The day started with a recce on the Roman denarii hoard site (JHF1) we discovered last December. This was to be an experiment to support our theory that a field has to be covered efficiently resulting in virtually no other items being recovered until the next ploughing session.
This was a wheat stubble field that was now more compacted than it was earlier this year. The field was covered almost 100% bar one edge on the last visit, we had to abandon the survey due to the wet weather that blighted the end of last year. The actual hoard site was covered intensively four times at alter intervals with no further finds.
On this visit we only recovered two items, a copper alloy vessica seal and a hammered penny of Edward I. This was in the the small area not covered properly (<100%) in the previous survey due to the wet conditions.
Our suspicions had been quantified.
This was the FIFTH time that we'd detected an area and encountered the "detection saturation point" resulting in minimal or no finds.
This proves conclusively that if an area is covered 100% there is little likelihood of anything further being found until the next ploughing event.
Our first encounter of "detection saturation" was at a new permission that the farmer had warned us that we'd find very little because it had been detected for 20 years. Of course, bravado kicked in and we decided that we'd find the stuff everyone else had missed. Wrong! We only recovered 2 tiny grots after 18 man hours!
The second instance was at one of our best Roman sites (TS1) where we'd recovered hundreds of Roman coins and several brooches.
We surveyed the site when freshly drilled and had great results. We returned at harvest that year and found nothing in the stubble!
The third instance was at another great Roman site that has produced several coins, brooches and a gold stater.
We visited the site when re-ploughed this Spring..... again nothing!
The fourth instance were the visits to (JHF1) the Roman denarii hoard field.
As mentioned, only two items were recovered from the area we didn't cover 100% because of the severely wet conditions.
We'd GPS'd the hoard spot and Rob drove the support vehicle over the area several times to flatten the stubble. This made it a lot easier to detect ensuring the coils were next to the field surface.
So there we were, on the hoard spot for the fifth time with the stubble flattened over a large area within the site. Nothing!
We had a chat with the landowner to report on our "experiment" and he was assured with the fact that once we'd surveyed, little else would be detectable. This assured him that "nighthawkers" would soon get fed up going on his land and finding nothing after our efforts.
We encountered the fifth instance when drove over to a permission (ETF) that has produced a prolific amount of fantastic Medieval finds and coinage.
We'd already surveyed there this time last year and found..... nothing! And that was three of us using the search techniques that have proved so successful over the last three years.
Once again we didn't recover anything and I said to Rob that it can't have been ploughed for the last two years! Seconds after that Rob found the coil cover I lost last year (in perfect condition) proving that it hadn't been ploughed at all.
A short time later the landowner appeared and we remarked on the lack of finds and that it can't have been ploughed for a while. He smiled and said it hadn't been ploughed since 2013!!! He did add that he was ploughing it in two weeks time.
Watch this space as it should show the difference between a field that has been ploughed and one that hasn't been ploughed for a couple of years.
So, there you go, if you cover a field 100% (the detection saturation point) you'll not find much until it is re-ploughed.
As you may have read a while ago we wrote an article on the virtues of covering a field 100% versus a random search resulting in less than 100% coverage. If you cover a field randomly you will recover finds on every visit..... until they run out.
Yes, there are only a FINITE amount of finds in a field, if there are 10 hammered in that field and you have found 10 hammered you will NOT find anymore.
It may take twenty years to recover those ten hammered coins due to differing plough depths and all the other factors that can influence your recovery rate. If you randomly search that field it may take a lifetime to recover those 10 hammered coins!
We accept that some of our "best" permissions WILL become virtually sterile after a few years using our search techniques. As a permission becomes sterile we'll hopefully replace it with a new one that may equal what the "best" sites produced previously.
We will be revisiting the denarii hoard site (JHF1) when it's ploughed in two weeks' time, again we'll report back on the difference between our last visit (searched three times intensively with no finds) and the next one.
So that's two sites in the next two to three weeks that we'll report back on to see what difference a ploughing session makes.
Meanwhile, we hope to see some of you guys at the XP Rally this coming weekend. It will be great to exchange views and experiences.