AU2021101641A4

AU2021101641A4 - A Method for measuring soil bulk density

Info

Publication number: AU2021101641A4
Application number: AU2021101641A
Authority: AU
Inventors: Qiang CHAI; Zhuzhu Luo; Yining Niu
Original assignee: Gansu Agricultural University
Current assignee: Gansu Agricultural University
Priority date: 2021-03-30
Filing date: 2021-03-30
Publication date: 2021-05-27
Anticipated expiration: 2029-03-30

Abstract

The invention relates to method for measuring soil bulk density. The method for measuring soil bulk density comprises the following steps: filling a container whose mass and volume is known with fine particles, making it flush with the upper edge of the container, weighing and calculating the bulk density p of the fine particles; removing stone and residues from the surface of the soil whose bulk density needs to be measured, collecting the excavated soil after digging a hole on the ground, filling the hole with small particles from the container, making the particles in the hole flush with the edge of ground surface, weighing and recording the mass of the remaining fine particles in the container. Drying the collected soil to its constant weight, and weighing to obtain the mass of dry soil. Calculating the volume of the soil taken, and then the bulk density of the soil to be measured. This invention provides a solution to the problem of volume calculation of the soil sample commonly existing in the prior art, and it can obtain high measurement accuracy of bulk density of the soil sample.

Description

A Method for measuring soil bulk density

TECHNICAL FIELD This invention relates to a method for measuring soil bulk density

BACKGROUND In scientific research or production practice, it is usually necessary to measure soil bulk density to evaluate the impact of agricultural measures, such as crop system and farming methods, on soil physical properties. Bulk density is an important index to evaluate soil quality. The bulk density of soil indicates the compactness of soil, and the greater the bulk density, the greater the compactness of soil. Soil bulk density refers to the dry soil mass of undisturbed soil per unit volume, which indicates the mass of this substance per unit volume, and the unit is g/cm 3 or kg/M 3 . The undisturbed soil is the soil which is not disturbed by compression or expansion, and which contains air, water, plant roots and so on. In daily determination, the core method is usually used for determination. Generally, a solid ring with known volume is inserted into the soil with a small hammer, and then digging the ring out with soil attached to its surface, transporting back to the laboratory and carefully scraped the excess soil at both ends of the ring with a small knife. The soil off the ring is dried to constant weight at 105°C and weighed. Then, according to the volume of the ring and the mass of the soil, calculating the bulk density of the soil. To measure the bulk density of soil, it is usually necessary to measure two parameters of soil mass and volume, and keep the original state of soil. It is easy to measure the mass of soil, but it is difficult to measure the volume of soil. In order not to change the volume of soil, the soil should not be disturbed and compressed in the process of obtaining soil samples, otherwise it would change the shape of soil, and then would affect the determination of soil volume. At the same time, due to the influence of the surrounding environment, the sampling process is troublesome and there are many working procedures.

Chinese invention patent application 201610908725X discloses a classical method for measuring soil bulk density in the prior art. The tools required in this method are soil drill, solid ring and soil knife, and the specific method includes the following steps: (1) Ring positioning. Choosing a good test plot, putting the solid ring in the front section of the positioning rod, hitting the top end of the positioning rod with a hammer, and embedding the ring vertically into the soil. The front end of the positioning rod is a magnetic substance which can absorb the ring. (2) Recycling the ring, rotating the soil drill so that the ring cutter embedded in the soil and the surrounding soil are collected into the soil drill together, and then use the soil to remove the ring cutter from the soil drill. (3) Soil sample treatment, scraping the front and rear ends of the ring flat with a soil knife, carefully place the soil sample in an aluminum box, and bring it back to the laboratory for drying and weighing to calculate the soil bulk density. In this method, the soil bulk density can be quickly determined by the combination of soil sampling drill and ring cutter without damaging (or with little damage) the sample plot. Chinese invention patent application 2012102069479 discloses a method for measuring soil bulk density, which specifically comprises the following steps: collecting soil, putting the soil into a self-sealing bag, exhausting the air inside and sealing the self sealing bag when negative pressure exists in the sealed bag. Measuring the volume of the sealed self-sealing bag and the soil in it. Taking another empty self-sealing bag with the same specification as the above-mentioned self-sealing bag for holding soil, removing the air from it, seal it, and then measuring its volume. Sealing the soil in the bag, and drying it to constant weight to obtain the soil weight. Then calculating the soil bulk density according to the formula. The method provided by the invention can effectively reduce the error of measuring the volume of irregularly shaped soil, thereby improving the testing accuracy of soil bulk density. The method is suitable for measuring soil bulk density under special environment (complex environment and broken soil), especially for measuring soil bulk density on soil with discontinuous soil, more stones and plant roots in soil, thin soil layer or loose soil structure. The application of the two prior arts above does not solve the problem of measuring the volume of soil taken in practice.

Therefore, it is very necessary and important to find a simple and rapid method for measuring soil bulk density.

SUMMARY The invention provides a method for measuring the bulk density of soil, which can overcome the common defects in the prior art. A Method for measuring soil bulk density is characterized in that prepare fine particles with uniform texture and a container with mass m and volume vi in advance. The measurement steps are as follows: (1) Fill the container with fine particles and make it flush with the upper edge of the container, weighing and recording the total mass of the particles and container as m1, (2) Calculate the bulk density p of fine particles in step (1) according to formula (1),

p = (M1i - m)/v 1)@;

(3) Take sample from the soil to be measured: removing stone and residues from

the surface of the soil whose bulk density needs to be measured, dig a pit in the soil, collecting the excavated soil, the position of the pit is determined by the soil layer to be measured, and the soil taken out should not exceed the volume of the container (4) Filling the pit dug in step (3) with fine particles from the container, making the surface of the particles flush with the ground edge, weighing and recording the remaining fine particles in the container and the total mass of the container asm2 (5) Drying the soil collected in step (3) at 1050C in oven until the soil has a constant weight, and weighing to obtain the mass m3 of dry soil. (6) Calculating the volume v2 of the soil taken out in step (3) according to formula (2),

V2 = (m1 -mz )/p@

(7) Calculating the soil bulk density (BD) using formula@

BD = m3 /v 2 @

The container used in the present invention is preferably made of a material with little thermal deformation, and the fine particles used in the present invention can be fine metal particles, gravel, or any other granular materials.

Preferably, in the method for measuring soil bulk density of the present invention, the container is a glass container. The container used in the invention is made of glass material with small thermal deformation, which can make the measurement more accurate. Preferably, in the method for measuring soil bulk density of the present invention, the particle size of the fine particles is 20-40 meshes. The preferred fine particles in the present invention are suggested as gravel. According to the method, the volume problem of the taken soil sample which is common in the prior art can be satisfactorily solved, and the bulk density of the taken soil with high measurement accuracy can be measured.

DESCRIPTION OF THE INVENTION The invention will be explained with examples. In this embodiment, the particles used are quartz sand with a particle size of 20-40 meshes, and the container used is a glass with a volume of 326ml and a mass of 110 grams. The measurement method of this example is as follows: Choosing 20-40 mesh laboratory quartz sand and put it in a glass with a volume of 326ml. The mass of the glass is 11Og, and the mass of the glass filled with quartz sand is 565.65g(mi). According to formula @, the density of quartz sand is calculated to be 1.398 g/cm3 (the bulk density of quartz sand). Taking soil sample according to the soil sampling procedure. Digging a small hole after removing residues from the soil surface where the soil bulk density needs to be measured, and carefully packing the excavated soil into a marked sampling bag (if the water content needs to be measured, the soil sample can be packaged in a plastic bag first). The position and depth of the hole are determined according to the soil level to be measured. When taking soil, ensuring not to make the amount of soil exceeds the volume of the container (glass). In this embodiment, putting the soil taken out, into a paper bag, and then taking a glass filled with quartz sand, and the quartz sand is poured into the soil pit, so that the sand is flush with the upper edge of the soil pit. The mass of the remaining sand and glass is 470.87g (including the mass of glass), so the net mass of sand in the soil pit is 94.78g; Using formula @, the volume of sand is calculated to be 67.80 cubic centimeters, which is equal to the volume of soil taken out. The soil samples brought back to the laboratory are dried in an oven at 1050 C until reaching its constant weight. Weighing the dry soil mass is 81.22g. Using formula (3), the bulk density of soil is 3 calculated to be 1.20g/cm

.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: 1. A Method for measuring soil bulk density is characterized in that prepare fine particles with uniform texture and a container with mass m and volume vi in advance. The measurement steps are as follows: (1) Fill the container with fine particles and make it flush with the upper edge of the container, weighing and recording the total mass of the particles and container as m1, (2) Calculate the bulk density p of fine particles in step (1) according to formula (1),

p = (M1i - m)/v 1)@;

(3) Take sample from the soil to be measured: removing impurities from the

surface of the soil whose bulk density needs to be measured, dig a pit in the soil, collecting the excavated soil, the position of the pit is determined by the soil layer to be measured, and the soil taken should not exceed the volume of the container (4) Filling the pit dug in step (3) with fine particles from the container, making the surface of the particles flush with the ground edge, weighing and recording the remaining fine particles in the container and the total mass of the container as m 2

(5) Drying the soil collected in step (3) at 1050 C until the soil has a constant weight, and weighing to obtain the mass m 3 of dry soil. (6) Calculating the volume v2 of the soil taken out in step (3) according to formula (2),

V2 = (M1 - 2)/p@

(7) Calculating the bulk density BD of the soil to be measured by using formula@

BD = m3 /v 2 @
2. A Method for measuring soil bulk density, according to claim 1, is characterized in that

the container described is made of glass
3. A Method for measuring soil bulk density, according to claim 1, is characterized in that the size of the fine particles is 20-40 meshes.
4. A Method for measuring soil bulk density, according to claim 1, is characterized in that the fine particles described are gavels.