I do not know the answer to that one but my guess is that the N fixing microbes (bacteria) feed on the humates that they are mixed with and this is why you would reapply the product every 6 weeks. Like I said I think the way to go will be adding the 1/8 lb of fert with every other application.
The price for the Sumagreen Turf is good and did great for me, my lawns and my bottom line. The guy told me yesterday that price was not changing this year so I actually raised my prices by a total of $1 per treatment on every client. That is a great increase in value to the business for me. Especially since I saved money on each lawn last year already.