It depends on how soil sample are kept from nutrient depletion and also the type of sampling method used (composite or monolith samples). The best sample are well kept, the better. 

As Zacharie wrote it depends. I think not only on the type of sampling and storage conditions, but also on soil property. Actually, we can suppose many things, but it is impossible to verify. It can be supposed, that in air dry samples stored in proper conditions (not too hot, low humidity?) majority of properties will not change greatly for many years, although we cannot exclude slow mineralization of organic matter (so - small changes of organic carbon and total N contents). We can also suppose that such properties as mineral N will volatilize.More or less in 1999 I was analysing soil samples from 1974, but I don't know the results obtained in 1974.

I know about one study concerning the time of soil sampling and storage period of soil samples (up to 7 months only) - it is in Polish, with Russian and English abstract:

http://ssa.ptg.sggw.pl/artykul/436/preliminary-findings-of-investigations-on-phosphorus-and-potassium-content-and-ph-of-soils-in-relati

They did not  observed any changes of pH, P and K contents.

Yes I agree with Dr Stepien, there will be no change in 6 or 7 months if samples are oven dried and kept in cool and dry dark place. In fact, samples with high OM content could be mineralized but due to the low moisture content, it will be neglected. Soil samples can be stored up to 4 years along like than with no problem. For long periods (more than 4 years) they should be lyophilized, microorganisms are stored like that up to 10 years, why not soil samples?

It is a relevant question for researchers working on soil biophysical and chemical properties. It may depend on the types of parameters to be analyzed and the storage temperature. For example, if soil biological properties such as microbial biomass and soil physical properties such as soil aggregates are of your interest, they need to be analyzed as soon as possible after sampling, otherwise there may be a change in few days. Storing soil samples for months long may  not guarantee in obtaining the desired analytical values. In most cases, storing soil samples at a temperature of not more than 4oC is recommended.

If the analysis is mainly focused on soil chemical properties including soil pH  and exchangeable cations, the samples may be stored longer. For instance, a study indicated that Na and Al content decreased from 20-30% within the first two years with no further change in the following years. In general, care should  be taken in the interpretation of results obtained from the analyses of soils stored for a long time. The attached paper may give you further information.  

Thank you Anoop Kumar for asking a very good question of practical importance. I am also thankful to Dr. Stephien and Dr. Agegnehu for presenting nice and elaborated answers. Storing of soil samples and then keeping these pending for longer periods is a common practice in many labs, sometimes due to load of work. No body cares for the changes that would have occurred. The required cares ignored are:

1. Storing samples without bringing the soil to the standard temperature set for different determinations (mostly air dried, 4C etc.)

2.  Keeping stored for ove-rperiods

3. Storing at a common temperature ignoring determination to be carried out, though it is attached to the type of analysis you want

 It is very important to understand well that storing period and bringing soil to required storing temperature strictly depend upon the type of analysis and determinations required. For example:

1. Moisture determination do not allow any storing period

2. Nitrogen fraction determinations; NH4, No2 and NO3 allow very lesser period while total N can easily be determined in stored samples

3. If you want to determine total organic matter, you can determine in store soils but if you want to determine organic matter fractions, these may change even during storing

4. Biological analysis is very sensitive to storing and some of the microbes may dies during storing at low temperature or high temperature. So, please, allow minimum possible period of storing for such analysis.

To conclude, the researchers should be highly vigilant for soil samples storing that must be attached to the type of subsequent analysis required. 

Thanks everyone friends , do we have any standard protocol or any study highlighting the effect of long term storage o changes in n different soil properties?  . If we want to study the long term resilience of different soils , can we pick up a bunch of soil properties or single soil property to look at. ?. 

You welcome Dr Kumar. Here attached a paper in which you will find recommendations for soil sample storage (in pages 18-19). As it's obvious, it concerns only physical and chemical properties such as: pH, EC, TOM, NTK, P, K, Ca, Mg, S, Fe, Cu..trace elements...

Also, you can find a link to an interesting paper that you request the integral copy from the author here with us at RG.

Good luck

Khalid

Article Temporal changes in chemical properties of air-dried stored ...

Anoop Sir,

My answer is that soil properties do not change over a short period.  The pH will not change at all.  Unless salts are removed, the EC will also remain same. Only organic carbon, that to in air dried sample will under go very negligible change if kept under shade and cool condition.  Available P and K will also remain same. The physical properties do not change at all.  So, the soil samples can be kept for six months under shade safely.

However, I do not support keeping the soil for long time without analysing. It should be tested with in 3-5 days of its collection.

Maximum of how many years , we can keep soil  samples keeping their most of the properties unchanged .  Dont you think , during long storage , there will be a temporal  loss of organic matter of the  stored soils , thereby , affecting the aggregate stability , and thus leaving its cascading effect on different physico-chemical properties?.   

Yes sir,

on long storage it may happen.

Some of the  publication PDFs  enclosed by Khalid ( Thanks Khalid , wonderful ) was really an opener  . It was so  fascinating to read all of them . Many prospects for future emerge through these distinct headways on the subject . The storability of a soil depends on the type of the agro-ecosystem or the farming system or even the cropping pattern ?. The composition  of organic matter  and different  fractions of the soil N  ( Vulnerable to undergo frequent changes )  is another parameter that hugely decides the storability of soils under storage ?. Let us listen further from our colleagues.

Dr. Anoop, researchers have provided good elaboration of the question and a few references have also been added that will of great interest for those who are now actively involved in soil analysis, though we all should be benefited. An accurate and refined analysis is dependable for appropriate diagnosis of the problem.   

Thanks Dr Nazir and my other esteemed colleagues. All responses have been simply mind testing. And these answers prompted me further to let us know your thoughts about the salt affected soils vis-a-vis other arable soils. Do these two distinct soil types behave similar with respect to their storability and other consequent changes  . 

Yes Reyhaneh, It depends upon what determination you targeted.

That was the very purpose of floating this question . how long a  soil sample can be kept alive without changing the liveliness of the soil. no doubt , a lot will depend upon the  type of soil properties , we are looking at , and the type of land use , the soil samples come from , besides the soil buffering capacity , which is nothing but the entire functionality of soil in totality . Hope , Dr Nazir , Ms Reyhaneh and other esteemed colleagues will agree with me . 

Yes, Dr. Anoop Kumar, you just pooled up all the factors pointed out by different researchers. The importance lies in is that we should consider all these when storing samples. It may not be taken as granted that we can determine any soil property we want after any time of our convenience. It is not like that at all. Our diagnosis will depend upon life line of the soil, which should not pass in any way.  

Dr Nazir and esteemed colleagues,  why dont we have  such standard protocols for handling of soil  samples with various objectivity of analysis. One of the prime reasons , i think is the lack of standard  research-based information on these evasive issues of soil samples handling and their  storage.   

Dr Srivastava Sir, I want to know the effect of soil sampling storage on microbial biomass carbon, nitrogen and phosphorus especially. 

Dr Singh , this is very frequently asked question wherever soil sampling  and consequent analysis for different soil properties are involved.  It will be good if soil samples are dried in shade and analysis is performed as early as possible. but , for such microbial analysis , soil samples have to be stored for a much shorter period compared to  storage for conventional soil properties . Our esteemed colleagues have responded beautifully , you please go through  different responses, you will find some excellent answers.  

Yes, microbiological analysis and nutrient assessment should be perfprmed as soon as possible.

Thanks to everybody. The new challenge is to include these aspects into the soil testing KIT which several Companies are now pushing to farmer level.

Yes, You are right Zida.

The storage life of soil sample is dependent on the physical analysis or chemical analysis or biological analysis.

Yes, you said OK Sikha Deka.

I agree with you Dr Deka and Dr Nazir as well.  As early  as possible, we should analyse soil samples for biological properties , once you bring them to laboratory , and soil drying must be carried out in laboratory condition only . The reproducibility of the soil test results with regard to chemical properties depends upon the storage conditions , while not much of the changes , you can expect with regard to physical properties while storage , whether short term or long term..? 

Storage life of soil samples depends upon the kind of nutrients we are looking at. Like nitrogen will be most vulnerable while P and K least vulnerable. 

Well said Dr Shirgure..i agree with you..

As soon as possible solves all biases that the corresponding results might bear if the soil examination is targetting living organisms. However, depending on the analysis it could be preferred to wait and air-dry the soil samples.

I agreed with Shirgure, Storage life of soil samples depends upon the kind of nutrients we are looking at. Like nitrogen will be most vulnerable while P and K least vulnerable.

Respected researchers, especially for physico-chemical and micro analysis of 'treated' soils, i will be thankful to have some additional discussion and eye-opener references on: 1. How to store 'wet' and 'dry' soil samples (not loose, bound cylinders) from post-test period to analysis period , 2. What effects can various storage conditions have on physico-chemical properties and how, 3. Post-testing period, will the storage duration mean 'extended reaction periods' which normally seem to be unaccounted for, mostly?