I have absolutely no legal training, but I landed in a ciruit court
judge's field once. He wasn't happy, but over time we managed to cool
off and talk about the particulars. Here's what came out of the
conversation:

When you land in a field, you are trespassing, and you should conduct
yourself as such.

The owner, can, in theory, order you off his property. If he forces
you to leave your sailplane behind, he becomes liable for its safe
keeping.

The law is your friend. If things get out of hand, recommend that he
call the authorities, or call them yourself. They don't want to do any
paperwork unless there is obvious damage. They will usually calm the
farmer down and expedite your retrieve.

Since you have already done damage to his property (by landing on it),
don't exacerbate the situation by causing more. Cutting a gate chain
or lock is tantamount to breaking into his place of work. How would
you feel if someone knocked down the door to your business, then put
up a new one with a note saying the key is in the mail? (I've faced
the same dilemma and chosen the path of breaking and entering. Just be
clear that there's NO justification for your actions, certainly not
from the point of view of the property owner. It is very possible you
may expose him to more financial risk by your actions than the value
of your $100K glider. You are jeopardizing his income for the sake of
your overpriced plastic toy.)

Never offer money to placate the farmer. Yes, it is convenient for
difusing an otherwise uncomfortable situation, but it sets an
undesirable precedent and puts both you and the farmer on questionable
legal ground. From your point of view, it is an admission of fault...
and who knows what fault the farmer may find after you leave. Don't
bring up the subject yourself. Let the farmer ask for money. Inform
him that you are insured for any damage you do and you are happy to
give him your insurance information. (We discussed whether asking for
money constituted running an unauthorized landing strip... I used this
notion once to answer such a demand. I then offered my insurance
information. It worked. The farmer wasn't happy, but at least he had
improved to "politely annoyed" by the time I left. He never followed
up with my insurance company.)

Reimbursing him for services offered is another matter entirely. If he
wants to use a tractor to fetch the glider, or prefers using his 4x4,
or wants one of his farmhands to oversee the retrieve, then it is OK
to offer a reasonable fee in exchange.

Never forget who the uninvited guest is. You've called him away from
his work. This has a measurable impact on his business. You may have
damaged his land, property, or livestock. You are, in his opinion, a
dilettante, serving no valuable function in the world. (If you don't
understand why, put yourself in his shoes, and get real.) Swallow the
farmer's antipathy with polite patience. After all, you deserve it.
And remember what your objective is: to get your glider home in one
piece... and hopefully leave an impression that will improve
conditions for the next sailplane pilot who lands there.