After talking to people two years ago, I figure total system is a scam. No proof that any of the exhaust stays in the soil. As exhaust is mixed with total fan air and most of that is exhausted behind the shaft with any narrow opener how can the soil capture any amount of the exhaust. Also there is very little nitrates in old engines not counts all the new engines, how can you get 30-50lbs_acre reduction in N applied. At present I have seem no tests other that company or people paid by company there is anything in the system.