If you are popping wheats then silver can't be far behind. Once I hunted a spot where I popped a large cent, a canadian half dime, and a few indians and barber dimes from memory or so. It was wierd as it was a narrow strip of the grass in the middle of the field where they all came from. As I was leaving, a guy who works for the parks mentioned they had filled some ruts in the field a while back. That must have been where these coins came from, as they were all in one about 5 foot wide area about 20 feet long or so, but the grass had grown so I didn't know there was fill there. A lot of times when they build a home or such they strip the top soil and that gets re-sold, and then they use the dirt from the foundation to bring the ground they stripped back up to the level they want. They do that because they can get top dollar for topsoil, while the clay dirt from the foundation and such isn't worth as much to re-sell. Keep working that area as they bring in more dirt as you don't know what you might get. Why are the filling that site anyway?
There was a mowed grass lot next to some railroad tracks where my friends had pulled a bunch of silver and some of it pretty old from the 1800's. The soil had a lot of hot rocks and black sand and iron in it. I went there a few times with my friend but we never got any more silver out of there. Then one day I drove by and they had stripped about 12" of the soil out. We hunted it that night and got indians, barbers, and such. Some of which were right on top of this clay sublayer that was left when they removed the top soil above it. Just goes to show that no place is ever really hunted out. Those coins were all hidden by depth or masking or such. Bad news is all the good top soil was taken away and we never found out where. I bet it was loaded with silver.