Soil pf value measuring method, and irrigation control method and irrigation control device

An apparatus for cultivation with a nutrient solution comprising:

• a continuous drip applicator of a nutrient;
• means equipped with a nutrient flow valve for controlling the supply of the nutrient from the drip applicator;
• an instrument for measuring the volumetric water content of a medium;
• a processor which is loaded with a predetermined correlation between pF value and volumetric water content of the medium, which performs arithmetic operations for conversion to pF value from the volumetric water content of the medium as measured with the instrument for measuring the volumetric water content and which outputs a signal for the pF value of the medium on the basis of the result as outputted from the instrument for measuring the volumetric water content;
• and
• means for controlling the drip applicator by controlling the supply of the nutrient to the drip applicator on the basis of a signal for pF value as outputted from said processor.

An apparatus for cultivation with a nutrient solution comprising:

• a continuous drip applicator of a nutrient;
• means equipped with a nutrient flow valve for controlling the supply of the nutrient from the drip applicator;
• a sensor from among an amplitude-domain reflectometry (ADR) instrument, a time-domain reflectometry (TDR) instrument and an frequency-domain reflectometry (FDR) instrument each having a probe to be inserted into a medium;
• a processor which is loaded with two predetermined correlations for the medium, one being between pF value and volumetric water content and the other being between the output signal value from the sensor and the volumetric water content, which performs arithmetic operations for conversion from the output signal value of the sensor to the volumetric water content of the medium and for conversion to pF value from the volumetric water content of the medium and which outputs a signal for the pF value of the medium on the basis of the output signal value of the sensor;
• and
• means for controlling the drip applicator by controlling the supply of the nutrient to the drip applicator on the basis of a signal for pF value as outputted from said processor.