CN104198317A - Method for measuring physical parameter S of soil - Google Patents

Abstract

The invention discloses a method for measuring a physical parameter S of soil, relating to a method for solving a performance parameter, and aiming at solving the problems that measurement instruments are expensive and measurement periods are long as the measurement of the physical mass parameter S of the soil depends on a van Genuchten equation of a water soil water characteristic curve. The method comprises the following steps: step one, sieving an air-dried soil sample by virtue of a 2-mm sieve and dividing the soil sample into two parts; step two, measuring a saturation moisture content theta s and a field moisture capacity theta (fc) by using the first part of the soil sample; step three, measuring a residual moisture content theta r by using the second part of the soil sample; step four, obtaining a parameter n according to a formula as shown in the specification; and step five, obtaining the physical parameter S of the soil according to another formula as shown in the specification.

Description

Measure the method for soil physical parameters S

Technical field

The present invention relates to a kind of method for solving of performance parameter, belong to soil characteristic research field.

Background technology

The traditional parameters that represents soil physical properties quality mainly comprises the indexs such as hole character, structural, unit weight, Moisture Availability, characteristic curve of soil moisture, harmomegathus, glutinous grain dispersion degree.But these indexs only can reflect soil physical property in a certain respect, the comprehensively Comprehensive Traits of reflect soil physical property.Soil physics mass parameter S refers to the slope of characteristic curve of soil moisture when flex point.S not only can fully demonstrate soil in the feature of the aspects such as moisture conduction, degree of tightness situation, tilth, Moisture Availability, mechanical resistance, the influence degree that effectively reflect soil physical property is grown plant root growth.According to the value of S, soil physics quality is divided can be divided into fabulous (S >=0.050), good (0.050>S >=0.035), poor (0.035>S >=0.020) and four grades of extreme difference (S<0.020).At present, use S as judgement and represent that the parameter index of soil physics quality character is generally accepted in the world.

The computing formula of soil physics mass parameter S is:

$S=n\&times;({\mathrm{\&theta;}}_s-{\mathrm{\&theta;}}_r){\left[\frac{2n-1}{n-1}\right]}^{[\frac{1}{n}-2]}$

In formula, θ _sand θ _rbe respectively saturation moisture content and residual water content, kg kg ^-1; N is characteristic curve of soil moisture van Genuchten model θ=(θ _s-θ _r) [1+ (α h) ⁿ] ^-m+ θ _rin parameter, in this model formation, θ is soil moisture content, kg kg ^-1, h is soil water suction, hPa (cm); α, m, n are soil moisture parameter of curve, and have relational expression m=1 – 1/n.

At present, the mensuration of soil physics mass parameter S is conventionally first measured after characteristic curve of soil moisture van Genuchten equation obtains its parameter n and according to aforementioned formula, is obtained S again.And characteristic curve of soil moisture van Genuchten equation adopts measurement method to obtain conventionally, by methods such as pressure membrane instrument, supercentrifuge, plane type instruments, measure the different water suction force values of soil and corresponding soil moisture content thereof, then by mathematical software fit equation.The main weak point of the method is consuming time very long, according to the difference of soil types, conventionally needs the time that one month to several months do not wait; In addition, the instrument that the method needs is very expensive, as pressure membrane instrument, supercentrifuge price tens0000 to hundreds of thousands not etc., plane type instrument will be several ten thousand yuan of left and right, common pedology laboratory seldom can be equipped with these instruments.

Summary of the invention

The present invention seeks to depend on characteristic curve of soil moisture van Genuchten equation in order to solve the mensuration of soil physics mass parameter S, have the problem that surveying instrument is expensive, measuring period is long, a kind of method of measuring soil physical parameters S is provided.

The method of mensuration soil physical parameters S of the present invention, the method comprises the following steps:

Step 1, the soil sample after air-dry is crossed to 2mm sieve, and be divided into two parts;

Step 2, utilize first part of soil sample to measure saturation moisture content θ _swith field capacity θ _fc;

Step 3, utilize second part of soil sample to measure residual water content θ _r;

Step 4, according to formula

$n=\frac{1}{1-56.17\exp [-8.141\frac{{\mathrm{\&theta;}}_{\mathrm{fc}}-{\mathrm{\&theta;}}_r}{{\mathrm{\&theta;}}_s-{\mathrm{\&theta;}}_r}]}$

N gets parms;

Step 5, according to formula

$S=n\&times;({\mathrm{\&theta;}}_s-{\mathrm{\&theta;}}_r){\left[\frac{2n-1}{n-1}\right]}^{[\frac{1}{n}-2]}$

Obtain soil physical parameters S.

Advantage of the present invention: the present invention adopts the experimental facilities of cheap and simple, measures water-retaining quantity among field of soil (θ at short notice _fc) and θ _s, θ _r, then by the method for mathematical computations, determine parameter n, and then try to achieve S value, adopt technical scheme of the present invention, measuring S value only needs just can complete for 2 days, has reached the object that shortens experimental period.

Accompanying drawing explanation

Fig. 1 is the process flow diagram of the method for mensuration soil physical parameters S of the present invention.

Embodiment

Embodiment one: below in conjunction with Fig. 1, present embodiment is described, measures the method for soil physical parameters S described in present embodiment, the method comprises the following steps:

Step 1, the soil sample after air-dry is crossed to 2mm sieve, and be divided into two parts;

Step 2, utilize first part of soil sample to measure saturation moisture content θ _swith field capacity θ _fc;

Step 3, utilize second part of soil sample to measure residual water content θ _r;

Step 4, according to formula

$n=\frac{1}{1-56.17\exp [-8.141\frac{{\mathrm{\&theta;}}_{\mathrm{fc}}-{\mathrm{\&theta;}}_r}{{\mathrm{\&theta;}}_s-{\mathrm{\&theta;}}_r}]}$

N gets parms;

Step 5, according to formula

$S=n\&times;({\mathrm{\&theta;}}_s-{\mathrm{\&theta;}}_r){\left[\frac{2n-1}{n-1}\right]}^{[\frac{1}{n}-2]}$

Obtain soil physical parameters S.

The first part of soil sample of utilizing in step 2 measured saturation moisture content θ _swith field capacity θ _fcprocess be:

Packing first part of soil sample into quality is w ₁cutting ring in, build the upper and lower port lid of this cutting ring, use scales/electronic balance weighing is w ₂; Be put in the enamel tray being filled with water, down, in enamel tray, the water surface, compared with the low 1-2 millimeter in port lid edge on cutting ring, does not make waterflooding above cutting ring in lower port lid one end.Allow water saturation soil 20 hours～24 hours; The cutting ring of soil sample is equipped with in taking-up, dries cutting ring outer wall moisture, is weighed as w ₃; Open lower port lid and expose the filter paper in it, cutting ring is placed on sand table together with filter paper, after sand table water suction in 8 hours, take down port lid on cutting ring, in cutting ring, take out 15-20 gram of soil sample, put into known weight w ₄aluminium box in, be weighed as w ₅, then put into baking oven and dry to constant weight at 105 ℃, then be weighed as w ₆;

Adopt formula obtain saturation moisture content θ _s;

Adopt formula obtain field capacity θ _fc.

The second part of soil sample of utilizing in step 3 measured residual water content θ _rprocess be: adopt classical oven drying method to measure the water cut of second part of soil sample, and as residual water content θ _r.

It is centesimal electronic balance that electronic balance is selected precision.

Instrument and price that present embodiment adopts are as shown in table 1.

Instrument and price that table 1 adopts

Instrument is simple, price is very cheap.

Embodiment two: present embodiment provides a specific embodiment, soil sample adopts sandy soil, the master data θ that application the inventive method is measured _s=0.2436kg kg ^-1; θ _r=0.00kg kg ^-1; θ _fc=0.1424kg kg ^-1, the n=1.929 that the inventive method calculates, the S=0.0889 that the inventive method calculates, the S=0.0894 that adopts traditional measurement method to measure, relative error is 0.56%, relative error is very little.

Embodiment three: present embodiment provides a specific embodiment, soil sample adopts loam, the master data θ that application the inventive method is measured _s=0.3646kg kg ^-1; θ _r=0.0897kg kg ^-1; θ _fc=0.2576kg kg ^-1, the n=1.6370 that the inventive method calculates, the S=0.0768 that the inventive method calculates, the S=0.0777 that adopts traditional measurement method to measure, relative error is 1.16%, relative error is very little.

Embodiment four: present embodiment provides a specific embodiment, soil sample adopts clay, the master data θ that application the inventive method is measured _s=0.4864kg kg ^-1; θ _r=0.1206kg kg ^-1; θ _fc=0.3586kg kg ^-1, the n=1.3914 that the inventive method calculates, the S=0.0729 that the inventive method calculates, the S=0.0718 that adopts traditional measurement method to measure, relative error is 1.53%, relative error is very little.

Claims (4)

1. measure the method for soil physical parameters S, it is characterized in that, the method comprises the following steps:

Step 1, the soil sample after air-dry is crossed to 2mm sieve, and be divided into two parts;

Step 2, utilize first part of soil sample to measure saturation moisture content θ _swith field capacity θ _fc;

Step 3, utilize second part of soil sample to measure residual water content θ _r;

Step 4, according to formula

$n=\frac{1}{1-56.17\exp [-8.141\frac{{\mathrm{\&theta;}}_{\mathrm{fc}}-{\mathrm{\&theta;}}_r}{{\mathrm{\&theta;}}_s-{\mathrm{\&theta;}}_r}]}$

N gets parms;

Step 5, according to formula

$S=n\&times;({\mathrm{\&theta;}}_s-{\mathrm{\&theta;}}_r){\left[\frac{2n-1}{n-1}\right]}^{[\frac{1}{n}-2]}$

Obtain soil physical parameters S.

2. measure according to claim 1 the method for soil physical parameters S, it is characterized in that, the first part of soil sample of utilizing in step 2 measured saturation moisture content θ _swith field capacity θ _fcprocess be:

Packing first part of soil sample into quality is w ₁cutting ring in, build the upper and lower port lid of this cutting ring, use scales/electronic balance weighing is w ₂; Be put in the enamel tray being filled with water, down, the water surface, compared with the low 1-2 millimeter in port lid edge on cutting ring, allows water saturation soil 20 hours～24 hours in enamel tray in lower port lid one end; The cutting ring of soil sample is equipped with in taking-up, dries cutting ring outer wall moisture, is weighed as w ₃; Open lower port lid and expose the filter paper in it, cutting ring is placed on sand table together with filter paper, after sand table water suction in 8 hours, take down port lid on cutting ring, in cutting ring, take out 15-20 gram of soil sample, put into known weight w ₄aluminium box in, be weighed as w ₅, then put into baking oven and dry to constant weight at 105 ℃, then be weighed as w ₆;

Adopt formula obtain saturation moisture content θ _s;

Adopt formula obtain field capacity θ _fc.

3. measure according to claim 1 the method for soil physical parameters S, it is characterized in that, the second part of soil sample of utilizing in step 3 measured residual water content θ _rprocess be: adopt classical oven drying method to measure the water cut of second part of soil sample, and as residual water content θ _r.

4. measure according to claim 2 the method for soil physical parameters S, it is characterized in that, it is centesimal electronic balance that electronic balance is selected precision.