Module 01 >

Monitoring Soils

Module 02 >

Interpreting Soil Results

Module 03 >

Soil Fertility and Nutrient Management

Module 04 >

Common Soil Constraints

Module 05 >

Soil Carbon Capture

Module 06 >

Digital Agriculture for Soils

Module 07 >

Using Biologicals to Build Soil Organic Matter and Resilient Soils

Module 08 >

Managing Irrigated Soils in the Riverina Region of NSW


Monitoring Soils

Module 01 >

Monitoring Soils

Module 02 >

Interpreting Soil Results

Module 03 >

Soil Fertility and Nutrient Management

Module 04 >

Common Soil Constraints

Module 05 >

Soil Carbon Capture

Module 06 >

Digital Agriculture for Soils

Module 07 >

Using Biologicals to Build Soil Organic Matter and Resilient Soils

Module 08 >

Managing Irrigated Soils in the Riverina Region of NSW


Why test soil?

Soil testing is a vital tool to identify issues affecting profitable crop and pasture production. Knowing how to best manage the soil means first understanding soil chemistry, physics and biology.

  • Soil testing is a vital tool to identify issues affecting profitable crop and pasture production. Knowing how to best manage the soil means first understanding soil chemistry, physics and biology.
  • Soil is inherently diverse and farm management practices add to the diversity. For example, no-till and precision fertiliser placement lead to nutrient bands in the soil, rather than evenly distributed nutrients.
  • Understanding soil nutrient stocks is critical to best practice crop nutrition.
Farm management decisions made on evidence gathered from proper soil testing ensure improved soil health and plant
nutrition and protect environmental health.
Soil sampling is usually undertaken for four main reasons:
  1. Fertiliser planning. Which nutrients are needed and how much?
  2. Diagnosing a problem. Is a soil issue the reason behind poor crop or pasture growth?
  3. Monitoring. How soil properties are changing over time.
  4. Compliance. Does the status of soil in farm meet required environmental standards.

The 4Rs of good
fertiliser management.

Cost effective fertiliser decisions hinge on adhering to the 4R’s of fertiliser management – the right nutrients, at the right rate, at the right time, in the right place.

Soil diversity must be addressed when sampling soil

Soils can change from one meter to the next.
Understanding and capturing soil variability is essential for getting useful soil test results.

Soil diversity

Soils are inherently diverse, changing down the soil profile and across the landscape. Variations in soil texture, pH, nutrients, salinity, compaction and more affect crop growth and how paddocks need to be managed. Agricultural practices such as tillage and fertiliser strategies further compound soil diversity.

Without a thorough understanding of soil diversity, soil samples may not provide an accurate representation of the overall soil health and nutrient status, leading to incorrect soil management decisions and potentially lower crop yields.

From an environmental perspective, understanding soil diversity can also help identify areas where soil erosion, nutrient leaching, and water pollution are most likely to occur.

When should I soil sample?

Weather and busy schedules mean sampling often happens when you get a chance. Best practice is to sample:
  • One month before fertiliser applications or seeding. This gives you enough time to get the results and work out the fertiliser strategy.
  • Three to four months before seeding if applying soil amendments such as lime and gypsum. This allows enough time to apply the amendments and for them to take effect.
  • At the same time each year. Soil nutrient levels vary throughout the year. Sampling at the same time makes it easier to compare the results.
  • Preferably when the soil isn’t too dry as this affects nutrient availability.
  • Whenever you have the time if sampling to characterise a new block to work out a farm plan, or understand soil constraints, (and there is no pressure to plant).

Did you know?

Sampling should not be done if the site has been fertilised or had an amendment applied in the last three months.

Where to sample soils

Where you collect soil samples ultimately depends on why you are soil sampling. For example, the sampling strategy for developing a fertiliser plan will be different than the strategy for identifying physical or chemical soil constraints such as acidity and compaction. Ask yourself, why am I sampling and what am I hoping to learn? This will guide the sampling plan.


Soil sample locations will depend on why you are sampling. Make a sampling plan with sample locations, the sampling pattern, and areas to avoid before heading into the paddock.


Sampling plans

Always develop a sampling plan before heading out into the paddock. Sampling plans mark out where you will sample and areas to avoid sampling.

Digital vs hardcopy plans

Digital Plans.

  • Some precision agriculture platforms include a sampling feature to mark out sample locations. These are helpful in very large paddocks as the GPS feature shows if you are sampling where you intended or have gone off course. Many map platforms (including apps on your phone) allow you to download the map area before heading out to the field, which is necessary if there is limited internet or phone reception.
  • Digital plans are problematic if reception or internet coverage is poor. Printing off the plan first solves this issue.

Developing the sampling plan

Creating a sampling plan has five main steps.
  1. Choose paddocks
  2. Shade out areas to avoid
  3. Choose a topsoil sampling pattern
  4. Number of cores and composite samples

1) Choose paddocks

Farms are usually too big to sample all at once. Start by choosing which paddocks need sampling. Many broadacre growers choose to sample about one-third of the farm each season.

Hardcopy plans.

  • Many sampling plans are hardcopy because they are easier to work with and have fewer technical glitches. A printed aerial image of the farm or paddocks to sample is a good start.
  • You can make a sampling plan by choosing locations on Google Earth or similar, then printing off the map.

2) Mark out zones

Sampling the whole paddock without first thinking about paddock variability is only useful if you can afford to have each sample tested individually. If budget is not an issue, grid sampling a whole paddock can give a good overview of paddock condition and help identify where soil types change.

However, budget is usually limited and samples are bulked together to make composite soil samples. If samples from different soil types and management areas are lumped together, the test results will not form a good basis for the follow-on soil management strategy.

Did you know?

Composite samples combine individual subsamples into one sample. This is done to save money and make a representative sample of an area.
Dividing the paddock into zones helps capture soil diversity and makes sure the composite soil samples that are sent to the lab are representative of that  one. Zones are marked out based on soil types, yield variation, etc. – areas we want to keep separate. The key point is that each zone represents a relatively uniform area of yield, soil type, or management.

Sampling from the same soil type, cropping history and management reduces the number of cores required to get a representative composite soil sample.

How to mark out zones

Yield maps, aerial photographs, landscape maps (e.g. topography, hydrology), NDVI, soil maps, EM-38 maps, ConstraintID and other farm maps can be used to develop the sampling plan. For example, if the point of sampling is to identify the cause of yield differences, mark out sample locations in areas of both ‘good’ and ‘poor’ yield.

The Example sampling plan shows how to use various spatial layers to choose sample locations.

Figure 1.1 Examples of ways to divide the paddock based on soil changes (b), different management (c) and both (d).

Figure 1.2 An example of dividing paddocks into zones based on topography.

3) Shade out areas to avoid

Once different zones are marked out, shade or cross out areas to avoid when sampling. Areas to avoid are where the soil is clearly different from the rest of the field or zone, such as:
  • Bare ground, unless you are trying to diagnose the cause or most of the paddock is bare
  • Small patches of very good growth likely caused by urine or dung
  • Within 10-20m of fence lines (current and old), dams, gates, and troughs
  • Where stock walk, camp, and feed
  • Small depressions (e.g., melonholes)
  • Hay or lucerne storage areas
  • Under tree canopies
  • Areas where fertiliser or lime has previously been dumped
  • Old fire piles Poorly drained areas
  • Headlands
  • Corners of paddocks that have been cultivated or planted from the perimeter inwards
  • Old building sites
  • Severely eroded areas.

4) Choose a topsoil sampling pattern

Choose a sampling pattern to use within each zone. The patterns below are for paddocks that have not had banded fertiliser applications. See section ‘special sampling situations’ for sampling paddocks with banded fertiliser.

On balance, the zig-zag pattern is the best method in terms of repeatability, labour efficiency, and likelihood of getting a representative sample.


It looks like you are collecting a lot of samples, but they will be mixed together to make composite samples.

Sampling patterns within zones.


Random locations

More likely to get a representative sample

Hard to replicate for monitoring (unless you GPS every subsample)


Collect soil samples in clusters around different points.

Faster to collect than other sampling patterns Easy to repeat for monitoring

Less likely to get a representative sample

Grid sampling

Divide the zone into a grid

More likely to get a representative sample

Time consuming


Collect soil samples along a zigzag pattern across the field.

Can provide good coverage of the sampling area More representative than transect sampling

Can be time-consuming and may miss pockets of soil variability


Random locations

More likely to get a representative sample

Hard to replicate for monitoring (unless you GPS every subsample)

Special sampling situations

Crop rows and fertiliser bands

Cropping paddocks with banded fertiliser need a specific sampling pattern. If planting between last year’s rows, collect one sample on-row and about six samples in the inter-row. Section 6.5 of the Fertcare “A guide for fit-for-purpose soil sampling’ gives more detail and a calculation to work out how
many cores to take.

Sampling for soil pathogens – Predicta B

Sampling to test for soil pathogens requires a different sampling process and tools. Predicta-B soil sampling is usually done via production zone and two specific corers are recommended. Detailed instructions for Predicta-B sampling are available via the link below:

5) Number of cores and composite samples

Even though you are working in zones of similar properties, the soil will still be highly variable. One soil sample will not give you a good idea of what’s going on in the paddock. Accurate soil test results come from representative soil samples that reflect the conditions in the zone. Representative samples combine multiple cores, usually >25, into one composite sample.Composite samples average out soil variability within a zone, providing a more accurate representation of the soil in the sample areas and reducing the cost of analysis.

Generally, the larger the zone, the more samples and subsamples will be needed to collect a representative soil sample.

Subsoils are often less variable than the topsoil and need fewer cores. The number of samples collected for analysis will depend on subsoil variability and budget.


Collect 25+ cores per composite sample

The example sampling plan below shows a completed sampling plan for a paddock near Wagga Wagga.

The full process undertaken to develop this plan is outlined here.

Figure 1.3 Example sampling plan


How to collect samples

Accurate soil sampling matters

Laboratories typically use only about 10-20 grams of soil for chemical analysis. This is about 0.00001% of the field soil being assessed (see Figure 1.4 below). 

Useful lab results therefore depend on:
1. Choosing representative soil sample locations
2. Collecting the soil sample properly.
Figure 1.4

Sampling tools

There is a wide range of soil sampling tools available, with multiple variations on corer and auger design to cope with situations such as very sandy soil, gravel and wet soil. It’s ideal to have dedicated topsoil and subsoil sampling tools. Subsoil sampling uses different tools to the 0-10cm topsoil corer. For hand sampling, a soil core or push tube are common tools. These are essentially steel pipes that are hammered into the soil to collect the core.

Choose tools that:

  • Won’t rust
  • Are easy to clean
  • Are sturdy
  • Are not galvanised.

Pogo stick

Pogo stick or foot corer.

Good for: topsoil sampling

Not used for: subsoil sampling

Push Core

Good for: subsoil sampling

Cores made from chromoly are stronger and less likely to bend.


Good for: checking deeper soil layers

Not used for: sampling for nutrient testing

Shovels aren’t usually recommended for soil sampling because they collect a tampered sample. Best practice is to collect the same volume of soil from each sampling depth. However, shovels are useful when you need to see what’s going on a depth, such as where crop roots stop or choosing subsoil sampling depths.

Spiral auger

Spiral auger or post hole digger with a spiral in the centre.

Good for: checking deeper soil layers

Not used for: sampling for nutrient testing

Spiral augers aren’t recommended for nutrition sampling. They are useful if you need to examine the soil at depth, such as finding subsoil depth, gravel layers, or depth or root growth, but aren’t collecting samples from dedicated depths.

Sampling tips

Most topsoil corers collect samples 10 cm in length. If you need to collect shallower samples, such as 0-5cm, this video shows how to collect soil samples from smaller depths. The process is similar to collecting subsoil samples. Another approach is to take “bites” of the soil with a push probe or pogo stick style corer. Insert the tool 5cm into the soil, remove the sample, then insert it for another 5cm to collect 0-10cm depth in two 5cm intervals. This can work if the soil isn’t well structured enough to easily divide the whole core.

Mechanised sampling

Power augers/ute mounted corers (see Figure 1.5 below) make sampling faster and more efficient if sampling during summer. They are useful for collecting subsoil samples, particularly where the subsoil is hard and difficult to dig. Key things to check are that they can collect a standard volume of soil. Tube samplers can be difficult to use on dry sandy soil as the samples can fall out the bottom when the core is extracted. Sampling dry, sandy soil is covered more in section ‘Notes on wet, clayey, and very sandy soils’.

Equipment list

  • Sampling tools for topsoil and subsoil
  • Plastic bucket to collect composite soil samples
  • Tape or other measure to measure soil layer depths
  • Spade (if collecting subsoil samples as well)
  • Auger for deep coring (if collecting subsoil samples)
  • Collection tray for subsoil samples. A piece of plastic pipe cut in half works well, or a piece of clean and non-galvanised corrugated iron.
  • Camera/phone to take photos.
  • Sample bags. Some labs can send sample bags in advance, otherwise a sturdy plastic bag e.g. sandwich bag is big enough for chemical analysis
  • The sampling map
  • Permanent marker/pens to label sample bags and sampling map
  • Optional: pH test kit to crudely assess soil pH; can be handy to decide if samples should be collected for laboratory analysis to accurately measure soil pH.

How deep do I sample?

The ideal sampling depth depends on the purpose of soil testing. While topsoil (usually 0-10cm) sampling is standard, plant roots grow beyond 10 cm depth and will use nutrients and encounter issues deeper in the profile. Farming on raised beds, perennial crops, irrigated rice, and cotton, usually sample to >50 cm depth. Subsoil sampling is critical in the Riverina due to the high variability in soil types and thelarge amount of duplex soils.


Plant roots grow deeper than 10 cm.
Sample both the topsoil and subsoil. Collect samples within soil horizons (layers) rather than at regular depths if trying to identify a soil constraint.

Standard sampling depths or soil horizons?

Soils have horizons (layers) that don’t always match neatly with standard sampling depths. Whether to sample at regular depths (e.g. 0-10 cm, 10-30 cm, 30-60 cm, and 60-90 cm) or within soil horizons, depends on the reason for sampling.

If the purpose is nutrient testing, standard sampling depths are more common. This is because most of the reference material with critical crop nutrition values works with standard sampling depths, making it easier to compare the results with the references. Practices such as ploughing to 30 cm, common in cotton farming, mixes horizons anyway making sampling at regular depth intervals necessary.

If the purpose of sampling is to identify soil constraints such as a layer of acidity or salinity, sample within soil horizons. Duplex soils are common in the Riverina, and in this case, it is important to make sure soil from the heavier layers at depth aren’t mixed in with the lighter/sandier soil layers above. Sometimes, identifying soil acidity or stratified cations means sampling in smaller (5 cm) increments within the horizon.

Figure 1.6 Profile of red Chromosol from the Riverina.

In Figure 1.6, note how the soil layers change at 5 cm, 15 cm and 25 cm depths in the middle of a standard 30 cm sample depth. In this situation, it is better to collect samples from 0-5 cm, 5-15 cm and 15-25 cm and below 25-30 cm, and not mix soil from two different horizons.

Collecting topsoil samples

Start with clean tools. For topsoil samples, set the tool to the desired depth or mark out 5 – 10 cm increments so you are sampling from the same depth every time.
  1. Remove any debris such as leaves from the soil surface.
  2. This is especially important for carbon testing. Don’t pull up plants as this will remove some of the surface soil.
  3. Push the sampler straight into the soil to the chosen depth.
  4. Turn/twist the sampler then pull it out of the ground, making sure soil doesn’t fall out the bottom.
  5. Tip the sample into the plastic bucket and move to the next sub-sample location.
  6. If only part of the core comes out with the sampler, discard that core and re-take the sample. Continue until you have collected all the cores that will form one composite sample.

What is wet, clayey and very sandy soil?

If the soil is very sandy and dry it might fall out of the tube or corer. When the sampling tool is in the ground, push the handle towards the ground so the tool is almost horizontal, then pull it out of the soil and put the subsample in the bucket.

If the soil is clayey and wet it can shear down the sides of the sample. Making sure you are collecting only from the desired depth will help reduce sampling error. Even better, don’t sample when the soil is this wet.

On heavy clay soils putting a paper clip on either side of the corer can make sampling easier. The paperclips help break surface tension and extract the core without causing compaction. This technique is more common on Vertosols. There is a small risk of contamination depending on what the paperclip is made from.

However, when a DPI researcher tested contamination by physically grinding up the paperclip into the soil sample, iron and manganese were only slightly inflated.

Getting stuck – tips and tricks

Sometimes, the soil can get stuck inside the corer, and the corer can get stuck in the ground when subsoil sampling. This more common on wet, clayey, or compacted soils. Lubricants can make sampling easier, but don’t use a lubricant unless you have to.

If sampling for nutrition, the lubricant must be silicon based. If sampling for soil biology or carbon, you cannot use a lubricant as it will inflate the results.

Don’t put too much on. Squirt a little on a bottle brush (or new toilet brush) and push the brush up the tube. A light coating is enough to make the core easier to extract. A light coating on the outside of the corer helps if the corer is getting stuck in the ground. This is more common during subsoil sampling.

If the core is stuck, don’t hit the tube on the tip end to get the soil out. If the soil won’t come out easily, it’s probably not a good core for analysis. Try using paperclips or a lubricant and re-take the core.

Composite samples and sub sampling

Once the 25 or so topsoil cores are in the bucket, you will have far more soil than the lab needs for analysis.

There’s no point in sending kilos of soil because it’s unnecessary freight expense and the lab will only use about 20 grams.

Mixing the composite sample in the bucket tries to make sure each core contributes equally to the final sample sent to the lab. Break up the cores into small crumbs and mix thoroughly. Scoop about 500 grams into the soil sample bag and label with the date, paddock name, depth, location, and any other information you need so that when the results come back you know where the sample was collected from.

Wipe out the bucket and tools before moving on. Make sure you have noted on the sampling plan which subsamples went into the composite sample

Collecting subsoil samples

  1. Remove the top 10cm of soil with a spade.
  2. Use the subsoil sampling tool to collect a core to about 50 cm depth (or as deep as you want to sample).
  3. Remove the core and slowly push it into the collection tray, keeping the core intact.
  4. Collect subsoil samples from within the soil layers. Put them in separate, labelled bags noting sample location and depth.


You do not need to collect as many subsoil samples as topsoil samples.

Sampling for bulk density, soil pathogens and soil constraints

Soil bulk density, pathogens and soil constraints have different sampling procedures to nutrient testing.

Bulk density

Soil bulk density is an indicator of soil compaction and is used to calculate soil water and nutrient stocks (kg/ha). Different coring methods affect bulk density readings. Percussive tools sometimes used for sampling, like post drivers, will compact the soil and inflate the bulk density reading. The size of manual corers can also affect compaction while sampling, with narrower cores increasing the risk of compaction. Pushing the soil sample out of the corer can also compact the soil. Pages 74 – 79 of Soil Matters give detailed instructions on collecting soil samples for bulk density testing.

Sampling procedure for soil pathogens

Reminder! The sampling process for pathogen testing is different to fertility testing. Incorrect sampling will lead to an underestimation of stubble and crown borne diseases, such as crown rot. Soil samples must be sent to SARDI in Predicta B soil kits, available for free. Details on how to collect soil samples for pathogen testing are outlined in the link below:

Sampling procedure for soil constraints

If the purpose of soil testing is to identify a soil constraint, such as an acid layer or other chemical issue, the sampling depth will depend on where you think the issue is. The best method is to check how crop roots are growing during the season and see where they stop. Collect a sample from just above where the roots stop, and another from just below where the roots stop. Package these samples separately, labelling them clearly with the depth collected. Common chemical issues include pH (acidity or alkalinity), salinity, boron and chloride.

For acid layers in the topsoil, sample at 0-5cm and 5-10cm. You can test for dispersive soil yourself or send the sample to the
laboratory. The Emerson Aggregate Test or ASWAT tests are the best methods to test for soil dispersion. Don’t test exchangeable sodium per cent (ESP) to gauge soil dispersion, as soils with an elevated ESP do not always disperse. Knowing ESP is useful if you think high sodium levels are hindering crop growth.

Sampling Hygene is important for accurate test results.

When sampling:

  • Use new, clean sampling bags
  • Don’t touch the soil with your bare hands.
  • Wipe down equipment when moving to a new set of composite samples.

To prevent disease spread, after sampling or before moving to a different farm, clean:

  • All sampling equipment
  • Your boots
  • Vehicles (tyres, wheels, etc.)

Keep good records

Good records are essential to tie the laboratory results to the paddock. Making notes on the sampling plan, and noting GPS
coordinates for sample locations are critical.


There are many free GPS apps. Aim to GPS each location you sample, recording the waypoint name periodically on the sampling map. For cluster sampling, GPS in the middle of the cluster. For transects and zig zags, GPS a few locations along the path. In order to repeat the sampling in the future, grid and random sampling patterns need GPS points at every subsample location. Knowing where you sampled is useful:

  • So you can repeat the same sampling pattern later (use the same path but not exactly the same points the next time).
  • If odd results come back and you need to check something in the field.

Composite samples

On the sampling map, draw circles around cores than have been composited into one sample.


Accurate records help you make an accurate fertiliser plan and if necessary, work backwards to find the source of odd laboratory results.


Sending samples for analysis

Selecting a service and posting your samples.

Where to send samples for testing?

Selecting a soil testing service

Sampling procedure for soil pathogens

Reminder! The sampling process for pathogen testing is different to fertility testing. Incorrect sampling will lead to an underestimation of stubble and crown borne diseases, such as crown rot. Soil samples must be sent to SARDI in Predicta B soil kits, available for free. Details on how to collect soil samples for pathogen testing are outlined in the link below:

Packaging and posting soil samples.

If soil sampling takes more than a day you will need to store samples and send the lot off to the lab once sampling is finished. Try to send samples within a few days of collection as mineralisation can occur which will change the nitrogen values.

The soil samples should already be in labelled sample bags. If the soil is wet, leave the tops of the bags open until they are ready to post. Store the samples in a dark, cool, dry area until they are sent to the laboratory.

Use Express Post or a courier for speedier delivery.

Quarantine issues

There are State and Commonwealth Government regulations that apply when transferring soil and plant samples to prevent soil borne pests and diseases from spreading. Restrictions may be applied on movement of samples, or requirements for treatment of soil from areas known to be infested with particular pests or diseases.

However, this is not an issue if you are sending soil samples within NSW for standard agricultural testing.

How often to test?

Test nutrients annually for fertiliser plan.

Every three years for pH and other soil properties.

As needed if there are problems during the growing season that could be from a soil issue.

What to test for?

Most laboratories have standard agricultural packages covering the basics including pH, salinity, organic matter and nutrients.

Some test methods are better suited to different conditions. For example, the DGT phosphorus test was developed for high pH soils, as other test methods over-estimate the amount of phosphorus. For trace elements, the EDTA extraction is more reliable in acid soils, and DTPA is more reliable on alkaline soils.

Talk to your agronomist to choose the best test methods.


Sampling tips:

Soil information

The Australian Soil Classification

eSPADE – an online tool with modelled and measured soil properties in NSW

ConstraintID - an online tool with which uses historical (from 1999 onwards) and current satellite imagery to generate maps of selected paddocks, showing parts of the paddocks which perform consistently well or poorly.

Frequently asked questions

Collect at least 25 subsamples to make a composite sample.

This will vary based on the size of the zone.
The number of samples needed for a 100-hectare dryland cropping paddock is different to the number needed for a 10-hectare vineyard paddock.

Collect at least two composite topsoil samples per zone, and at least four if the zone is larger than 20 hectares.

Work out the location and orientation of the transect.

Determine the sampling interval. At least 30m is ideal.

Mark the sampling points on the sampling plan Collect samples and GPS each location.

Choose your nearest soil testing service accredited by The Australasian Soil and Plant Analysis Council (ASPAC) or National Association of Testing Authorities (NATA).

Yes. Crop roots grow deeper than 10 cm. A good fertiliser plan will consider crop nutrients in the root zone, not just in 0-10 cm.

Collect soil samples one month before fertiliser applications, and three to four months before seeding if applying soil amendments.

Collect samples at the same time each year.

Test the soil each year to update your fertiliser plan, every three years for soil pH, and whenever necessary if there are problems during the growing season that could be from a soil issue.

Module 2

Interpretation of
 Soil Test Results