I was at my neighbours last week and he showed me this weird circle on his grass. He didn't have a clue as to how it got there. I asked him if his septic take was under it. Not! He's lived there for 33 years and doesn't have a clue. My only other thought is that perhaps he may have spilled some fertilizer on the ground in winter and it spred out on the snow and fell through when the snow melted. Any clues as to what this can be?