(Note that I'm learning Hebrew, but have read this question asked in the discussions and this has been answered by native speakers).
Khakla'í is the more recent one. It means farmer (Or farming/things related to agriculture).
The other, ikár, means farmer or peasant, it's dated, and it's originally from the Akkadian language. You can use them interchangeably.
(For the exact answer, search the Hebrew discussions for the word peasant. You can find the discussions on Duolingo.com when the website is in desktop view/mode. You don't need to be on a computer to see this, you can switch most browsers to this setting. Occasionally it will be listed in the settings as IA. If you need help, just ask)
3 March 2019