I'm only a homeowner so i can only provide what i read off ICT website. I just purchased some of ICT's products. I did go to Bill's site and according to ICT's website NPP can be applied in late spring as a preventive and as needed in the summer. I printed off the 2011 Organic Turf program pdf. This file gives timeframes and amounts to use. If you email Bill from the ICT contact page, he most likely will get back to you pretty soon. I think he's busy this time of year, but he responded to my emails pretty quick.