He told the Omaha World-Herald: "I didn't know what to do. I was afraid it was going to suck me in more. I about gave up and let it do what it was going to do.
"It's hard to describe. You want to survive and you do what you need to do to survive, I guess."
Kaser said he cut through up to 2.5cm of muscle and nerves below his knee to free himself.
He added: "The bone stuck out down to my ankle. That's what I was hanging onto as I was trying to get myself out."
The farmer had become trapped in an auger, a tube that uses a rotating shaft to suck grain.
He did not have his phone and there was no one around to help.
Kaser was later released from a rehabilitation centre and will have to wait for the amputated leg to fully heal before he is fitted with a prosthetic leg.
He said: "I was in a hurry and didn't pay attention. Farmers, we're all guilty of it but we don't stop and think. We get in too big a hurry.
"Everybody says 'You seem so upbeat about it'. I know I will be walking again fairly normally. Other people can't, won't ever."