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

• US 20030024155A1
• Filed: 06/24/2002
• Published: 02/06/2003
• Est. Priority Date: 12/22/1999
• Status: Active Grant

• Current Assignee: Ebara Corporation
• Original Assignee: Ebara Corporation
• Inventors: Kamiya, Ichiro, Narasaki, Yuzo, Otsuka, Hidemitsu, Kuroda, Tetsuo
• Granted Patent: US 6,719,488 B2
• Time in Patent Office: Days
• US Class Current: 47/1.01R
• CPC Class Codes: A01G 25/167 Control by humidity of the soil itself or of devices simulating soil or of the atmosphere; Soil humidity sensors
• CPC Class Codes: G01N 2033/245 for agricultural purposes
• CPC Class Codes: G01N 22/04 Investigating moisture content
• CPC Class Codes: G01N 33/24 Earth materials G01N33/42 takes precedence

Abstract

The invention aims at providing a method and an apparatus for measuring the moisture content of the soil in order to enable pF value based control of irrigation in cultivation on the soil, as well as a method and an apparatus which use the first-mentioned method and apparatus to enable pF value based control of irrigation. To attain these objects, the invention provides a method for measuring the pF value (soil moisture tension) of the soil, comprising the steps of (a) preliminarily determining the correlation between pF value and volumetric water content of the soil to be measured, (b) measuring the volumetric water content of the soil, and (c) converting the value of the volumetric soil water content of the soil measured in the above step (b) to the corresponding pF value on the basis of the correlation between pF value and volumetric water content predetermined in the above step (a). The invention also provides a method and an apparatus for controlling the irrigation of the soil based on the measurement of the pF value by said method.

Claims

1. A method for measuring the pF value (soil moisture tension) of the soil, comprising the steps of:

(a) preliminarily determining the correlation between pF value and volumetric water content of the soil to be measured;

(b) measuring the volumetric water content of the soil; and

(c) converting the value of the volumetric water content of the soil measured in the above step (b) to the corresponding value on the basis of the correlation between pF value and volumetric water content predetermined in the above step (a).

2. The method according to claim 1, wherein the volumetric water content of the soil is measured by ADR method, TDR method or FDR method.

3. The method according to claim 2, wherein the correlation between the output signal value of a sensor selected from among an ADR instrument, a TDR instrument or an FDR instrument and the volumetric water content of the soil is preliminarily determined for the soil to be measured and the output signal value obtained with the sensor is converted to the volumetric water content of the soil on the basis of the preliminarily determined correlation between the output signal value and the volumetric water content of the soil.

4. The method according to claim 3, wherein two predetermined correlations for the soil to be measured, one being between pF value and volumetric water content and the other being between the output signal value of the sensor and the volumetric water content, are loaded into a processor and the conversion from the output signal value of the sensor to the volumetric water content of the soil and the conversion to pF value from the volumetric water content of the soil are performed with the processor by arithmetic operations.

5. The method for measuring the pF value of the soil according to any one of claims 1-4, wherein the soil is coarse soil composed of large particles having porous surfaces, said step (a) comprises the sub-steps of:

(i) pulverizing a sample of the coarse soil to prepare a fine particulate sample;

(ii) mixing the sample of the coarse soil and the fine particulate sample in a predetermined weight ratio to prepare a mixed soil sample;

(iii) determining the correlation between the volumetric water content and the pF value for both the mixed soil sample and the fine particulate sample; and

(iv) determining the correlation between the volumetric water content and the pF value for the coarse soil sample on the basis of the correlations between the volumetric water content and the pF value obtained for the mixed soil sample and the fine particulate sample.

6. The method according to claim 5, wherein the coarse soil is pumice.

7. The method according to claim 5 or 6, wherein the correlations between the volumetric water content and the pF value for the mixed soil sample and the fine particulate sample are determined by the pressure-plate method or the sand-column method.

8. A method for controlling irrigation of the soil which, on the basis of the pF value of the soil as measured by the method according to any one of claims 1-7, controls the amount of supply of irrigating water or nutrient such that the soil will have a pF value appropriate for crop cultivation.

9. The method for controlling irrigation of the soil according to claim 8 which comprises measuring the pF value of the soil at a timer-determined period and controlling the amount of supply of irrigating water or nutrient on the basis of the measured pF value of the soil.

10. 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.

11. 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 selected from among an ADR instrument, a TDR instrument and an 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.