JPH0763282B2 - Automatic pH control method in hydroponics - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a method for automatically controlling the pH of a nutrient solution in the hydroponics of plants used in plant factories, institutional horticulture and the like.

[Conventional technology]

Conventional methods for automatic pH control of nutrient solution in hydroponics of plants used in plant factories and horticulture are described in, for example, Giken Information Center, seminar text "Present state and future direction of environmental control technology in hydroponics". (Yoshimi Abe, 1984
As shown in -5), the pH value of the nutrient solution was constantly controlled by introducing an acid or an alkali so that the pH value converges to a certain set value.

[Problems to be solved by the invention]

In the above-mentioned conventional technology, the pH of the nutrient solution is controlled so as to always be maintained at a certain set value, and consideration is given to the relationship between the availability and pH of many nutrient elements contained in the nutrient solution for plants. Was not taken into account, so the above relationship was taken into consideration.
There was a problem that periodic control with a wide range of realizable pH values could not be performed.

The object of the present invention is to automatically control the pH of the nutrient solution, not to control the pH value to a constant value, but to control it with a width of a sawtooth wave shape, which is available to many nutrient elements in plants. Another object of the present invention is to provide a method for automatically controlling the pH of a nutrient solution which is better for plant growth, taking into consideration the relationship between pH and pH.

[Means for solving problems]

The purpose is to provide another nutrient solution tank that intermittently discharges the nutrient solution that flows in according to two preset water levels between the cultivation tank and the nutrient solution tank in which the nutrient solution continuously circulates. This is achieved by automatically controlling the overall pH by supplying acid or alkali. In this case, the storage and drainage of the nutrient solution are repeated intermittently in the separate tank. First, while the nutrient solution is being stored, an acid or an alkali is supplied by a metering pump, and the change amount of the pH value of the nutrient solution in the tank is preliminarily measured. Next, based on this amount of change, the amount of acid or alkali necessary for pH control of the entire nutrient solution is calculated and supplied.

[Action]

Preliminarily measure the pH change amount of the nutrient solution stored in the separately provided nutrient solution tank, and calculate the amount of acid or alkali required for the overall pH control based on this measured value. Therefore,
Since it is possible to accurately know the amount of acid or alkali required to achieve the required control amount of the pH value of the entire nutrient solution at that time, (1) the rapid rise time from the set lower limit value to the upper limit value And (2) prevention of troubles caused by excessive addition of acid and alkali can be realized.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

In FIG. 1, the cultivation tank 2 for the plant 1 is the first nutrient solution tank.
3, second nutrient solution tank 4, pump for circulating nutrient solution 5, 6
And a circulation pipe 8 for the nutrient solution 7. Water level detectors 9 and 10 and a pH sensor 11 are installed in the nutrient solution tank 4, and a tank 12 containing an acid and an alkaline solution separately is connected by a metering pump 13. The nutrient solution 7 is continuously discharged from the tank 3 to the cultivation tank 2 by the pump 5, and the nutrient solution overflowing from the cultivation tank 2 flows into the tank 4 (solid arrow in the figure). In the tank 4, when the water level rises to the level 14, the pump 15 operates by the output 15 of the water level detector 9,
The nutrient solution in the tank is discharged to the tank 3. Water level is 16
When the water level drops to 0, the pump 6 is stopped by the output 17 of the water level detector 10. The intermittent discharge of the nutrient solution from the tank 4 to the tank 3 is performed before the nutrient solution 7 in the tank 3 that continuously discharges the nutrient solution is discharged, so that the capacity of the tanks 3 and 4 and the pumps 5 and 6 are
Adjust the flow rate of. When the pH of the nutrient solution drops to the lower limit (Fig. 2), the switch 18 is inserted when the water level in the tank 4 drops to 16 and the pump 6 is stopped.
Is operated, the alkali 19 in the tank 12 is supplied to the tank 4 until the water level rises to the level 14, and the pH increase amount δpH20 during this period is measured by the pH sensor 11. Meanwhile, tank 4
The amount ΔC21 of alkali supplied to the is calculated from the operating time of the metering pump 13. Let ΔV be the amount of nutrient solution when it reaches the water level 14 in tank 4, and let V be the amount of the entire nutrient solution. The amount of △ C22 is It can be calculated from the formula.

According to the present embodiment, the upper and lower limit set values of the pH control of the nutrient solution are provided, and the pH can be automatically controlled in a sawtooth waveform, from the rising of the lower limit to the upper limit until reaching equilibrium. It is also effective in shortening the time and preventing plant damage due to excessive addition of alkali (acid).

〔The invention's effect〕

According to the present invention, in the control by the supply of acid or alkali of the pH of the nutrient solution in the hydroponic culture, the amount of acid or alkali necessary for changing the unit pH of the pH of the entire nutrient solution at the present time is provided separately. Since it can be calculated using the tank, it is possible to control the upper and lower limits of the pH between two levels that are set arbitrarily in the automatic pH control of the nutrient solution, and shorten the time until the pH value reaches equilibrium. It is also effective in preventing excessive addition of acid or alkali.

[Brief description of drawings]

FIG. 1 is a system configuration diagram showing an automatic pH control method of a nutrient solution according to an embodiment of the present invention, and FIG. 2 is a diagram showing an example of a pH control pattern of the nutrient solution. 1 ... Plant, 2 ... Cultivation tank, 3,4 ... Fluid tank, 5,6 ...
… Pump, 7 …… Nutrient solution, 8 …… Nutrient solution circulation pump, 9,10…
… Water level detector, 11 …… pH sensor, 12 …… acid, alkali tank, 13 …… quantitative pump, 14,16 …… water level, 15,17
...... Water level detector output, 18 ...... Switch, 19 ...... Acid or alkali liquid, 20 ...... pH change amount, 21 ...... Acid or alkali supply amount,
22 …… Calculation formula for required amount of acid or alkali.

Claims (1)

[Claims] 1. A method for automatically controlling pH in a hydroponic culture in which a plant is cultivated while circulating the nutrient solution between a plant cultivation tank and a nutrient solution tank, wherein the pH of the nutrient solution has predetermined upper and lower limits. A method for automatically controlling pH in a hydroponic culture, which is characterized in that the values are controlled in a sawtooth waveform.