Here in Ibaraki I believe you can't buy farmland that is smaller than 4000m2. Of course you have to meet many other requirements as well.
I've been watching real estate listings for a year and I don't think I've ever seen a plot of farmland bigger than 3000m2. Is there any way for a new farmer to buy smaller plots?
We have bought several small farm plots less than 200m^2 each. Actually I guess they aren't technically ours yet, we are still working on the farming association paperwork...
But it is possible here in Nara to buy any size lot. The farming association must approve the sale, which is no big deal here in our small town. But if there is a lot of agricultural competition in your area, or if you are looking at a plot next to a commercial farmer, you may get some push back.
I would imagine that smaller plots wouldn't be listed with real estate agents due to their small potential commission and a belief that no one would be interested.
We asked around town and many owners were happy to sell and surprised that we would want their derelict plots. You may have better luck asking around your neighborhood, asking the farming association directly or asking the town office. If there is an unkempt lot in your neighborhood, the owner would likely sell. Your neighborhood leader would know whose land it is and may be able to contact them for you.
You also might consider buying a cheap tear-down akiya that has farm plots included.
I’ve heard Ibaraki are reducing the requirement to 2000m2 in the near future, whenever that is. I’ve looked into it too but it seems there’s no way to buy less than the minimum at the moment. We want to buy the abandoned farm plots surrounding our house - I’m going to try more seriously once we finish the house (if we have some money left over).