard _{{5 [Ca (NO 3)} 2 · 2H 2 O] · NH 4 NO 3]}, potassium nitrate (KNO _3), ammonium nitrate (NH ₄ NO _3), magnesium nitrate [Mg (NO ₃ ) ₂ · 6H ₂ O] was added to the nutrient solution, it was confirmed that nitrate could be reduced by 63.3% without decreasing the growth rate. This pattern was similar to the absence of the nitrogen source 5 days before harvest and the absence of the nitrogen source 3 days prior to harvest could significantly reduce the nitrate content.

In addition, in the case of cultivation of abandoned lettuce in a plant using artificial light, when the supply of nutrients was stopped 3 days before harvest at a light intensity of 300 μmol · m ^-2 s ^-1 , the growth and the vitamin C content were the highest without deteriorating the external quality, The effect of reducing nitrate in the body can be seen.

When these results are summarized, it was confirmed that the time of stopping the input of the nitrate supply source, which can maximize the nitrate reduction effect while the content of other nutrients such as vitamin C is high without decreasing the growth amount, is between 3 and 7 days.

On the other hand, Table 6 shows the results of growth of the lettuce in the light condition and the amount of the nutrient solution before harvest.

Example  2: Leafy  Cultivation at hydroponic cultivation My T  Analysis of effect by stopping supply of source

Example  2-1: Stop the supply of potassium source

(KNO ₃ ), potassium phosphate (KH ₂ PO ₄ ), or sulfuric acid (KH ₂ PO ₄ ) as a source of potassium in a certain period before harvesting, Potassium (K ₂ SO ₄ ) -free nutrient solution was prepared and supplied.

Example  2-2: Tangy  Measurement of growth and potassium content changes

As a result of measurement of potassium content and growth rate of tsumba vegetable (Chungchima lettuce, ssamushi, Cheonggyeongchae) according to the stopping time of potassium source, the effect of decreasing the potassium content in the plant body was generally longer as the period without potassium was longer, . Especially, when potassium was replaced with potassium solution 11 days before harvest, the potassium content in the body decreased by 71.9% on average compared to the non - nutrient solution, and the fresh weight was somewhat reduced, but the growth was secured to some extent.

The results are shown in FIG. 4 and Table 7. 4 (K settlement time: 11d (before harvest 11 days), 6d (before harvest 6 days), control (no treatment) As shown in FIG. 4, when the potassium source was stopped 11 days before harvest, it was confirmed that the potassium content was reduced to a maximum level. In the case where the potassium source was stopped in the earlier period, Respectively.

Meanwhile, Table 7 below shows the results of measuring the growth of various kinds of vegetables in accordance with the time when the supply of potassium source is stopped. As shown in the following Table 7, it can be confirmed that stopping the input of the potassium source 6 days before harvesting significantly increases the live weight and the growth amount compared with the case where the potassium source is stopped 11 days before harvest. From FIG. 4, it was confirmed that the effect of reducing the potassium content in the body was not greater than that of stopping the supply of the potassium source 11 days before harvest, but the content thereof could be reduced by about 50% as compared with the control group. However, when the supply of potassium source was stopped sooner than 6 days before harvest, it was confirmed that the effect of reducing the potassium content in the body dropped rapidly to 30% or less of potassium in the body of the control group.

From these results, it was confirmed that the stopping time of the potassium source, which does not significantly decrease the potassium content in the body but also the growth rate, is 6-11 days before harvest.

From the above description, it will be understood by those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. In this regard, it should be understood that the above-described embodiments are to be considered in all respects as illustrative and not restrictive. The scope of the present invention should be construed as being included in the scope of the present invention without departing from the scope of the present invention as defined by the appended claims.

Claims (9)

In the hydroponic cultivation method of leaf vegetables,
(a) hydroponically growing leaf vegetables by adding a culture composition for hydroponic cultivation; And
(b) adding a hydroponic cultivation composition containing no nitrogen source 3 to 7 days before harvesting the cultivated leafy vegetables, or adding a hydroponic cultivation composition containing no potassium source 6 to 11 days before harvesting And a method of hydroponically cultivating low-potassium acid or low-potassium leafy vegetables.
The method according to claim 1,
Culture medium composition before the injection of the nitrogen source interruption is first ammonium phosphate _{(NH 4 H 2 PO 4)} , a first of potassium phosphate (KH ₂ PO _4), potassium sulfate (K ₂ SO ₄₎ to the nitrogen source, And at least one selected from the group consisting of magnesium sulfate (MgSO ₄ .7H ₂ O) and chelate iron (Fe-EDTA, Fe-DTPA)
Culture medium composition before the injection of the potassium source interruption is calcium nitrate 4 beard to the potassium source _{[Ca (NO 3) 2 ·} 4H 2 O], calcium nitrate 10 beard _{{5 [Ca (NO 3)} 2 · 2H 2 O] NH ₄ NO _3}, first ammonium phosphate _{(NH 4 H 2 PO 4)} , magnesium nitrate _{[Mg (NO 3) 2 ·} 6H 2 O], ammonium nitrate (NH ₄ NO _3), magnesium sulfate (MgSO ₄ 7H ₂ O) and chelate iron (Fe-EDTA, Fe-DTPA).
The method according to claim 1,
The nitrogen source is selected from the group consisting of calcium nitrate quat [Ca (NO ₃ ) ₂ .4H ₂ O], calcium nitrate 10 hydrate {5 [Ca (NO ₃ ) ₂ .2H ₂ O] NH ₄ NO ₃ ] KNO ₃ ), ammonium nitrate (NH ₄ NO ₃ ) and magnesium nitrate [Mg (NO ₃ ) ₂ .6H ₂ O].
The method according to claim 1,
Wherein the potassium source is at least one selected from the group consisting of potassium nitrate (KNO ₃ ), potassium monophosphate (KH ₂ PO ₄ ) and potassium sulfate (K ₂ SO ₄ ).
The method according to claim 1,
Wherein the hydroponic cultivation method is carried out under a light condition of 100 to 300 μmol · m ^-2 s ^-1 .
The method according to claim 1,
Wherein the cultivation period of the hydroponic cultivation method is 23 to 30 days.
A low-acid or low-potassium leafy vegetable produced by the hydroponic cultivation method according to any one of claims 1 to 6.
8. The method of claim 7,
The nitrogen content in the leaf vegetables is reduced by 15 to 63% by weight compared to the leaf vegetables produced by stopping the supply of the nitrogen source in addition to the stopping of the introduction of the leaf vegetables or the nitrogen source, Leafy vegetables.
8. The method of claim 7,
Wherein the potassium source is not discontinued and the potassium content in the leaf vegetables is reduced by 44 to 72% by weight compared to the produced leaf vegetables by stopping the introduction of the potassium source in addition to the produced leaf vegetables or the supply stop period of the potassium source. .

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