Maybe I should wait until next week, but I don't think that answers the question I have. Maybe my memory isn't clear, but except for Reardon's anniversary, I don't recall other specific dates having been mentioned. September 2nd is mentioned quite a bit, and I didn't even associate it with the "fertilizer," as you call it. I think there's more to it, but I don't know what it is.
ML/NJ
I believe the book begins on September 2. The book covers a period of 3 or 4 years, and that date gets mentioned every time it comes up in order to measure the passage of time.
Next week that date becomes very significant and memorable.