Soil Testing Methods Chapter 8. Soil Analysis Ch 82 Three approaches Observations in the field On ‑ site measurements Laboratory measurements

Soil Testing Methods

Chapter 8

Soil Analysis Ch 8 2

Three approaches

Observations in the field

On‑site measurements

Laboratory measurements


Field Observations Field observations of properties which can be observed

after digging a soil pit

Semi‑quantitative assessments of properties rather than direct measurements.


Field Measurements On‑site measurements using equipment inserted into soil,

without significant disturbance of the soil.

This approach applies particularly to soil water studies.


Laboratory Analysis Measurements made in the laboratory on soil samples

taken from the field.

Sub-sampling down to an analytical sample also occurs


Soil Survey Reports

what kinds of soil exist in an area

described in terms of location, profile characteristics, relationship to each other, suitability for various uses, and needs for particular kinds of management

two major parts in a soil survey report: the soil map the narrative


SALIS

NSW soil survey database

Soil And Land Information Service

run by Dept of Natural Resources

http://www.dnr.nsw.gov.au/soils/about_salis.shtml

Field Analysis of Soils

How can we Analyse Soil in the Field?


Field investigation soil pits

expose the soil profile and horizons allow field testing of parameters that would be

destroyed by cores in-situ testing devices semi-quantitative assessments

field data minimises sampling error

does not guarantee reliable or even consistent data

soils have very poor homogeneity


Soil Pit

from www.drm.gov.au


Choosing Sites for Soil Pits

Avoid

areas close to gateways, paths and tracks

headlands of arable fields (the outer 10 m)

sites where straw or fertiliser have been stored

sites used for localised burning of crop residues or hedge trimmings

old field boundaries where a hedge or bank has been removed and the land levelled


Choosing Sites for Soil Pits

soil varies spatially (from one place to another)

some properties vary in time

eg nutrient levels, moisture

others are more permanent

horizon depth, texture, stone content and ion exchange capacity

How do we Sample Soil?

Is it just digging holes?


Sampling questions

How many samples do I take?

Do we composite lots of sub samples?

How deep do we take the samples?

Do we replicate the sampling?

What quality control do we need?

What tools do I need?

How do we transport, store and prepare the samples?


Information we need to know Why are we analysing the soil?

Surveys, chemical analysis etc.

How large is the area of interest? Large areas require lots of sampling

Do we now the soil profile at all? If we don’t, how deep do we sample?

What are we analysing the soil for? Physical, chemical or biological parameters


Amount of sample depends upon;

Time constraints Topography Cost factors Reasons for sampling There are no specific guidelines


Soil Sampling

undisturbed stratification:

remove a core with all horizon information retained, eg with auger

disturbed stratification

no attempt to keep the vertical connection between horizons, eg with a shovel


Soil Sampling

How many samples do we take?

At least 20 single samples per 10 000m2 must be taken with an earth boring tool (or spade) and combined to a mixed sample.

To what depth do we sample?

The usual sampling depth is up to 20 cm in arable land or 10cm in pasture. Undisturbed soil samples are obtained with a cutting cylinder with minimum capacity of 100cm3 .


How do we sample?

test lotrandom diagonal line cross line


Sampling using Augers

pressed and rotated into the soil to take samples from depth increments of between 15 and 20cm.

samples are 'disturbed' to varying degrees

observations that can be made on the samples will be restricted

colour, texture, stones, roots and horizon depth can be recorded

soil structure cannot

special coring equipment is required to obtain 'undisturbed' samples


Sampling for lab testing

normal sampling depth for horticultural and tree crops is 0-15 cm

deep sampling down to 60-100 cm may be necessary to better assess soil salinity, acidity, S, and mineral N status

sampling depth must be recorded

protocols relevant to important crop and soil tests should be followed

usually involves making a composite from around 15 to 30 sub-samples from the area in question

Transportation, preparation and storage of samples

Now that you have your soil samples, what do you do with them?


Laboratory Preparation of Samples

should be kept cool or cold between during transport

may be air-dried remote from the laboratory (max. 40C) when moisture content is not required

breaking up any large cores or peds on a clean surface

remove rocks by hand or sieving

retain a representative portion in a sealed polyethylene bag or 'moisture container' for moisture determination

sample size reduction: coning and quartering or riffler




Laboratory Preparation of Samples Next spread the soil samples on drying trays (if applicable)

and air-dry at up to 40C.

When the soil is thoroughly air-dry, mix, roll, and/or grind.

Retain the <2mm fraction, preferably in an air-tight plastic or inert container, for subsequent laboratory analyses.



When required, determine the weight percentage (oven-dry basis) of the residual >2-20 mm size fraction.

When fine grinding is specified, take a representative sub-sample (usually around 30g) from the <2 mm portion.

Pass the entire sub-sample through the required mill and store in a small air-tight container.


Coning & quartering


Riffling

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Soil Testing Methods Chapter 8. Soil Analysis Ch 82 Three approaches Observations in the field On ‑ site measurements Laboratory measurements