I think you might want to focus the some major elements (e.g. C, N) in the soils to support the growth of the plants using some isotope geochemical techniques, also consider to other elements whose abundance, minerology, and speciation can reflect the human activity.

Supplementary to what to Dr. Ma's suggestion, it will be very interesting to know the free radical content of those soil samples you have. This free radical content may indicate the degree of humification of the soil that underwent through to which may correlate to the organic compounds that are/was present. You can do this If you have any possible access to Electron Paramagnetic Resonance (EPR) Spectroscopy or sometimes called Electron Spin Resonance (ESR) Spectroscopy.

I think you may like to do C and N-isotope measurements of soil organic matter, which provide information on type of crop.

May be good to check delta13C isotope composition of soil organic matter to know the type of agricultural produces in those ancient farmlands.

What about phytolith analysis?

Phytolith analysis has a variety of capacities to generate information pertaining to soil characteristics. Depending on the question asked, phytolith study can be quantitative e.g., pounds/kilos per acre/hectare of biogenic silica; or chemical/spectrographic; e.g. trace element analysis; or taxonomic, i.e. assignment to particles to taxonomic categories of plants, etc. Attempts have been made to use occluded carbon trapped in phytoliths for radiocarbon dating -- successes have been reported going back many years; and for recovery of DNA -- for which I know of no successful reports to date.

I have addressed the taxonomic problem for more than 4 decades and am sorely disappointed at the lack of progress. Phytolith taxonomy is a unique and complex system. Far too many current studies treat phytoliths like pollen, for example, which is wholly inappropriate. Apart from being "botanical" and "microscopic", the differences are many and profound. Many others are still at the level of the "grass taxonomy" presented by Twiss, Suess and Smith, 1969 which can be found in even earlier work, e.g, by Henri Prat in the 1930's or A. Grob in the 1890's. In fact, Erwin Suess tested an analytical method to distinguish grass phytolith taxa which he concluded was wholly unreliable. In recent years, the same method (possibly through independent invention) has appeared frequently in erroneous reports of taxonomic success and their flaws are readily evident. In one prominent case, reports of a method of high resolution phytolith taxonomic identification in the grass family, was repudiated by the authors who nevertheless proceeded to use their failed method to create a false history of agriculture using fossil phytoliths for some two decades to wide acclaim by the scientific community at large.

After 40 years, I ask the same question, "What about phytolith analysis." There is very little in my answer currently, that I can point to with much satisfaction.

Hi everyone, and thanks for the responses! Here's a little more information:

Several of the above suggested techniques appear aimed at revealing evidence of actual past human habitation/use; i.e., what crops were being grown. I am actually less interested in this aspect: my primary aim is to develop datasets of soil characteristics which may have influenced what land would have been useful for varying land uses between 8000-2000 years BP. These soil characteristics will be compared to existing archaeological data to explore the factors responsible for shaping human spatial distribution over archaeological time.

I am therefore looking for soil characteristics which would have influenced land use between 8000-2000BP, but that will still be present in a relatively undisturbed form in modern soil samples. Some soil chemistry may be of use, but others I anticipate will only provide an insight into modern agricultural practises (i.e. soil phosphorus is unlikely to represent conditions which were present when the region was in a un-modified state).

Any insights/suggestions/recommended sources for this conundrum would be greatly appreciated!

Hi Robbi ,Although XRF is widely used in geochemistry I suggest you ICP-MS and ICP-OES soil analysis, the multicapabilities of those instruments give you interesting qualitative and quantitative results for many chemical elments . May this article can answer to some your questions.

Article Anthropogenic units fingerprinted by REE in archaeological s...

Let’s see, sorry if my English is a little rough. I am working on your subject but in northwest Argentina. We took into account these soil geochemical evidences linked with plant production. So, we took several AVAILABLE content of some major and minor plant nutrients, available phosphates, manganese, copper, iron, calcium. Organic matter percentage of course also but the results were not as useful as we thought. You can see one of our papers at Quaternary Research. In other hand, as you probably know the most "popular" cultivated plants of each time and their nutritional requirements you can try to ensure that you are taking the needed elements in plant available way in soils. Another problem is present contamination with agrochemicals. For this point we took samples in abandoned agricultural fields. Another important point is to know very well the agricultural soil surface if you are lucky enough to have buried horizons, so you need very accurate soil descriptions. Among physical features you must have a good idea of soil compaction, normally agricultural practices produces porosity loss. Well you can ask me more if you need or want. GOOD LUCK! Is an amazing subject!

Seems like you are actually asking how did people choose 'settlement' sites 2000-8000 years ago, with the assumption that such selection would have been based on a cultural dependence on sedentary agriculture. First, regarding the assumption, it would seem necessary to consider that what folks thought was important to selecting a settlement site 8000 years ago could be very different from what folks thought 2000 years ago. In my own experience, folks with no technical soils training, but strong agricultural heritage can display a considerable skill at selecting productive soils (in these modern times, to purchase and "settle" on) where the underlying productivity is not apparent through routine soil analytical procedures. At what point such soil diagnostic skills may have developed is not at all clear to me, but as more historical and archeological evidence accumulates it seems clear that our ancestors possessed the same fundamental observation-association-application skills we do today.

On the few occasions I have had to see such effective, but no-tech soil selection capabilities applied, they resolved to mineralogy as a main, underlying fundamental characteristic. One must then bear in mind that mineralogy, and its impacts on soil properties and, hence, sustainable productivity at a given land site, are nearly entirely dependent on an adequate water supply. Besides, in those times, any settlement would have had to have convenient access to adequate water for direct human and animal consumption, not to mention the added transportation convenience of waterways. Interestingly, and perhaps mineralogically related, the mineralogy of interest in my observations were illitic clays. Illitic clays appear to be capable of providing a long-term indigenous source of ammonium-N and/or potassium. Admittedly not at levels we consider near appropriate for modern agricultural practices, but likely levels of considerable importance to the agriculture of 2000-8000 years ago.

Clearly other mineralogies could be important with respect to organic matter stabilization, ion exchange capacity, etc., but few of those would typically bear enough nutrients on-board to sustain a productive agriculture for much more than one generation. Additionally illites can undergo relatively rapid ammonium/potassium "recharge" under conditions of seasonal flooding, animal manure application/rotational grazing, etc. Come to think of it, there are a couple presumptive diagnostic properties of illitic clay soils that can be observed in the field with nothing more than a vessel, a stirring utensil and some water, but I have to assume that such observational awareness would have been much more likely 2000 than 8000 years ago -- which would seem to take you back to where I started.

Also, illitic soils seem to not respond well (plow soles, compaction) to mechanical cultivation in the modern sense, but apparently adequately well to the forces and dynamics involved in animal draft or human labor agricultural activities.

Would have to put some considerable thought into it, but one might be able to look at the illites themselves, and perhaps associated minerals, as a diagnostic for previous human agricultural utilization. Might even be able to derive some other information from alteration of typical illite particle size, and "fixed" ammonium/potassium content in suspected agricultural horizons compared to immediately underlying undisturbed horizons.

You have chosen a fascinating question. Good luck. Let us know how you get along on this one.

Hopefully preceding is of some use in your effort.

In that case..may be good to check the presence of soils typical of river-delta. Most of the past human settlements were concentrated along the banks of rivers and they appear to have utilized the proximity of water and fertile delta-soil for developing settlements. In my opinion the mineralogy of soils and carbon-isotope chemistry of soil organic matter would help to identify delta soil that was used as farm land.

Virupaxa's comments are on point. It occurred to me after my previous answer, that it may be possible to combine mineralogy (ag vs. underlying/overlying non-ag horizons) with N (illite fixed ammonium) and C (organic matter) isotopic data to get some kind of a handle on when and what was going on, then perhaps get at why (from perspective of folks in those times).

A caution on interpreting too much from C isotopic data. Though there seems to be some changes underway, there has been a long-standing general assumption that organic matter is relatively stable and that C-dating is therefore reliable. My work has indicated, and I apologize none has been published except in my original MS thesis and PhD dissertation, that organic matter stability is actually quite dynamic, with most organic matter being very labile when exposed to underground plant activity whether agricultural or not. In fact, exposure to an active microbiota in the presence of appropriate other substrates can result in remarkable levels of alteration of organic matter that has traditionally been assumed to be stable. My point here is, use considerable caution when interpreting organic matter C isotope data if the profile indicates any periods of substantial biological soil activity, whether agricultural or natural, after agricultural utilization ended. The difficulty this presents is further complicated by the structural status and mineralogy of the soil, which are also impacted by ag vs. natural plant activity. In general, natural vegetation promotes better structure and increased organic matter dynamics, while agriculture tends to burn OM down to its most stable components and substitute, in effect, highly comminuted (microscopic particles), minimally decomposed plant residues. That may be a useful soil diagnostic in some fashion for your purposes. As the amount of those minimally decomposed residues increases, crop yields drop, no matter how favorable the visual and physical appearance of the soil may seem -- unless, of course, there is access to substantial amounts of nutrients from an external source. Fixed ammonium in illites can apparently serve such a nutrient-source role, but those too will eventually deplete. Under agricultural conditions of 2000-8000 years ago, an illitic soil site would presumably sustain productive sedentary agriculture longer than a similar site without a substantial illitic mineralogy.

Which raises another interesting point with regard to your question. I recall that a satisfying (for a soil scientist anyway) explanation of the westward expansion of the original European colonies in the North America (U.S.) was depletion of soils. The mostly upland forest soils along the eastern coast were apparently good for about 20 years of productive farming, at which point they would be abandoned with an associated move westward to a new site with still undisturbed soils. As I recall the standard was when the tree stumps left from clearing the forest were gone from the farm fields, it was time to move on. Illitic soils would probably allow some greater or lesser extension of that kind of time frame, depending on flood cycles, animal management or other factors that might have provided some nutrient recharge of the illites (and organic matter level recovery). In the end, however, even those soils would almost certainly eventually be depleted to the point crop yields became too low to sustain the culture/community.

Hi

I think all the above answer are very good. In my country we have this tool and EDS and I prefer the second for elemental analysis. I would like to know if you have samples of seeds in this sites?

Hi Robbi,

My research group is recently submiting an international article about the forcing factors for the increasing of sediment fluxes in basin areas in the last 5000y.

Should you be interested I could send you a previous version about it.

Best of luck for your investigations

Cheers

JAG