Would appreciate advice on fertilizing lawn. We have a large grass area with many weeds. I told my gardener no weed killer so he said he would like to at least use fertilizer to help the grass. The brand is Best and it is ammonium sulfate 21-0-0. They are small granules that look like salt. He says they will almost immediately dissolve when watered. I have 4 hens and they free range all day. They really aren’t on the grass all that much. I’d say 90% of their day is spent foraging under some brush I have on a small hill away from the grass, but they do have access to it and are on it sometimes. Thoughts?