Cost of Crop damage from glider landing in farmer's field?

There are criminal, civil and practical aspects to this question.

Criminal: In most states, you are trespassing when you enter another's land without permission, or if you have been put on notice (by a sign, etc) that entry is forbidden. Usually there is an "emergency" defense to trespassing (and most other crimes), and having your glider fall out of the sky should count.

Civil: If you have damaged the crops, or any other property, you are civilly liable for their value, because it is foreseeable when you take off in a glider that you might land out. Specific laws are going to vary from state to state, but the landowner should not have the right to confiscate any of your property, or have a lien.

Practical considerations: If you run into an angry person, just leave. You don't want to be accused of assault or breach of peace by getting into an argument. If someone tries to detain you somehow, ask them to call law enforcement. If law enforcement wants to arrest you, go peacefully. The time and place for arguments is in the courtroom.

Of course, having any problems at all is very, very unlikely.