Worksheet PSD Physical and selected chemical methods of soil analysis,
IHLW, SS2018
Particle size distribution
combination of lab methods - fine sieving and sedimentation
Sample preparation
•crush air dry soil samples using moderate power to particles smaller than 2
mm, sieve them through a 2-mm-sieve, do not destroy coarse primary
particles (stones), remove organic matter, determine fraction of particles
> 2 mm, note mass → if it is greater than 10 % of the whole sample,
conduct dry sieving according to lecture notes
•prepare 2 soil samples: (i) 20 g (± 0.001 g) for sedimentation and (ii) 100
g (± 0.1 g) for fine sieving, note sample masses (
mges
), fill samples into
glass bottles, note bottle number
•add 50 mL (I) resp. 250 mL (ii) of dispergant, wait 8 h
•add 200 mL of de-ionised water, close bottle tightly, shake sample at
least 6 h in the over-head shaker
Fine Sieving
Measurement
•prepare sieving tower with sieves: 2,1, 0.63, 0.2, 0.125, and 0.063 mm
mesh size, reflect about the right order
•pour soil sample onto the top sieve, carefully wash soil particles out of the
bottle using a washing bottle
•close and fix sieving tower by appropriate lid, turn on water supply, start
shaking mode until no more particle are detectable in the outflow
•prepare 5 ceramic cups per sample, note masses on the form (
mSch i
)
•after shaking is completed, wash sieving residue into corresponding cups
•oven dry cups + samples until mass constancy at 105°C, let samples cool
down for ca 1 h, weigh and note dry masses (
mSch+s+w i
)
Equipment
for sample preparation and fine sieving
•Schott glass bottles, 1 L
•0.4n-sodium pyrophosphate as dispersant
•scales (precision 0.01 g and 0.0001g)
•sieving apparatus with sieves
(2,1, 0.63, 0.2, 0.125, 0.063 mm mesh size)
•ceramic cups
•washing bottle
for sedimentation method
•water pan on horizontal plane
•glass cylinders 1000 mL
•pipette 20 mL with vertical mounting system
•thermometer (precision 0.1°C)
•timer
Why do we measure?
Knowledge about the particle size of soil
allows a relevant physical classification of
soils into textural soil types. The
classification gives a good idea about
properties of soil like water regime or
infiltration capacity. Textural soil type is
mapped in official soil maps like eBOD
(online map for Austria).
In Practice
Some background information
Hereby, the distribution of primary
particles is measured. These are the
basic soil material and their distribution is
not changed by human management.
