The real estate agents operate as a cartel and wouldn’t accept offers this way.
The auctioneer is typically a licensed real estate agent. The whole farm will be sold that day, sometimes field by field, sometimes as a whole (sometimes both ways - this is complex to understand: they get bids an all fields separately, then for the whole and the larger total wins). Then they sell the equipment and junk. Bankers are on hand to verify financing... For houses most people wouldn't work this way, but for farms it makes sense.
I have no idea why there are regional differences, but I'm not really surprised they exist.
I'm sure it is multi-faceted, but supply management is a big difference. Notably, diary farmers in some provinces voted to impose a quota price limit in an attempt to make it affordable for new farmers back in the mid-2000s. This means that the amount that quota sells for is the same now as back then, even though the fair market value has at least doubled in the meantime.
This has created a market aberration where the quota is undervalued and to resolve it farmers have started tacking the difference onto the purchase of land. In other words, on paper I pay you $x for quota and $y for land in order to stay compliant, even though in reality I'm actually paying you $2x for quota and $y-x for the land.
This, of course, has driven up the price of farmland to unreasonable heights as people notice what farmland is selling for on record. $40,000 per acre isn't unheard of these days. I bet you in Iowa, despite having a climate that can easily outgrow us in Canada, won't see anything close to that.
As farmland prices have risen (up ~700% since 2007), residential sprawl out into that farmland has become much more expensive. This has increased the pressure on housing in existing urban areas, pushing prices up there. And, thus, the Canadian housing problem that's being discussed in the larger scope here.
For those who don't know, the best farmland in Iowa can go for just over $20k, and as you say can grow more value than anything in Canada. Iowa should be the most valuable cropland in the world - great soil, good climate, great national economy, and relatively flat land. (there are places better in some of the above, but they are lacking in at least one significant way and so the value of their land should be less today.)
It's certainly the case that the agent who knows that a particular bidder is the highest/most attractive offer is working for the seller.
You can have an agent working on behalf of the buyer, but my experience is that’s a minority rather than majority arrangement.
Dual representation can work out ok in some scenarios, but the hyper-inflated and super competitive market we're in right now isn't one of them.
If you tell "your" agent that you'd like to bid $1M but are able to and would pay up to $1.2M because you really love the house, you're giving away a lot of information that I decided I wasn't willing to give up and so kept all Realtors at arms-length.
The study determined that when a house was the property of the estate agent sold in a little more time at a noticeably higher price.
The idea if that your house sells (today) for (say) 100,000 units of value (pounds/dollars/whatever) the estate agent will get (still say) 5% of it, i.e. 5,000 "units" (also today).
If in a few more months time you can sell it for 120,000, the agent will get (a few months later) 1,000 "units" more, but he/she will have spent a lot more time visiting the property with prospective buyers, runnning ads on newspapers, whatever, so the incentive for the agent is to conclude the sale as soon as possible, even if at a (reasonably) lower price.
The proposal to correct the incentves was to have a flat percentage (like the mentioned 5%) until a certain amount and a much higher percentage (like - if I recall correctly 15% or maybe 20%) on the excess.
Of course it depends on the local current market, but estate agents have interest to push house price higher only until the property is an "easy sale", the sheer moment the house stays on the market for some time (this highly depends on the local market, it could be weeks or months) they will start saying something "Hmmm, maybe we valued a little too much, we (that means you) should discount it by 10%", this in the same 100,000 unit house means that you will get 10,000 unit less, while the agent would get 4,500 units instead of 5,000.