the correct conjunction is "which"
Answer:
A comma after "environmentalism"
Explanation:
Because the comma would provide a proper clause
American Farmland trust work to protect the soil and keep it healthy as part of our holistic approach to keeping the nation's farm and ranch land productive for all and it educates Farmers on important conservation measures like cover crops.
"Keep," this is because the adverb always modifies the verb, and a verb is a action, and keeping is an action.
