I have ~20 g soil samples from Tanzania which I would like to wet sieve and identify mycorrhizal spores to measure abundance/diversity, and also a few thousand 6 g samples from various sites around the UK. Is 20 g enough sample to get good quality and publishable data from? What about 6 g?
Many thanks in advance.
Dear Naomi Rintoul,
I advise to see the standard provided by APHA methods but if APHA not provide any specific methods it is better adopt others scholar used when they perform the same kinds of experiments
Dear Rintoul,
There is no universal rule for the sample size for accessing the diversity of AM fungi. Because of various kind of spore formation (i.e., free spores in soil, spore aggregates, compact/loose sporocarp formation, more intraradical spore production) in AM fungi, by following any single published method one can not access the whole diversity of spores.
The amount of soil sample to be taken is the function of many factors, like, soil texture, humus contents, associated AM fungi, etc. 20 g soil sample is more than enough for going through wet sieving and decanting. There may be following problems you will face through this quit large sample.
1. Soil may not be blended/mixed thoroughly resulting in less resolution about the AMF community.
2. The lower content may be filled with clay, which will require further processing like density gradient centrifugation, which ultimately affect the count.
In general, I suggest you to go through the small soil samples (less than 5 g) and increase the number of replicates. Further, while collecting the soil samples, follow some standard sampling methods (like, random, systematic, stratified, etc.). What ever, the sieve size you take, analyse all the sieve contents, because of various size range of AMF spores.
Kind Regards,
O Akhtar
It depends upon your spore density. In arid soils where spore density is very less we found that 50g soil is the optimum. But where your spore density is more (>400) you may find 10g soil is also sufficient . But below 10g is not advisable.
It is density dependent. If you have any bigger sample, you could get a serial increase in the sample size and plot your results to analyze how it behaves to determine the optimal sample size/diversity ratio that you have for your soil type.
I thing 20 gm soil is ok. but if the spore no is very high, then you can use less soil...
5g soil mixed in water and shake for some time till all particle homogenised. After settle to soil in lower portion. Upper water sieve. collect the spore with water and sieve the water in filter papers. count the spore/g of soil and collect the spore through needle. thanks
I agree there is no minimum soil sample size (in g) that should be used but from experience I think 20 g from a field soil is not enough. If the site was inoculated, then maybe that´s OK or you can even go lower otherwise I would expect quite low density and therefore more soil material for reliability.
In my opinion 20 gr soil that is not enough for examine the spore ...
i used about 50 gr for counting number of spore.
I always use 10g of sample as a standard to evaluate the spore numbers in the commercial AMF product.
Dear all,
Thank you very much for your responses - as I have fairly small samples of soil for my current experiment, I have gone with about 10g. I will bear this in mind when collecting further samples and ensure I have 20-50g for spore ID.
Naomi
20 g of soil is enough. 6 g is not at all sufficient. Because the AM Fungal propagules may not be available.
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