"What about sunbathing?"
Well if he's sunbathing, it doesn't matter if he's a farmer or not. The only way a farmer, as a farmer, can make use of photons is to plant crops.
"But anyway: Imagine it was raining donuts and you sat on the ground and caught them as they fell from the sky (the origin is unknown). Now let's say someone taller than you came along and held a basket above you, thereby catching the newly falling donuts. You have the donuts you caught before, and he has the donuts he caught after placing his basket there. Do you have a rightful claim on his donuts purely because you caught the donuts that fell before them?"
I would probably say that the guy sitting there first has a better claim to the ones falling towards him than the tall guy. I don't spend too much time worrying about scenarios like this though. Perhaps a better question is who owns the land the guy is sitting on.
I just wanted to post this quote from Mr. Burns, I love it except for the appeal to nationalism/patriotism in the beginning:
"If you can take advantage of a situation in some way, it's your duty as an American to do it. Why should the race always be to the swift, or the Jumble to the quick-witted? Should they be allowed to win merely because of the gifts God gave them? Well I say, 'Cheating is the gift man gives himself.'"