Soil diagnosis method, irrigation control method, and irrigation control device

Abstract

To provide a soil diagnosis method capable of determination as to whether a plow layer is appropriate by using a soil evaluation pF value using a WFPS, and to provide an irrigation control method and an irrigation control device that can maintain soil in the most appropriate wet condition.SOLUTION: A soil diagnostic method includes: a soil moisture characteristic measurement step of performing measurement for soil moisture from undisturbed sample soil collected from soil A where irrigation management is performed, or the undisturbed sample soil and disturbed sample soil collected from the soil A; a soil evaluation pF value determination step of determining a pF value corresponding to a set WFPS value as a soil evaluation pF value, from a measured value obtained in the soil moisture characteristic measurement step; and a soil diagnosis step of diagnosing the soil A by using the soil evaluation pF value. In the soil diagnosis step, when the soil evaluation pF value is within a first set range, the soil A is determined to be an appropriate plow layer in which water is easily retained, and when the soil evaluation pF value exceeds the first set range, the soil A is determined to be an inappropriate plow layer in which water absorption stress is concerned if oxygen supply is to be normalized.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a soil diagnosis method for irrigation management, an irrigation control method using a soil evaluation pF value determined by this soil diagnosis method, and an irrigation control device for performing this irrigation control method.

Background Art

[0002] The applicant of the present application has proposed a roofing material installation method capable of preventing rain from entering while allowing wind to enter, a rain shield roof structure for plant cultivation, a rain shield roof structure for plant cultivation, an asparagus cultivation system, and an asparagus cultivation method (Patent Document 1). When using such a rain shield roof structure, especially when cultivating asparagus under conditions with good drainage such as frame plate type high ridge cultivation, appropriate irrigation management is important. Generally, a tensiometer or a matric potential sensor is used, and irrigation management is often performed based on the detected pF value (for example, Patent Document 2). In addition, Patent Document 3 proposes measuring the oxygen concentration in the soil and suppressing irrigation when the measured oxygen concentration becomes equal to or lower than a predetermined value.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] As a result of conducting tests, the applicant of the present application has obtained the knowledge that the pF value set for the irrigation start point must be varied depending on the soil. As described in Patent Document 2, the pF value can be directly measured in the field, and it is known that the pF value suitable for crop cultivation is between 1.7 and 2.7. Although the pF value as the irrigation start point suitable for the field varies depending on the cultivated variety, it is said not to depend on the soil. The applicant of the present application has found that the pF value corresponding to the soil moisture content equivalent to 60% WFPS, which is known as the critical wet state where oxygen supply is restricted, varies greatly depending on the soil. By performing irrigation management based on the pF value using WFPS as an index, the applicant has obtained the knowledge that the soil can maintain the most appropriate wet state. WFPS (Water-Filled Pore Space) is an index that simultaneously considers the quantitative ratio of water and air distributed in the pores of the soil, and is obtained by dividing the volumetric water content by the porosity. In addition, WFPS is an index used in the fields of soil microbiology and microbial ecology. In research on evaluating greenhouse gas emissions from soil, the volumetric water content may be converted to WFPS, but it is an index that cannot be measured in the field and is not used in the fields of irrigation engineering and soil physics. In Patent Document 2, since it may be difficult to measure the pF value for soils composed of coarse particles, it is proposed to measure the volumetric water content of the soil and obtain the pF value from the measured volumetric water content, but it does not propose a pF value suitable for the soil. In addition, Patent Document 3 considers that not only water but also air (oxygen) is important for supporting plant growth, but since it does not consider the characteristics of the soil, the suitability or unsuitability as a growing medium can only be known retrospectively, and appropriate irrigation management cannot be performed depending on the soil quality. Also, according to the applicant's actual measurement, the change in oxygen concentration is slow, and it is difficult to control irrigation based on the change in oxygen concentration.

[0005] Therefore, an object of the present invention is to provide a soil diagnosis method capable of determining whether the soil is an appropriate growing medium or an inappropriate growing medium based on the soil evaluation pF value using WFPS, and to provide an irrigation control method and an irrigation control device capable of maintaining the soil in the most appropriate wet state.

Means for Solving the Problems

[0006] The soil diagnosis method of the present invention according to claim 1 is a soil diagnosis method for irrigation management, comprising a soil moisture characteristic measurement step of measuring soil moisture for an undisturbed sample soil collected from soil A for which the irrigation management is to be performed, or from the undisturbed sample soil and a disturbed sample soil collected from soil A; a soil evaluation pF value determination step of determining, as a soil evaluation pF value, a pF value corresponding to a set WFPS value from the measurement values obtained in the soil moisture characteristic measurement step; and a soil diagnosis step of diagnosing soil A based on the soil evaluation pF value determined in the soil evaluation pF value determination step. In the soil diagnosis step, if the soil evaluation pF value is within a first set range, soil A is determined to be appropriate soil for retaining water, and if the soil evaluation pF value exceeds the first set range, soil A is determined to be inappropriate soil for which there is concern about water absorption stress when attempting to optimize oxygen supply. The present invention according to claim 2 is the soil diagnosis method according to claim 1, wherein in the soil moisture characteristic measurement step, for the undisturbed sample soil, the relationship between the pF value and the volumetric water content is measured, and a first soil moisture characteristic curve calculation step of calculating a pF value - volumetric water content curve from the measurement values obtained in the soil moisture characteristic measurement step; a WFPS calculation step of calculating WFPS from the measured volumetric water content and the porosity of the undisturbed sample soil; and a second soil moisture characteristic curve calculation step of calculating a pF value - WFPS curve from the pF value - volumetric water content curve calculated in the first soil moisture characteristic curve calculation step and the WFPS calculated in the WFPS calculation step. In the soil evaluation pF value determination step, the pF value - WFPS curve calculated in the second soil moisture characteristic curve calculation step is used to determine the soil evaluation pF value. The present invention according to claim 3 is the soil diagnosis method according to claim 1, wherein in the soil water characteristic measurement step, for the undisturbed sample soil, from the water content weight measured at capillary saturation and the dry weight measured after drying, the volumetric water content and dry density at the capillary saturation are calculated, for the disturbed sample soil, the true specific gravity is calculated by the pycnometer method, and an entrapped air ratio calculation step of calculating the entrapped air ratio using the volumetric water content, the dry density, and the true specific gravity at the capillary saturation calculated in the soil water characteristic measurement step is provided. In the soil evaluation pF value determination step, with the square root conversion value of the entrapped air ratio calculated in the entrapped air ratio calculation step as the root entrapped air ratio, the soil evaluation pF value is determined by the formula a + b × root entrapped air ratio (where a and b are coefficients). It is characterized by being determined by the following formula. The present invention according to claim 4 is the soil diagnosis method according to claim 1, wherein in the soil water characteristic measurement step, for the undisturbed sample soil, the saturated hydraulic conductivity is calculated by a saturated permeability test. In the soil evaluation pF value determination step, with the common logarithm value of the saturated hydraulic conductivity calculated in the soil water characteristic measurement step as LogKsat, the soil evaluation pF value is determined by the formula a + c × LogKsat (where a and c are coefficients). The invention according to claim 5 is the soil diagnosis method according to claim 1, wherein in the soil moisture characteristic measurement step, for the undisturbed sample soil, from the water content weight measured by capillary saturation and the dry weight measured after drying, the volumetric water content and dry density at the time of capillary saturation are calculated, and the saturated hydraulic conductivity is calculated by a saturated permeability test. For the disturbed sample soil, the true specific gravity is calculated by the pycnometer method, and an enclosed air rate calculation step is provided for calculating the enclosed air rate using the volumetric water content, the dry density, and the true specific gravity at the time of capillary saturation calculated in the soil moisture characteristic measurement step. In the soil evaluation pF value determination step, the square root conversion value of the enclosed air rate calculated in the enclosed air rate calculation step is used as the root enclosed air rate, the common logarithm value of the saturated hydraulic conductivity calculated in the soil moisture characteristic measurement step is used as LogKsat, and the soil evaluation pF value is determined by the formula a + b × root enclosed air rate + c × LogKsat + d × root enclosed air rate × LogKsat (where a, b, c, and d are coefficients). The invention according to claim 6 is the soil diagnosis method according to any one of claims 1 to 5, wherein in the soil diagnosis step, if the soil evaluation pF value is below the first set range, it is characterized in that the soil A is determined to be a soil that is difficult to retain moisture and requires small and frequent irrigation. The irrigation control method of the invention according to claim 7 is an irrigation control method using the soil evaluation pF value determined by the soil diagnosis method according to any one of claims 1 to 5. The soil evaluation pF value is used as a monitoring value, and a pF value detection sensor 1 is installed in the soil A from which the undisturbed sample soil is taken. Irrigation is started when the detected pF value detected from the pF value detection sensor 1 becomes the monitoring value. The irrigation control device 10 of the invention according to claim 8 is an irrigation control device 10 that performs the irrigation control method according to claim 7, and is characterized in that the detected pF value and the monitoring value are compared, and when the detected pF value becomes the monitoring value, the irrigation device 2 is caused to start irrigation. The irrigation control device 10 of the present invention according to claim 9 compares the detected pF value detected by the pF value detection sensor 1 installed in the soil A with a preset monitoring value, and when the detected pF value reaches the monitoring value, causes the irrigation device 2 to start irrigation. The irrigation control device 10 uses the soil evaluation pF value as the monitoring value, and sets the soil evaluation pF value as the pF value corresponding to the set WFPS value of WFPS in the pF value-WFPS curve. The pF value-WFPS curve is calculated from the pF value-volumetric water content curve based on the measured values of the undisturbed sample soil collected from the soil A, and the WFPS based on the volumetric water content and porosity of the undisturbed sample soil.

Effect of the Invention

[0007] According to the soil diagnosis method of the present invention, by determining the soil evaluation pF value using WFPS, which is an index considering water and air simultaneously, it is possible to judge whether the soil is properly prepared or not based on this soil evaluation pF value. For improperly prepared soil, soil improvement can be promoted before cultivating crops. Further, according to the irrigation control method or irrigation control device of the present invention, since irrigation management can be performed based on the pF value using WFPS as an index, the soil can be maintained in the most appropriate wet state.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0009] The soil diagnosis method according to the first embodiment of the present invention includes a soil moisture characteristic measurement step of measuring soil moisture for an undisturbed sample soil collected from soil for irrigation management or from an undisturbed sample soil and a disturbed sample soil collected from the soil, and a soil evaluation pF value determination step of determining, as a soil evaluation pF value, a pF value corresponding to a set WFPS value from the measurement values obtained in the soil moisture characteristic measurement step. In the soil diagnosis step, if the soil evaluation pF value is within the first set range, the soil is determined to be appropriate soil for water retention, and if the soil evaluation pF value exceeds the first set range, the soil is determined to be inappropriate soil for which there is concern about water absorption stress when attempting to optimize oxygen supply. According to the present embodiment, by determining the soil evaluation pF value using WFPS, which is an index that considers water and air simultaneously, it is possible to determine whether the soil is appropriate or inappropriate soil based on this soil evaluation pF value, and for inappropriate soil, soil improvement can be promoted before cultivating crops.

[0010] The second embodiment of the present invention is the soil diagnosis method according to the first embodiment, in which, in the soil moisture characteristic measurement step, for the undisturbed sample soil, the relationship between the pF value and the volumetric water content is measured, and a first soil moisture characteristic curve calculation step of calculating a pF value - volumetric water content curve from the measurement values obtained in the soil moisture characteristic measurement step, a WFPS calculation step of calculating WFPS from the measured volumetric water content and the porosity of the undisturbed sample soil, and a second soil moisture characteristic curve calculation step of calculating a pF value - WFPS curve from the pF value - volumetric water content curve calculated in the first soil moisture characteristic curve calculation step and the WFPS calculated in the WFPS calculation step. In the soil evaluation pF value determination step, it is determined as the soil evaluation pF value using the pF value - WFPS curve calculated in the second soil moisture characteristic curve calculation step. According to the present embodiment, although the measurement in the soil moisture characteristic measurement step takes a considerable amount of time, a more accurate soil evaluation pF value can be determined.

[0011] The third embodiment of the present invention is the soil diagnosis method according to the first embodiment. In the soil moisture characteristic measurement step, for the undisturbed sample soil, the volumetric water content at capillary saturation and the dry density are calculated from the water content weight measured at capillary saturation and the dry weight measured after drying. For the disturbed sample soil, the true specific gravity is calculated by the pycnometer method. An enclosed air rate calculation step is provided to calculate the enclosed air rate using the volumetric water content at capillary saturation, the dry density, and the true specific gravity calculated in the soil moisture characteristic measurement step. In the soil evaluation pF value determination step, the square root conversion value of the enclosed air rate calculated in the enclosed air rate calculation step is used as the root enclosed air rate, and the soil evaluation pF value is determined by the formula a + b × root enclosed air rate (where a and b are coefficients). According to this embodiment, the soil evaluation pF value can be estimated without requiring a time equivalent to the measurement in the soil moisture characteristic measurement step.

[0012] The fourth embodiment of the present invention is the soil diagnosis method according to the first embodiment. In the soil moisture characteristic measurement step, for the undisturbed sample soil, the saturated hydraulic conductivity is calculated by a saturated permeability test. In the soil evaluation pF value determination step, the common logarithm value of the saturated hydraulic conductivity calculated in the soil moisture characteristic measurement step is used as LogKsat, and the soil evaluation pF value is determined by the formula a + c × LogKsat (where a and c are coefficients). According to this embodiment, the soil evaluation pF value can be estimated without requiring a time equivalent to the measurement in the soil moisture characteristic measurement step.

[0013] The fifth embodiment of the present invention is the soil diagnosis method according to the first embodiment. In the soil moisture characteristic measurement step, for the undisturbed sample soil, from the water content weight measured at capillary saturation and the dry weight measured after drying, the volumetric water content at capillary saturation and the dry density are calculated. At the same time, the saturated hydraulic conductivity is calculated by a saturated permeability test. For the disturbed sample soil, the true specific gravity is calculated by the pycnometer method. An enclosed air rate calculation step is provided to calculate the enclosed air rate using the volumetric water content at capillary saturation, the dry density, and the true specific gravity calculated in the soil moisture characteristic measurement step. In the soil evaluation pF value determination step, the square root conversion value of the enclosed air rate calculated in the enclosed air rate calculation step is used as the root enclosed air rate, the common logarithm value of the saturated hydraulic conductivity calculated in the soil moisture characteristic measurement step is used as LogKsat, and the soil evaluation pF value is determined by the formula a + b × root enclosed air rate + c × LogKsat + d × root enclosed air rate × LogKsat (where a, b, c, and d are coefficients). According to this embodiment, the soil evaluation pF value can be estimated without requiring a time equivalent to the measurement in the soil moisture characteristic measurement step.

[0014] The sixth embodiment of the present invention is the soil diagnosis method according to any one of the first to fifth embodiments. In the soil diagnosis step, if the soil evaluation pF value is below the first set range, the soil is determined to be a soil type that is difficult to retain moisture and requires small and frequent irrigation. According to this embodiment, since it is possible to determine that the soil is a soil type that is difficult to retain moisture and requires small and frequent irrigation, it is possible to pre-determine whether it is suitable for the crop to be cultivated, and it is possible to promote soil improvement and crop variety change as necessary.

[0015] The irrigation control method according to the seventh embodiment of the present invention is an irrigation control method using the soil evaluation pF value determined by the soil diagnosis method according to any one of the first to fifth embodiments. The soil evaluation pF value is used as a monitoring value, a pF value detection sensor is installed in the soil from which the undisturbed sample soil is collected, and irrigation is started when the detected pF value detected by the pF value detection sensor becomes the monitoring value. According to this embodiment, since irrigation management can be performed based on the pF value using WFPS as an index, the soil can be maintained in the most appropriate wet state.

[0016] The irrigation control device according to the eighth embodiment of the present invention is an irrigation control device that performs the irrigation control method according to the seventh embodiment. It compares the detected pF value with the monitored value, and when the detected pF value becomes the monitored value, it causes the irrigation device to start irrigation. According to the present embodiment, since irrigation management can be performed based on the pF value using WFPS as an index, the soil can be maintained in the most appropriate wet state.

[0017] The irrigation control device according to the ninth embodiment of the present invention is an irrigation control device that compares the detected pF value detected from a pF value detection sensor installed in the soil with a preset monitored value, and when the detected pF value becomes the monitored value, it causes the irrigation device to start irrigation. It uses the soil evaluation pF value as the monitored value, sets the soil evaluation pF value as the pF value corresponding to the set WFPS value of WFPS in the pF value-WFPS curve, and the pF value-WFPS curve is calculated from the pF value-volumetric water content curve based on the measured values of undisturbed sample soil taken from the soil, WFPS based on the volumetric water content and porosity of the undisturbed sample soil. According to the present embodiment, since irrigation management can be performed based on the pF value using WFPS as an index, the soil can be maintained in the most appropriate wet state.

Example

[0018] Hereinafter, a soil diagnosis method, an irrigation control method, and an irrigation control device according to an embodiment of the present invention will be described. FIG. 1 is a graph showing the concept of the present invention. FIG. 1(a) is a graph showing the relationship between WFPS and the pF value, and FIG. 1(b) is a graph showing the pF value viewed from gas diffusibility. When asparagus, which causes root rot under over-wet conditions, is used as a crop, 60% WFPS, which is known as the critical wet state where oxygen supply is restricted, is set as the set WFPS value. When the set WFPS value exceeds 60% WFPS, oxygen deficiency occurs. Further, when the pF value corresponding to the set WFPS value (60% WFPS in FIG. 1(a)) is 2.7 or more, it is improper soil preparation where water absorption stress is a concern when trying to optimize oxygen supply to the soil, and soil preparation management by tillage or compost mixing is required.

[0019] As shown in Fig. 1(a), the present invention associates WFPS that cannot be measured in the field with pF values that can be measured in the field, and determines the soil evaluation pF value by using WFPS, which is an index considering water and air simultaneously. By judging whether the soil is suitable or unsuitable for cultivation based on this soil evaluation pF value, and performing irrigation management based on the pF value with WFPS as an index. By judging whether the soil is suitable or unsuitable for cultivation based on the soil evaluation pF value, for unsuitable soil, soil improvement can be promoted before cultivating crops. In Fig. 1, the set WFPS value is described as 60% WFPS, which is known as the critical wet state where oxygen supply is restricted. However, for crops that prefer a wet state that is not overly wet, such as asparagus, the set WFPS value can be determined within the range of 55% - 65%. For example, if the crop is strawberry, it can be 70% WFPS, and the set WFPS value can be changed according to the type of crop.

[0020] The relative gas diffusion coefficient (Ds / Da) shown in Fig. 1(b) is the gas diffusion coefficient in soil / the gas diffusion coefficient in the atmosphere. The ratio of the gas diffusion coefficient of oxygen in water to that in the atmosphere (Dw / Da) is (2.60×10 -9 ) / (1.80×10 -5 ), that is, about 0.0001. The gas diffusion coefficient of oxygen in water is 10,000 times smaller than that of oxygen in the atmosphere. The relative gas diffusion coefficient at pF0.0 considered by the ε^3 model is 6.4×10 -5 , and the relative gas diffusion coefficient at pF2.0 (pF60% WFPS of this soil) is 8.0×10 -2 . Compared with the waterlogged state, the gas diffusion coefficient at 60% WFPS is 1250 times larger. In this way, the irrigation start value (monitoring value) considering gas diffusion can be determined by WFPS.

[0021] FIG. 2 is an explanatory diagram showing a soil diagnosis method according to an embodiment of the present invention. FIG. 2(a) is a flowchart showing the soil diagnosis method according to the embodiment, FIG. 2(b) is a graph showing the relationship between the measured pF value and the volumetric water content, FIG. 2(c) is a graph showing the calculated pF value-volumetric water content curve, FIG. 2(d) is a graph showing the calculated pF value-WFPS curve, and FIG. 2(e) is a graph showing the pF value corresponding to the set WFPS value using the pF value-WFPS curve.

[0022] In the soil water characteristic measurement step in S1, for the undisturbed sample soil collected from the soil for irrigation management, the relationship between the pF value and the volumetric water content is measured. The relationship between the measured pF value and the volumetric water content is a graph as shown in, for example, FIG. 2(b). In the first soil water characteristic curve calculation step in S2, a pF value-volumetric water content curve is calculated using a computer from the measurement values obtained in the soil water characteristic measurement step (S1). The calculated pF value-volumetric water content curve is a graph as shown in, for example, FIG. 2(c). In the WFPS calculation step in S3, WFPS is calculated using a computer from the measured volumetric water content and the porosity of the undisturbed sample soil. WFPS is the volumetric water content divided by the porosity. In the second soil water characteristic curve calculation step in S4, a pF value-WFPS curve is calculated using a computer from the pF value-volumetric water content curve calculated in the first soil water characteristic curve calculation step (S2) and the WFPS calculated in the WFPS calculation step (S3). The calculated pF value-WFPS curve is a graph as shown in, for example, FIG. 2(d). In the soil evaluation pF value determination step in S5, using the pF value-WFPS curve calculated in the second soil water characteristic curve calculation step (S4), the pF value corresponding to the set WFPS value of WFPS is determined as the soil evaluation pF value. The pF value corresponding to the set WFPS value can be determined using the pF value-WFPS curve as shown in, for example, FIG. 2(e). In the soil diagnosis step in S6, the soil is diagnosed based on the soil evaluation pF value determined in the soil evaluation pF value determination step (S5).

[0023] In the soil diagnosis step (S6), if the soil evaluation pF value is within the first set range, the soil is determined to be appropriate soil for water retention, and if the soil evaluation pF value exceeds the first set range, the soil is determined to be inappropriate soil where there is concern about water absorption stress when trying to optimize oxygen supply, and if the soil evaluation pF value is below the first set range, the soil is determined to be soil for which it is difficult to retain moisture and requires small and frequent irrigation. These determinations can be made using a computer. Here, the first set range is in the range of 1.8 to 2.7. If the soil evaluation pF value is within the range of 1.8 to 2.7, since water is easily retained in the soil, management is by large - quantity and small - frequency irrigation. If the soil evaluation pF value is below 1.8, since water is difficult to retain in the soil, management is by small - quantity and large - frequency irrigation. If the soil evaluation pF value exceeds 2.7, there is concern about water absorption stress when waiting for sufficient drainage to promote oxygen supply, so improvement of drainage can be promoted by soil improvement through tillage or compost mixing. Thus, since the suitability of the soil for cultivation can be judged based on water retention and oxygen supply, it is possible to judge in advance whether it is suitable for the crop to be cultivated, and it is possible to promote necessary soil improvement or change of crop variety, etc.

[0024] Figure 3 is a graph corresponding to Fig. 2(e) and shows an evaluation example by the soil diagnosis method of this embodiment. Fig. 3(a) shows the case where the soil evaluation pF value is below 1.8, Fig. 3(b) shows the case where the soil evaluation pF value is within the range of 1.8 to 2.7, and Fig. 3(c) shows the case where the soil evaluation pF value exceeds 2.7.

[0025] Figure 4 is a conceptual diagram showing an irrigation control device according to an embodiment of the present invention. The irrigation control device 10 according to this embodiment includes a control unit 11 that compares the detected pF value detected by the pF value detection sensor 1 installed in the soil A with a preset monitoring value, an output unit 12 that causes the irrigation device 2 to start irrigation when the control unit 11 determines that the detected pF value becomes the monitoring value, and a storage unit 13 that stores the monitoring value.

[0026] The pF value detection sensor 1 is installed in the soil A in the ridge (field) where the undisturbed sample soil is collected. For the pF value detection sensor 1, for example, a tensiometer or a matric potential sensor can be used. The pF value detection sensor 1 is preferably installed so that the sensor part is located at a depth of 20 cm to 40 cm from the soil surface. The irrigation device 2 performs an irrigation operation according to start and end signals from the output unit 12. The end signal from the output unit 12 can be generated using the detected pF value from the pF value detection sensor 1, or the irrigation control device 10 can be provided with a timer unit to generate the end signal by the timer unit. Note that by providing the irrigation device 2 with a timer function, the irrigation device 2 can also perform the end of the irrigation operation. As the operation means 3, for example, a mobile terminal or a mobile tablet can be used. Note that the irrigation control device 10 may include the operation means 3, the irrigation control device 10 may include the pF value detection sensor 1, and furthermore, the irrigation device 2 may include the irrigation control device 10.

[0027] Preferably, the storage unit 13 stores data such as the detected pF value, the start time of the irrigation operation for the irrigation device 2, or the irrigation operation period. When such data is stored in the storage unit 13, it is preferable to perform data browsing and data collection by the operation means 3. The monitoring value stored in the storage unit 13 is stored by an input operation from the operation means 3. It is preferable that the monitoring value can be changed by an input operation from the operation means 3. For the monitoring value, the soil evaluation pF value is used. The soil evaluation pF value is the pF value corresponding to the set WFPS value of WFPS in the pF value-WFPS curve. The pF value-WFPS curve is calculated from the pF value-volume water content curve based on the measured values of the undisturbed sample soil taken from Soil A, and WFPS based on the volume water content and porosity of the undisturbed sample soil.

[0028] Thus, the irrigation control device 10 according to this embodiment compares the detected pF value with the monitoring value, and when the detected pF value becomes the monitoring value, it causes the irrigation device 2 to start irrigation. By performing irrigation management based on the pF value using WFPS as an index, Soil A can be maintained in the most appropriate wet state. Also, the irrigation control method according to this embodiment uses the soil evaluation pF value determined by the soil diagnosis method as the monitoring value, installs the pF value detection sensor 1 in Soil A from which the undisturbed sample soil has been taken, and starts irrigation when the detected pF value detected from the pF value detection sensor 1 becomes the monitoring value. Since irrigation management can be performed based on the pF value using WFPS as an index, Soil A can be maintained in the most appropriate wet state.

[0029] FIG. 5 is a flowchart showing a soil diagnosis method according to another embodiment of the present invention. FIG. 5(a) shows the case of using the root-encapsulated air ratio, FIG. 5(b) shows the case of using LogKsat, and FIG. 5(c) shows the case of using both the root-encapsulated air ratio and LogKsat.

[0030] The soil diagnosis method shown in FIG. 5(a) will be described. In the soil moisture characteristic measurement step in S11, for the undisturbed sample soil taken from Soil A for which irrigation management is to be performed, from the water content weight measured at capillary saturation and the dry weight measured after drying, the volume water content (m 3 / m 3 ) at capillary saturation and the dry density (Mg / m 3 ) are calculated, and for the disturbed sample soil, the true specific gravity (Mg / m 3 ) is calculated using a computer by the pycnometer method. Note that the undisturbed sample soil used in the soil moisture characteristic measurement step (S11) is preferably collected at a depth of 30 cm or more from the surface layer. The soil A shallower than 30 cm is likely to have a sparse soil filling degree. The air entrapment ratio (m 3 / m 3 ) In the calculation step, the air entrapment ratio is calculated using a computer, using the volumetric water content at capillary saturation, dry density, and true specific gravity calculated in the soil moisture characteristic measurement step (S11). The air entrapment ratio = porosity - volumetric water content at capillary saturation, and The air entrapment ratio = 1 - (dry density / true specific gravity) - volumetric water content at capillary saturation.

[0031] In the soil evaluation pF value determination step in S15, using the square root conversion value of the air entrapment ratio calculated in the air entrapment ratio calculation step (S12) as the root air entrapment ratio, the soil evaluation pF value is a + b × root air entrapment ratio (where a and b are coefficients) is determined by the formula of. According to this embodiment, the soil evaluation pF value can be estimated without requiring a time equivalent to the measurement in the soil moisture characteristic measurement step (S11).

[0032] The soil diagnosis method shown in Fig. 5(b) will be described. In the soil moisture characteristic measurement step in S21, for the undisturbed sample soil, the saturated hydraulic conductivity (Ksat (cm / s)) is calculated using a computer by a saturated permeability test. Note that also in this embodiment, the undisturbed sample soil used in the soil moisture characteristic measurement step (S21) is preferably collected at a depth of 30 cm or more from the surface layer. In the soil evaluation pF value determination step in S25, using the common logarithm value of the saturated hydraulic conductivity calculated in the soil moisture characteristic measurement step (S21) as LogKsat, the soil evaluation pF value is a + c × LogKsat (where a and c are coefficients) is determined by the formula of. According to this embodiment, the soil evaluation pF value can be estimated without requiring a time equivalent to the measurement in the soil moisture characteristic measurement step (S21).

[0033] The soil diagnosis method shown in Fig. 5(c) will be described. Further, as shown in Fig. 5(c), it is more effective to use the root enclosure air ratio shown in Fig. 5(a) and the LogKsat shown in Fig. 5(b). In the soil moisture characteristic measurement step in S31, for the undisturbed sample soil collected from the soil A for irrigation management, from the water content weight measured at capillary saturation and the dry weight measured after drying, the volume water content at capillary saturation (m 3 / m 3 ) and the dry density (Mg / m 3 ) are calculated, and the saturated hydraulic conductivity (Ksat (cm / s)) is calculated using a computer by a saturated permeability test. For the disturbed sample soil, the true specific gravity (Mg / m 3 ) is calculated using a computer by the pycnometer method. In this embodiment as well, the undisturbed sample soil used in the soil moisture characteristic measurement step (S31) is preferably collected at a depth of 30 cm or more from the surface layer. In the enclosed air ratio (m 3 / m 3 ) calculation step in S12, the enclosed air ratio is calculated using a computer by using the volume water content at capillary saturation, the dry density, and the true specific gravity calculated in the soil moisture characteristic measurement step (S31). The enclosed air ratio = the porosity - the volume water content at capillary saturation, and the enclosed air ratio = 1 - (dry density / true specific gravity) - the volume water content at capillary saturation.

[0034] In the soil evaluation pF value determination step in S35, the square root conversion value of the enclosed air ratio calculated in the enclosed air ratio calculation step (S12) is used as the root enclosed air ratio, and the common logarithm value of the saturated hydraulic conductivity calculated in the soil moisture characteristic measurement step (S31) is used as LogKsat. The soil evaluation pF value is a + b×√(enclosed air rate) + c×LogKsat + d×√(enclosed air rate)×LogKsat (where a, b, c, and d are coefficients) is determined by the following equation. According to this embodiment, the soil evaluation pF value can be estimated without requiring a time equivalent to the measurement in the soil moisture characteristic measurement step.

[0035] FIG. 6 is a graph showing the verification results of the model equation used in the soil diagnosis method shown in FIG. 5. FIG. 6(a) shows the verification results based on the soil data at a depth of 30 cm, and FIG. 6(b) shows the verification results obtained by applying the parameters obtained in FIG. 6(a) to the soil A shallower than 30 cm depth.

[0036] In the graph shown in FIG. 6, the relationship between the measured value obtained by the method of FIG. 2 and the predicted value obtained by the method of FIG. 6 within the range of the soil evaluation pF value from 0.5 to 3.0 is shown, with the measured value on the horizontal axis and the predicted value on the vertical axis. "LogKsat" is the soil evaluation pF value using the common logarithm value of the saturated hydraulic conductivity, and "√(enclosed air)" is the soil evaluation pF value using the square root conversion value of the enclosed air rate. Also, "LogKsat + √(enclosed air)" is the soil evaluation pF value using the common logarithm value of the saturated hydraulic conductivity and the square root conversion value of the enclosed air rate, and the soil evaluation pF value is determined by the equation a + b×enclosed air rate + c×LogKsat (where a, b, and c are coefficients). Also, "LogKsat × √(enclosed air)" is the soil evaluation pF value including the product of the common logarithm value of the saturated hydraulic conductivity and the square root conversion value of the enclosed air rate as a variable, and the soil evaluation pF value is determined by the equation a + b×enclosed air rate + c×LogKsat + d×enclosed air rate×LogKsat (where a, b, c, and d are coefficients). Also, "StepwiseAIC" is a model in which the Akaike Information Criterion (AIC) is minimized using the stepwise method, and is a multiple regression equation with the enclosed air rate and LogKsat, as well as the sand content (%) and clay content (%) as variables.

[0037] As shown in FIG. 6(a), for "StepwiseAIC", R2 is maximized, but in simple regression, "root-encapsulated air" is larger than "LogKsat". As shown in Fig. 6(b), R is lower than in Fig. 6(a), but it can be applied to soil A shallower than 30 cm deep. 2 Although it is lower, it can be applied to soil A shallower than 30 cm deep. Even when applied to soil A shallower than 30 cm deep, in simple regression, R is such that "root-encapsulated air" is larger than "LogKsat", and in multiple regression, R is such that "root-encapsulated air * LogKsat" is the largest. 2 In simple regression, R is such that "root-encapsulated air" is larger than "LogKsat", and in multiple regression, R is such that "root-encapsulated air * LogKsat" is the largest. 2 In multiple regression, R is such that "root-encapsulated air * LogKsat" is the largest.

Industrial Applicability

[0038] According to the present invention, in a case where soil is carried in from the outside for imported soil, such as in a field where asparagus is cultivated in the open field or in a greenhouse using a framed raised-bed cultivation system, soil diagnosis for irrigation management can be performed on the carried-in soil, irrigation control suitable for this soil can be performed, and the soil can be maintained in the most appropriate moist state.

Explanation of Symbols

[0039] 1 pF value detection sensor 2 Irrigation device 3 Operating means 10 Irrigation control device 11 Control unit 12 Output unit 13 Storage unit A Soil

Claims

1. A soil diagnosis method for irrigation management, comprising: a soil moisture characteristic measurement step of measuring soil moisture for an undisturbed sample soil collected from the soil for which the irrigation management is to be performed, or for the undisturbed sample soil and a disturbed sample soil collected from the soil; a soil evaluation pF value determination step of determining, as a soil evaluation pF value, a pF value corresponding to a set WFPS value from the measurement values obtained in the soil moisture characteristic measurement step; a soil diagnosis step of diagnosing the soil based on the soil evaluation pF value determined in the soil evaluation pF value determination step ; In the soil diagnosis step, if the soil evaluation pF value is within a first set range, the soil is determined to be an appropriate soil for retaining water; if the soil evaluation pF value exceeds the first set range, the soil is determined to be an inappropriate soil for which there is concern about water absorption stress when attempting to optimize oxygen supply . A soil diagnosis method characterized by the above.

2. In the soil moisture characteristic measurement step, for the undisturbed sample soil, the relationship between the pF value and the volumetric water content is measured, a first soil moisture characteristic curve calculation step of calculating a pF value - volumetric water content curve from the measurement values obtained in the soil moisture characteristic measurement step; a WFPS calculation step of calculating WFPS from the measured volumetric water content and the porosity of the undisturbed sample soil; a second soil moisture characteristic curve calculation step of calculating a pF value - WFPS curve from the pF value - volumetric water content curve calculated in the first soil moisture characteristic curve calculation step and the WFPS calculated in the WFPS calculation step ; In the soil evaluation pF value determination step, the soil evaluation pF value is determined using the pF value - WFPS curve calculated in the second soil moisture characteristic curve calculation step. The soil diagnosis method according to claim 1, characterized by the above.

3. In the soil moisture characteristic measurement step, for the undisturbed sample soil, the volumetric water content and dry density at capillary saturation are calculated from the water content weight measured at capillary saturation and the dry weight measured after drying, and for the disturbed sample soil, the true specific gravity is calculated by the pycnometer method. An enclosed air rate calculation step of calculating the enclosed air rate using the volumetric water content, dry density, and true specific gravity at capillary saturation calculated in the soil moisture characteristic measurement step ; In the soil evaluation pF value determination step, the square root conversion value of the enclosed air rate calculated in the enclosed air rate calculation step is used as the root enclosed air rate to determine the soil evaluation pF value. a + b × square root of the entrapped air ratio (where a and b are coefficients) is determined by the formula The soil diagnosis method according to claim 1, characterized in that.

4. In the soil moisture characteristic measurement step, for the undisturbed sample soil, the saturated hydraulic conductivity is calculated by a saturated permeability test, In the soil evaluation pF value determination step, taking the common logarithm value of the saturated hydraulic conductivity calculated in the soil moisture characteristic measurement step as LogKsat, the soil evaluation pF value is a + c × LogKsat (where a and c are coefficients) is determined by the formula The soil diagnosis method according to claim 1, characterized in that.

5. In the soil moisture characteristic measurement step, for the undisturbed sample soil, from the water content weight measured after capillary saturation and the dry weight measured after drying, the volumetric water content and dry density at the time of capillary saturation are calculated, and the saturated hydraulic conductivity is calculated by a saturated permeability test. For the disturbed sample soil, the true specific gravity is calculated by the pycnometer method, An entrapped air ratio calculation step of calculating the entrapped air ratio using the volumetric water content, the dry density, and the true specific gravity at the time of capillary saturation calculated in the soil moisture characteristic measurement step is provided, In the soil evaluation pF value determination step, taking the square root conversion value of the entrapped air ratio calculated in the entrapped air ratio calculation step as the square root of the entrapped air ratio, and taking the common logarithm value of the saturated hydraulic conductivity calculated in the soil moisture characteristic measurement step as LogKsat, the soil evaluation pF value is a + b × square root of the entrapped air ratio + c × LogKsat + d × square root of the entrapped air ratio × LogKsat (where a, b, c, and d are coefficients) is determined by the formula The soil diagnosis method according to claim 1, characterized in that.

6. In the soil diagnosis step, if the soil evaluation pF value is below the first set range, it is determined that the soil is a soil that is difficult to retain moisture and requires small amount and frequent irrigation The soil diagnosis method according to any one of claims 1 to 5, characterized in that.

7. A irrigation control method using the soil evaluation pF value determined by the soil diagnosis method according to any one of claims 1 to 5, using the soil evaluation pF value as a monitored value, installing a pF value detection sensor in the soil from which the undisturbed sample soil was collected, starting irrigation when the detected pF value detected by the pF value detection sensor reaches the monitored value The irrigation control method, characterized in that.

8. An irrigation control device for performing the irrigation control method according to claim 7, Compare the detected pF value with the monitoring value, and when the detected pF value reaches the monitoring value, cause the irrigation device to start irrigation. An irrigation control device characterized by the above.

9. An irrigation control device that compares a detected pF value detected by a pF value detection sensor installed in the soil with a preset monitoring value, and when the detected pF value reaches the monitoring value, causes the irrigation device to start irrigation, using a soil evaluation pF value as the monitoring value, defining the soil evaluation pF value as the pF value corresponding to the set WFPS value of WFPS in the pF value - WFPS curve, wherein the pF value - WFPS curve is calculated from the pF value - volumetric water content curve based on the measured values of the undisturbed sample soil collected from the soil, and the WFPS based on the volumetric water content and porosity of the undisturbed sample soil. An irrigation control device characterized by the above.

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