Correct, about 330M acres of farmland. Lol, I wouldn't call all 330M prime. Maybe 180-200M are 'prime'. The North Dakota, South Dakota, Kansas acres aren't going to win many 'prime' contests. They can produce a profit, yes. But no always a big one

You sure about those examples? I just pulled up the USDA soil survey of some place I've never been, Edmunds County S.D., and it looks to me like over one third of the county is capability class 2 or better, which is considered "prime farmland" or better.

Capability doesn't take into account climate or access to water.

I don't believe that is correct. This classification system considers both. To be in class I or II you need either no or "slight climatic limitations". I found another document that says N.D. has 47% of its area as either classes I or II, making it the third-most-arable state after Iowa and Illinois.

And how many people own as much (or same order of magnitude) as the gates ?

Unclear from my 5 minutes of internet research.

The #5 on their list of farmland owners (the infographic at the top of the page) has ~60% the farmland of the Gates family.

It's also worth noting that #2-5 rank 81, 81, 94, and 99 on the overall 2020 Land Report 100 -- and Gates doesn't rank at all. So a lot of people own a lot more land, but almost no one owns nearly as much farmland in the US.

[1] https://landreport.com/americas-100-largest-landowners/

thanks