CN104331639A - Indirect soil moisture content obtaining and rapid evaluation method - Google Patents

Abstract

The invention discloses an indirect soil moisture content obtaining and rapid evaluation. The method sequentially comprises the following steps: 1. designing a sampling scheme based on a research region; 2. sampling each sampling point by using a cutting-ring method and measuring soil bulk density, soil moisture content and soil compaction degree; 3. carrying out nucleoid simulation on data by using models to obtain coefficients of the different models and correlation coefficients; and determining an application model of the research region; 4. carrying out a soil compaction degree test on each sampling point and substituting the obtained data into the application model to obtain a result of the soil moisture content; and 5. carrying out whole calculation on the soil moisture content by using an area weighting average value method to rapidly evaluate the soil moisture content of the research region. According to the implementation scheme, an ordered system is achieved and the obtaining speed is rapid; the quantity of samples is more and the uncertainty caused by heterogeneity of soil spaces can be effectively reduced; and the indirect soil moisture content obtaining and rapid evaluation method can be applied to regions which are covered with different crops and have different soil textures and landforms.

Description

A kind of soil moisture content obtains and fast appraisement method indirectly

Technical field

The present invention relates to a kind of soil moisture content indirectly to obtain and fast appraisement method, be applicable to reclamation engineering of land and farmland water conservancy works field to soil moisture content long term monitoring and Fast Evaluation.

Background technology

Soil moisture content is the important parameter characterizing soil characteristic and agricultural production situation, all plays conclusive effect for " four water " conversion and cycle, geotechnical property, crop and root growth, crop yield.Measure and the research of acquisition methods soil moisture content, be the focus that researcher is concerned about always, if application for a patent for invention number is 201310643783.0 disclosed " colorimetric estimation methods of soil moisture content "; Application for a patent for invention number is 201310584218.1 disclosed " a kind of bobbin formula soil moisture content detection method based on frequency domain reflectometry and devices "; Application for a patent for invention number is 201310398355.6 disclosed " a kind of soil moisture content distributed measurement method and system ".Although it is that soil moisture content is measured and acquisition methods that above-mentioned patent all relates to, slower to soil moisture content acquisition speed; And due to tool count quantitative limitation, sampling spot is on the low side, the special heterogeneity of soil is finally caused to affect very large.

The acquisition methods of soil moisture content is a lot, and the most frequently used method mainly contains weight method, tensiometer method and time domain reflectometry etc.Weight method also claims oven drying method, directly can measure soil moisture content, although measuring accuracy is high, cost is higher, ageing poor.It is fast that tensiometer method and time domain reflectometry all have measuring speed, easy and simple to handle, degree of accuracy advantages of higher, but in space large scale when instrument restricted number, can consider not enough to soil space heterogeneity.The fast development of China's reclamation engineering of land and irrigation and water conservancy production and scientific research, need a kind of quick obtaining and evaluation method of soil moisture content of Field Scale, understand soil moisture content and soil moisture content in time, thus provide support data in time and accurately for guiding agricultural production and water-saving irrigation.

Soil density, also known as soil cone index or soil penetration resistance, is by Soil Anti shearing, and the overall target of the resistance of soil that force of compression and friction force etc. are formed is the important parameter in soil texture.Soil density is to soil water movement, and the g and D of crop root, the utilization factor of chemical fertilizer etc. have important impact, may be used for evaluating and characterizing soil characteristic.Soil density is mainly subject to soil types, the various factors such as unit weight and water percentage.Now there are some researches show, there is certain funtcional relationship in soil density and above-mentioned three factors.At present, soil density Simulation and Prediction model mainly contains Ayers model, Upadhyaya model, Busscher model and Hernanz model etc.

Surveying instrument soil density instrument due to soil density can carry out the continuous field monitoring of room and time to the soil layer of different depth, have operation simple and easy, little to the destructiveness of soil, accuracy and the advantage such as ageing.Therefore, the indirect determination of soil moisture content can be carried out based on soil compaction instrument.

Summary of the invention

Technical matters: the object of the invention is to overcome the deficiencies in the prior art part, provides the soil moisture content that a kind of acquisition speed is fast, precision is higher, effective indirectly to obtain and fast appraisement method.

Technical scheme: for achieving the above object, soil moisture content of the present invention obtains and fast appraisement method indirectly, comprises the following steps:

Step 1, based on survey region, consider the soil texture, agrotype and topography and geomorphology, take equidistant sampling method, design sample scheme, arrange sampling spot; The area S of each sampling spot _i(i=1,2 ... N) be 3 ~ 5m ², number of samples N is 15 ~ 25;

Step 2, use core cutter method sample each sampling spot, use oven drying method to measure soil weight BD respectively to institute's sample thief _i(i=1,2 ... N) and soil moisture content θ _i(i=1,2 ... N); Use soil density instrument to the soil density CI of each sampling spot soil layer _i(i=1,2 ... N) repeatedly test and average;

Step 3, area S based on sampling spot _i, soil weight BD _i, soil moisture content θ _iwith soil density CI _i(i=1,2 ... N) data, utilize model:

Model 1:Ayers model

$\mathrm{CI}=(A_1\×{\mathrm{BD}}^{A_4})/(A_2+{(\mathrm{\θ}-A_3)}^2)---\left(1\right)$

Model 2:Upadhyaya model

$\mathrm{CI}=B_1{\mathrm{BD}}^{B_2}{e}^{-B_3\mathrm{\θ}}---\left(2\right)$

Model 3:Busscher model

$\mathrm{CI}=C_1{\mathrm{\θ}}^{C_2}{\mathrm{BD}}^{C_3}---\left(3\right)$

Model 4:Hernanz model

$\mathrm{CI}=D_1{\mathrm{\θ}}^{D_2}{\mathrm{BD}}^{D_3}{d}^{D_4}---\left(4\right)$

Carry out nucleoid, obtain coefficient to be determined and the related coefficient of selected model, the maximum model of related coefficient is defined as the application model of this survey region; In formula: CI is soil density, kPa; BD is the soil weight, g/cm ³; θ is soil quality water percentage; D is the degree of depth, mm; A, B, C, D are the fitting constant depending on soil types, and perseverance is just;

Step 4, use soil density instrument are to the soil density CI of each sampling spot soil layer _j(j=1,2 ... M) repeatedly test and average, by soil density CI _jsubstitute into application model, obtain soil moisture content θ _j(j=1,2 ... M);

Step 5, utilize the method for area weighted average, pass through formula;

θ＝Σθ _j×S _j/ΣS _j(5)

Overall calculation is carried out, with the soil moisture content in this evaluation study region to the soil moisture content θ of survey region.

The area S of described each sampling spot _iequal and opposite in direction or close to equal.

If the special heterogeneity of survey region is little, described soil weight BD _inumber of samples measure 3 ~ 5, utilize formula:

BD＝ΣBD _i×S _i/ΣS _i(6)

Obtain the mean value of the soil weight.

Constant airspeed value during described soil density instrument insertion soil is 30mm/s.

The soil density CI of described each sampling spot _iand CI _jthe number of times of repetitive measurement is taked to be 3-5 time.

Described method of carrying out nucleoid adopts the method based on principle of least square method, is realized by programming or origin software.

Described survey region area >120m ², and when the soil texture, crop species, topography and geomorphology difference are larger, the soil moisture content of assessing zonings survey region.

Described sampling depth is 10 ~ 20cm.

Beneficial effect: soil moisture content indirect determination of the present invention and evaluation method, by the acquisition to on-site sampling point degree of packing data, the soil moisture content data of quick obtaining regional scale are carried out based on mathematical model, embodiment system orderliness, acquisition speed is fast, less to the destructiveness of soil, quantity of sampling quantity is many, the uncertainty that soil space heterogeneity causes can be effectively reduced, can be applicable to Different Crop cover, the area of the soil texture and topography and geomorphology, solves soil moisture content and indirectly obtains the technical matters with Fast Evaluation.The present invention may be used for reclamation engineering of land and farmland water conservancy works field, result of calculation can realize visual based on ARCGIS, mark in each geographical grid by soil moisture content data with the form of landform, use different colors to characterize, can be used for the analysis of soil moisture content Characteristics of spatio-temporal.Its acquisition speed is fast, precision is higher, be conducive to agricultural management and scientific research personnel obtains soil moisture content and evaluates.

Accompanying drawing explanation

Fig. 1 is soil moisture content indirect determination of the present invention and evaluation method process flow diagram;

Fig. 2 is the arrangenent diagram of test site of the present invention;

Fig. 3 is experimental point of the present invention and Ayers model simulation results comparison diagram;

Fig. 4 is experimental point of the present invention and Upadhyaya model simulation results comparison diagram.

Embodiment

Below in conjunction with accompanying drawing, one embodiment of the present of invention are further described:

Soil moisture content of the present invention obtains and fast appraisement method indirectly, and concrete steps are as follows:

Step 1, based on survey region, consider the soil texture, agrotype and topography and geomorphology, take equidistant sampling method, design sample scheme, arrange sampling spot; The area S of each sampling spot _i(i=1,2 ... N) be 3 ~ 5m ², number of samples N is 15 ~ 25; The area S of described each sampling spot _iequal and opposite in direction or close to equal, sampling depth is 10 ~ 20cm.

Step 2, use core cutter method sample each sampling spot, use oven drying method to measure soil weight BD respectively to institute's sample thief _i(i=1,2 ... N) and soil moisture content θ _i(i=1,2 ... N); Use soil density instrument to the soil density CI of each sampling spot soil layer _i(i=1,2 ... N) repeatedly test and average; Constant airspeed value during described soil density instrument insertion soil is 30mm/s.

Step 3, area S based on sampling spot _i, soil weight BD _i, soil moisture content θ _iwith soil density CI _i(i=1,2 ... N) data, utilize model:

Model 1:Ayers model

$\mathrm{CI}=(A_1\×{\mathrm{BD}}^{A_4})/(A_2+{(\mathrm{\θ}-A_3)}^2)---\left(1\right)$

Model 2:Upadhyaya model

$\mathrm{CI}=B_1{\mathrm{BD}}^{B_2}{e}^{-B_3\mathrm{\θ}}---\left(2\right)$

Model 3:Busscher model

$\mathrm{CI}=C_1{\mathrm{\θ}}^{C_2}{\mathrm{BD}}^{C_3}---\left(3\right)$

Model 4:Hernanz model

$\mathrm{CI}=D_1{\mathrm{\θ}}^{D_2}{\mathrm{BD}}^{D_3}{d}^{D_4}---\left(4\right)$

Carry out nucleoid, the method employing carrying out nucleoid, based on the method for principle of least square method, is realized by programming or origin software; Obtain coefficient to be determined and the related coefficient of selected model, the maximum model of related coefficient is defined as the application model of this survey region; In formula: CI is soil density, kPa; BD is the soil weight, g/cm ³; θ is soil quality water percentage; D is the degree of depth, mm; A, B, C, D are the fitting constant depending on soil types, and perseverance is just; Described survey region area >120m ², and when the soil texture, crop species, topography and geomorphology difference are larger, the soil moisture content of assessing zonings survey region.

If the special heterogeneity of survey region is little, soil weight BD _inumber of samples measure 3 ~ 5, utilize formula:

BD＝ΣBD _i×S _i/ΣS _i(6)

Obtain the mean value of the soil weight.

Step 4, use soil density instrument are to the soil density CI of each sampling spot soil layer _j(j=1,2 ... M) repeatedly test and average, by soil density CI _jsubstitute into application model, obtain soil moisture content θ _j(j=1,2 ... M); The soil density CI of each sampling spot _iand CI _jthe number of times of repetitive measurement is taked to be 3-5 time.

Step 5, utilize the method for area weighted average, pass through formula;

θ＝Σθ _j×S _j/ΣS _j(5)

Overall calculation is carried out, with the soil moisture content in this evaluation study region to the soil moisture content θ of survey region.

Example 1: the Demonstration Base that the Loess Gullys restoration of the ecosystem choosing Shaanxi Province's Yulin City infrared ray light shine is built, chooses demonstration land used B district.This district's gradient is 4 °, and area is 8.77 mu, whole maize planting, and application rate is 1.5Kg/ mu.Experimental field B1, B2, B3, BC divide 4 kinds; Often kind of sample plot 3 sampling spots, Gong12Ge community.The arrangenent diagram of test site is shown in Fig. 2.This area average annual rainfall is about 380mm, focuses mostly on rainy season 7, August; Annual mean ground temperature is 2111.2mm.

6120 type pointer-type soil density instrument (measurement ranges: 0 ~ 600psi are selected in test, 1psi=6.89KPa), select 3/4 inch diameter nose cone, respectively on September 3rd, 2013, September 24, October 28, to 10 ~ 20cm soil layer of 12 sampling spots, has carried out the soil weight, the measurement of the degree of packing and water percentage.

The coefficient to be determined of the Ayers model that table 1 obtains for nucleoid and Upadhyaya model and related coefficient.Fig. 3 and 4 is the comparison diagram of two model simulation results and experiment value.As can be seen from Figure 3, there is flex point in the water percentage of Ayers modeling and the relation curve of soil density, and in the flex point left and right sides, water percentage and soil density are a kind of positive correlation and negative correlativing relation of dullness respectively.As can be seen from Figure 4, the water percentage of Upadhyaya modeling and soil density are a kind of negative correlativing relations of dullness.

From table 1 and Fig. 3,4 can find out, two models have all carried out good nucleoid to experimental data, and related coefficient is very high, can as the model of this survey region.Each experiment, is measured by the soil density of 12 sampling spots to survey region, obtains soil moisture content and the space distribution thereof of different sampling spot in time; And the soil moisture content of this survey region of the soil moisture content data overall evaluation can be utilized.

As can be seen from above-described embodiment, the present invention is by the acquisition to on-site sampling point degree of packing data, the soil moisture content data of quick obtaining regional scale are carried out based on mathematical model, less to the destructiveness of soil, quantity of sampling quantity is many, the impact of soil space heterogeneity can be effectively reduced, can be applicable to Different Crop and cover, the area of the soil texture and topography and geomorphology.

It should be pointed out that for engineering management and scientific research personnel, under the prerequisite not departing from the technology of the present invention principle, can make some improvement or distortion, these improve or distortion also should be considered as protection scope of the present invention.

The parameter to be determined of table 1 two models and related coefficient

Claims (8)

1. soil moisture content obtains and a fast appraisement method indirectly, it is characterized in that comprising the steps:

Step 1, based on survey region, consider the soil texture, agrotype and topography and geomorphology, take equidistant sampling method, design sample scheme, arrange sampling spot; The area S of each sampling spot _i(i=1,2 ... N) be 3 ~ 5m ², number of samples N is 15 ~ 25;

Step 2, use core cutter method sample each sampling spot, use oven drying method to measure soil weight BD respectively to institute's sample thief _i(i=1,2 ... N) and soil moisture content θ _i(i=1,2 ... N); Use soil density instrument to the soil density CI of each sampling spot soil layer _i(i=1,2 ... N) repeatedly test and average;

Step 3, area S based on sampling spot _i, soil weight BD _i, soil moisture content θ _iwith soil density CI _i(i=1,2 ... N) data, utilize model:

Model 1:Ayers model

$\mathrm{CI}=(A_1\×{\mathrm{BD}}^{A_4})/(A_2+{(\mathrm{\θ}-A_3)}^2)---\left(1\right)$

Model 2:Upadhyaya model

$\mathrm{CI}=B_1{\mathrm{BD}}^{B_2}{e}^{{-B}_3\mathrm{\θ}}---\left(2\right)$

Model 3:Busscher model

$\mathrm{CI}=C_1{\mathrm{\θ}}^{C_2}{\mathrm{BD}}^{C_3}---\left(3\right)$

Model 4:Hernanz model

$\mathrm{CI}=D_1{\mathrm{\θ}}^{D_2}{\mathrm{BD}}^{D_3}{d}^{D_4}---\left(4\right)$

Carry out nucleoid, obtain coefficient to be determined and the related coefficient of selected model, the maximum model of related coefficient is defined as the application model of this survey region; In formula: CI is soil density, kPa; BD is the soil weight, g/cm ³; θ is soil quality water percentage; D is the degree of depth, mm; A, B, C, D are the fitting constant depending on soil types, and perseverance is just;

Step 4, use soil density instrument are to the soil density CI of each sampling spot soil layer _j(j=1,2 ... M) repeatedly test and average, by soil density CI _jsubstitute into application model, obtain soil moisture content θ _j(j=1,2 ... M);

Step 5, utilize the method for area weighted average, pass through formula;

θ＝Σθ _j×S _j/ΣS _j(5)

Overall calculation is carried out, with the soil moisture content in this evaluation study region to the soil moisture content θ of survey region.

2. as right 1 require as described in a kind of soil moisture content indirectly obtain and fast appraisement method, it is characterized in that: the area S of described each sampling spot _iequal and opposite in direction or close to equal.

3. as right 1 require as described in a kind of soil moisture content indirectly obtain and fast appraisement method, it is characterized in that: if the special heterogeneity of survey region is little, described soil weight BD _inumber of samples measure 3 ~ 5, utilize formula:

BD＝ΣBD _i×S _i/ΣS _i(6)

Obtain the mean value of the soil weight.

4. as right 1 require as described in a kind of soil moisture content indirectly obtain and fast appraisement method, it is characterized in that: constant airspeed value when described soil density instrument inserts soil is 30mm/s.

5. as right 1 require as described in a kind of soil moisture content indirectly obtain and fast appraisement method, it is characterized in that: the soil density CI of described each sampling spot _iand CI _jthe number of times of repetitive measurement is taked to be 3-5 time.

6. as right 1 require as described in a kind of soil moisture content indirectly obtain and fast appraisement method, it is characterized in that: described in carry out nucleoid method adopt based on the method for principle of least square method, realized by programming or origin software.

7. as right 1 require as described in a kind of soil moisture content indirectly obtain and fast appraisement method, it is characterized in that: described survey region area >120m ², and when the soil texture, crop species, topography and geomorphology difference are larger, the soil moisture content of assessing zonings survey region.

8. as right 1 require as described in a kind of soil moisture content indirectly obtain and fast appraisement method, it is characterized in that: described sampling depth is 10 ~ 20cm.