The cost (in Australia) is usually significantly less than
what the accountant charges for preparing the farm tax return.
Surprisingly, for this number of samples, the cost of
measuring soil carbon on a 90 ha cane farm in Northern NSW and 10 000 ha mixed use
farm in Western Australia is about the same. We have found that areas of
commonality, known as unequal strata, does not vary significantly with farm
size and therefore number of sample locations do not vary greatly. Our
method developed by University of Sydney requires, in order to minimise error
to trade carbon and to produce a quality carbon distribution map, between 60
and 90 samples depending on the local factors of the farm. With a
specialist, trained experienced soil sampling contractor around 100 locations
can be sampled to 30cm in one day. When driving between locations on the
farm increases such that sampling takes longer than a day, sampling costs
increase. But laboratory and calculation costs remain the same.
Thus, the limitation becomes not the number of samples but the time taken to
travel between sampling locations in a day.
Combustion methods are currently the cheapest. The
advantage of the combustion methods is that nitrogen can also be measured for
less than $2/test extra. Any laboratory with national accreditation in
combustion methods assessment can be used.
When accredited sampling and testing contractors are used
sampling and laboratory costs are between 80-90 % of the costs.
The cost of calculation and royalty of the research institution makes up the residue.