Soil testing and sampling

At Greater Sydney local Land Services we
work with land holders from all
different size properties we like to
encourage those land holders to think of
their soil as an asset that they're
going to protect and manage and look
after better having the knowledge of
what's beneath the soil surface is
really important and taking soil samples
and having those samples analyzed is the
first step towards that knowledge as a
soil scientist we work with land holders
to identify the type of soils that they
have and to help them meet their growing
objectives soil testing really will
inform your management decisions it will
help you identify what your inputs will
be what your outputs are going to be and
how you're going to achieve those
targets naturally the seasons will
govern what kind of crops you're putting
in and it's really important to test
your soil before you're about to put in
your crops so once you've finished with
your spring Harvest
those those crops have taken out a whole
bunch of nutrients from the soil and
you're going to need to replenish them
before you put your summer harvest in
so testing is really important before
you invest in all of the time and the
labor and the money that you're going to
put in to your next Harvest
there are plenty of things that you can
test for yourself in the field
you can test soil texture by doing what
we call a ribbon test and that will give
you an understanding of the proportions
of silt and clay and sand we can test
for organic matter by simply seeing how
the soil can stain your fingertips we
can test for compaction and hard pans in
the soil by simply getting a rod and
seeing how much pressure you need to
exert to get through that soil profile
we can test drainage and the
permeability of your soil by taking a
known volume of water and essentially
just timing how quickly or how slowly it
will take to drain that water through
the soil profile and then of course you
can purchase a pH test kit around 20 30
and you can get those from hardware
stores or nurseries and and that's a
really simple way of measuring your pH
when we speak about topsoil could be
anything from sort of zero to 300 mil or
deeper or shallower in various sites but
that's the that's the Horizon that we're
really interested in in terms of Plant
Nutrition so when you're sending us a
soil sample what we'd like you to do is
collect around about a couple of
generous handfuls in a sealed bag when
you're collecting those samples try and
collect several sub-samples from within
that area and mix them together really
well we don't need a lot but we do need
to make sure that's representative of
the entire Paddock as I said put it in a
sealed bag try and retain some amount of
air in there because if you exclude it
all you can change some of the
microbiology or some of the chemical
processes that are going on in there
keep it in a cool area until you get us
get it to the lab generally we'd like it
within a day or two and finally when you
send us your sample make sure it's got
your contact details on there and the
type of tests you need so naturally
there are some costs associated with
testing your soils in a laboratory it
can range from fifty dollars up to a few
hundred depending on the type of tests
that you're having done but talk to your
lab or your saw consultant and they can
tell you exactly how much you can expect
to pay and how quickly your results will
get to you but it's really a small
investment that can lead to much bigger
cost Savings in terms of your Crop
Production greater Sydney local Land
Services has dedicated staffs that are
committed to helping land holders with
what they need as far as advice and
resources and information for their
properties they just need to feel free
to contact so they'll be put in touch
with the right person with the right
information to answer all their
questions

All farmers do their soil sampling that's  how they know their soil fertility levels.  
And that's how they know what they need to put  into their soil. The emphasis of our work has  
been to understand the precision around that,  and what those numbers really mean. 
Usually when we take a soil test farmers will go  out routinely they will take soil sample,  
they'll take 20 to 50 cores, mix all the soil  together and send that away for a whole heap  
of analysis.
Where we apply best sampling  practice that we assume a 15% level of precision  
So that means that the value that you  get on your soil test is accurate within plus or  minus 15%
The only way to improve our confidence  in commercial soil sampling is to make sure  
that we we take an adequate number of cores.  And so often what we find is we've got guys who  
might have paddocks which could  be 10 hectares there could be 50 hectares so it's  
quite a large area of land. Well obviously one one  core is not going to suffice it's not going to  
give you a very accurate or very useful estimation  of the fertility status of the soil.   
So what needs to happen then is we need to make sure that we  take enough soil cores. Now how much is enough?  
At a minimum we're saying that farmers or agronomist  should be taking at least 30 to 50 soil cores, and  
and if they do that they hopefully will achieve  their 15% level of of precision.
If you take less cores than that, then you're really reducing the  level of precision so maybe your so test value  
is only 20 or 25% or even less. And once  once the precision goes down the soil test value  
becomes relatively worthless. Other things that can  be done to ensure that we have good confidence is  
that we choose our sampling area correctly so if  we're in a 50 hectare paddock we're obviously not  
going to try and approximate the fertility for the  whole 50 hectare paddock, so what we might do  
is we might use other things like yield maps, or satellite images and NDVI or even just  
soil types you know if there's obvious soil types  we stick to a soil type and say either that's the  
best area or the worst area or the representative  area in the paddock. Stratification of pH means that  
in different layers of the soil profile the pH  changes. Now typically what that means is that  
at the soil surface pH is typically a little  bit higher but almost universally you would see  
a more acidic zone just below the soil surface. So  say in the the 5 to 15 cm zone, we would expect  
to see a lower pH compared to it the at the soil  surface. The problem with standard soil sampling  
technique, we usually use 10 cm increments so  you know we go out and sample agronomist goes  
in samples we take a sample at naught to 10 cm. That  means that volume of soil is all mixed  
up and averaged okay so there's no accounting  for stratification in that. But we know that  
the soil at the surface has a higher pH  than the soil below that. So rather than taking  
an average value of that what we try and do is we  try and sample that stratification. So we've take a  
smaller depth increment and we're suggesting 5 cm, so that we get the the higher pH is represented on  
the soil test in the surface but then we can also  identify actually how severe our acidity  
constraint is at that 5 to 10 cm layer. Our new  recommendation now to capture that stratification  
is to sample it 5 cm increments when we're trying  to monitor pH. So it's important to remember that  
soil sampling precision is a different  issue to to stratification. So precision is  
how reflective that number is of the true  fertility status of the soil. Stratification is the  
layering you know the difference with depth in the  in that soil property. So two key practical messages.  
One is if you're going to sample do it properly so  take enough cores and have a soil sample which you  
have confidence in. And the second message  particularly in regard to pH if we're trying  
to monitor and measure soil pH and manage our  acidity, we need to capture that stratification so  
we need to be sampling in 5 cm increments  certainly to the in the surface 20 cm at least.

Local Land Services work with a variety
of land holders on small properties and
large properties we think it's really
important to encourage land holders to
think of their soil as an asset and it's
to be protected and managed properly
having that knowledge of what's under
the soil surface is really important as
well because that helps make really good
management decisions when you make the
right management decisions you end up
with healthy soils and productive
pastures when it comes to soil
interpretation our experience Growers
will know how to interpret the test
results but novice Growers or beginners
may need to consult with a soil
scientist or an agronomist to be able to
interpret that result and turn it into
something practical so my role as an
agronomist I'm actually looking at how
those soil and the fuel tank that is
below us being been our soils actually
affect what we can actually grow on the
surface the the first point of contact
for a lot of Growers is that they'll
contact me and ask can they have a soil
test don't they want to find out what's
actually happening on their property so
the first point of call is I'll come out
to the property have a look at what's
actually happening within their
operation take those physically take
those soil tests for them
send them off for the grower when we
receive this the actual soil test back
for the client we can actually go
through and we're looking at a number of
different elements within this actual
soil test it comes with a lot of
information which would bamboos a lot of
people but you actually really take in
just some really key messages the key
messages are we're looking at your
micronutrients and your macronutrients
so macro has been your nitrogen your
phosphorus your potassium and your
sulfur and then really within the within
this Sydney Basin there's a lot of
micronutrients which are actually quite
deficient so copper Boron selenium
they're really critical to the actual
health of your livestock and your
pastures but if they're missing we can
tell that from from that soil test so
this actually gives us that information
I'm able to make an assessment from this
information for the client and then we
can actually put a proper program
together to give them that success once
you get your soil tests that's going to
inform your next steps which could be
ameliorating the soil with fertilizers
Street fertilizers complete fertilizers
or green waste compost for example it's
really about understanding what the
necessary inputs are in order to achieve
your outputs and and trying to get there
in the most productive
cost efficient and sustainable way
following on from actually having a
visit with the client and talking about
the plan and where the actual plan is
going their next step is to actually go
to a rural rural produce store talk to
her about what was suggested and
recommended within that program work
with their agronomist to watch products
are spec going to suit that they'll
provide those material to you and those
products from that point the client will
go back and then incorporate those or
use them within their system and then as
an agronomist as my role is to go back
out and check on their progress look at
the changes that have occurred and we
may have to do another soil test within
another 12 months of that time and we
can actually then Benchmark and measure
the change that has actually occurred by
introducing and copying those amendments
uh whether it's been a a big change or a
smaller change and do we need to adjust
our program to actually make it a little
bit more tailored to that particular
property my takeaway for land holders is
that it's really really critical to stop
listening to what's actually happening
out in the broader Community actually
focus on what's happening on your
property by carrying out that soil test
you've got your own answers you're not
worried about what Bob's doing down to
the pub first point of call talk to your
agronomist
get a soil test and then actually make a
proper plan because if you're doing the
proper planning you're going to get some
really fantastic results go to Sydney
local Land Services has dedicated staff
that are committed to helping land
holders with what they need as far as
advice and resources and information for
their properties they just need to feel
free to contact us they'll be put in
touch with the right person with the
right information to answer all their
questions