Basement floor drain flooding

We have an older ranch style farm house with a basement. the basement is about 6 feet deep, and there is an old 4 inch clay tile floor drain in the corner. It ties into a maze of field tile right under corn / bean fields right next to our house and have no idea where it goes or how to fix it. We have no sump pump system.

At one point, it was the only drain in the house except for the septic tank. Only the toilet went into the septic. Everything else dumped into this floor drain.

About 4 years ago our basement flooded up through the drain. Water was coming through it with quite a bit of pressure and we had to put a sump pump down there to pump it out. There is no pit so we just put the pump on the ground to get most of the water out.

Last year we re routed all of the drains to use the septic, so we could get rid of the drain. I just dont know how to go about it, or if it will cause problems trying to plug it.

Luckily, the septic system is working good and we know where the tank is if it needs to be emptied.

I am open to any suggestions, and money is very tight...

P.S. - our house is on a hill, and has decent slope away from the house. The basement drain is the only way the water is coming in.

Is this a constant flow coming into the basement of intermittent?
Going to presume you have well water.
Field tiles?? I have no idea what that is
This drain in basement at one time was for gray water to help irrigate the fields? What other source of water is used to irrigate the fields?
Could it be a broken water line to the house. Eliminate all possible sources.

It happens when we get a really heavy rain. and usually lasts for about a week after.

I live in the middle of nowhere, Iowa. Surrounded by corn fields.

We have rural water, which is city water piped in to rural areas.

Field tiles are clay tiles run underneath the cornfields to drain water from the soil during heavy rain.

The problem is, there is such a huge maze of tile under the fields, I have no idea where it goes or where it could be blocked.

The drain actually works great most of the time, but i'm thinking that when it rains heavily, it raises the water table up above the floor of my basement and that's when the flooding starts.

I guess my main question is, I would like to totally get rid of this drain, I just don't know how to do it and am worried about the pressure under it if I do cap it.

I'm thinking about just filling it with concrete.