but in this page here the farmer has his legs up in a way that makes me think he is the uke
http://www.mangago.me/read-manga/koi_saku_potager/nmt/v01/c003/pg-33/
I thought it wa pretty obvious yui was the seme... I mean he pushed the guy down after saying "I want to put it in" and that's a semes line. If an uke said it they'd be like "I want you" or "hurry and put it in" yui was more like asking if it was okay while stating what he wanted to do... and sorry but setsu isn't assertive enough to be seme LOL
it's really vague who is seme here. both chapters don't clearly show. Although yui is assertive, some of the panels are confusing. On second read i interpretted it was the farmer.
Also when are we having miki side of the story? *-* we need that. He's really cute. Especially the ending panel of 2nd chapter.