The Soil Physics Laboratory

Soil samples can be brought or sent to us as loose soil or as undisturbed soil samples, depending on what analyses should be performed. Short descriptions of the methods we use are listed below.

Loose soil in bags, cups, boxes, containers etc

For many of the analyses the original soil sample is first air-dried, grinded and sieved at 2 mm mesh to get the “prepared fine soil sample”.

Soil particle size distribution

The particle size distribution in a soil sample is determined with different methods as related to fraction size. The content of particles larger than 2 mm are determined in the fine soil preparation by dry sieving of the air-dried, grinded sample. For determining the content of particles smaller than 2 mm, a combination of wet sieving (0.06-2 mm) and pipette method (<0.2 mm) is performed with the prepared fine soil. The fractions that can be obtained are: Coarse sand (0.6-2 mm), Medium sand (0.2-0.6 mm), Fine sand (0.06-0.2 mm), Coarse silt (0.02-0.06 mm), Medium silt (0.006-0.02 mm), Fine silt (0.002-0.006 mm) and Clay (< 0.002 mm).

We also have the recent method of integral suspension pressure (ISP) from METER called PARIO. PARIO automatically measures pressure and temperature in a suspension of soil particles , using Stokes law to estimate  particle sizes. This data is combined in the program with the sand content obtained from the wet sieving. The program estimates  the content of the clay (<0.002 mm), fine silt (0.002-0.0063 mm), middle silt (0.0063-0.02 mm), coarse silt (0.02-0.063 mm), fine sand (0.063—0.2 mm), middle sand (0.2-0.63 mm) and coarse sand (0.63-2 mm).

Furthermore, particle sizes in the range from 2 mm to 0.000010 mm (10 nm) can be determined with laser scattering particle size distribution analyzer (partica LA-950 V2 from HORIBA). This analysis is carried out in solvent (water) that allows for measuring dry (soil) and wet (water) samples.

Gravimetric soil water content

Original soil sample is weighed, oven-dried overnight at 105° C and then weighed again. The water content is then calculated from weight before and after oven-drying (percentage by weight).

Loss in ignition and organic matter content

Prepared fine soil sample is oven-dried overnight at 105°C to get rid of water. The sample is subsequently oven-dried at 550°C for 4 hours to get the loss on ignition. The organic matter content is approximated from the loss on ignition with a reduction factor related to clay content.

Wilting point

Prepared fine soil sample is wetted and placed in a pressure plate extractor at 1500 kPa to get the water content remaining at -1500 kPa soil water pressure.

Particle density

Particle density is calculated from the volume displacement of prepared fine soil sample in a flask with ethanol.

Soil core samples in cylinders

At the Soil Physics Laboratory we use cylinders with 5 or 10 cm height, 7.5 cm outer diameter, and 7.2 cm inner diameter to analyze the soil core properties.

Water retention properties

Water retention properties are measured by placing soil cylinder samples in sandbox (-0.05 to -10 kPa), on suction plate (-10 to -60 kPa), and in pressure plate extractor (-60 kPa to -100 kPa) and then oven dried to calculate the water content and dry bulk density in the soils.

The last step for the water retention curve is the wilting point in pressure plate extractor (-1500 kPa) using prepared fine soil sample.

Actual field soil water content and dry bulk density

Field water content (percentage by volume) and dry bulk density are obtained by oven-drying the soil cylinder samples at 105°C during 3 days, and base calculations on weight before and after drying and cylinder or soil core volume.

Porosity

Porosity is calculated from dry bulk density and particle density values.

Saturated hydraulic conductivity 

Saturated hydraulic conductivity is estimated by means of a constant head permeameter. Water passes through the water saturated soil cylinder sample at a constant water head, and it is collected in a graduated cylinder at the outlet of the sample. The saturated hydraulic conductivity is then calculated from water head, soil sample length, water temperature and outflow velocity.

Shrinkage

The actual volume of the core sample after drying in the oven at 105°C is measured, and compared with the original cylinder volume.

Soil cylinders

Soil cylinders with exact volume. Otherwise preparation is required (trim and/or measuring actual volume).

** It is necessary to provide soil cylinders, but also loose soil for the particle density calculations.

Loose soil (in bags, cups, boxes, containers, etc)

Soil that has been air dried (<5% water content, max. temp. 35°C) and sieved at 2 mm. Fresh soil requires preparation.

General information to provide

This information is required in the form to fill before delivering the soil samples:

Contact person (the responsible person of the samples)

Sampling date

Sampling place / Samples origin

Project

Special conditions in the soil (if the soil samples are polluted by for example heavy metals, if the samples are fresh and have to be kept in fridge, etc)

Information for invoice (name, department, project number)

After analyses (Inform about keeping, sending back or discarding samples. If no information is given on this, the samples will be discarded after 6 months of sending the results of the analyses)

List of samples (See instructions in the form)

Samples

Observations:

Pay attention about what type of samples is necessary for your test. In some cases it is necessary both, loose soil and cylinders.

Fill the form that you will find in the website: mark the analyses that will be performed and prepare the samples list. Do not use long names or codes (number codes maximum 6 digits).

Loose soil

(in bags, cups, boxes, containers, etc): Soil that has been prepared: air dried (max. 35°C, water content <5%), grinded and sieved at 2 mm, or fresh soil.

OBS: If the samples are not air dried grinded and sieved, the preparation will be done in the laboratory (see the price list).

FRESH SOIL: Send enough soil that for the different analysis according to the list below. Very important: do not send more than 2 kg.

• SOIL PARTICLE DISTRIBUTION: At least 100 g of prepared soil
• WATER CONTENT: At least 300 g of fresh soil
• LOSS ON IGNITION: At least 100 g of prepared soil
• WILTING POINT: At least 200 g of prepared soil
• PARTICLE DENSITY: At least 200 g of prepared soil

Soil cylinders

Cylinders can be rented from the Soil Physics Laboratory (5 or 10 cm height, 7.5 cm outer diameter, and 7.2 cm inner diameter).

The cylinders can be rented for short periods to collect undisturbed soil samples or to prepare samples and then to send them back to the laboratory. In the case of non-undisturbed samples, loose soil can be placed in cylinders and repacked to relevant density by the customer). To rent cylinders it is necessary to specify how many cylinders will be rented, for how long (the day to pick up and return), and which analyses that will be performed in the laboratory. It is also necessary to specify the need of sliding hammer or not for sampling, as lids and filter paper (for keeping the soil in the cylinder).

It is also possible to send us your own cylinders. In this case, a fee to handle them (washing etc) will be included. The transport costs to return the cylinders will be covered by the customer. If the weights of the cylinders are not provided, the raw data (cylinder+soil weights) will be sent as results.

• OBS1: If the samples have to be trimmed and/or have excavations that need to be measured for volume corrections it should be mentioned. Any need of volume correction should be specified in the order.
• OBS2: Keep rented cylinders in their respective boxes. The boxes should come back to the laboratory with all their respective cylinders.
• OBS3: Do not write, put stickers  or carve numbers or text on rented cylinders and lids since the cylinders and lids  will be used in other studies (any reference to the original numbers on the cylinders are referred to on separate sheet). Furthermore, such notes on the cylinders may disappear very easily in the transport and further handling.
• OBS4: If other material is also borrowed/rented together with the cylinders, all the material taken from the Soils Physics Laboratory should be brought back as soon as possible.
• OBS5: If there will be more than one analysis performed in the samples, it may be more convenient to take different group of samples for the different analyses.

Lab order form (excel sheet for download)

Contact us at soilphysicslab@slu.se

Department of Soil and Environment, Lennart Hjelms väg 9, Uppsala (Rooms A3071 and A3075) 

Delivery address

Department of Soil and Environment
Gerda Nilssons väg 5
756 51  Uppsala, SWEDEN
Tel +46(0)18-67 30 05

Opening hours: 08.30-15.00 (closed for lunch 11.30-12.30)

References for quality assurance of analysis methods: 

• Nimblad Svensson, D., I. Messing, J. Barron. 2022. An investigation in laser diffraction soil particle size distribution analysis to obtain compatible results with sieve and pipette method. Soil And Tillage Research Volume 223, September 2022, 105450 https://doi.org/10.1016/j.still.2022.105450

• Soil Physics Lab Annual Report 2022