for me, i found it alot easier to figure out what specific issues i had an then research what chemicals/fert i needed. personally it got way too confusing and complicated trying to learn all the different chemical's applications when I really only needed 3 or 4 for my specific turf issues.Cincinnati guy said:
if you are looking for clarification on which specific ferts to use a soil test would be beneficial. I used Waypoint analytical and they will tell you the exact N-P-K formulation for your fert.
https://www.turffiles.ncsu.edu/ is a good resource for identifying weeds/diseases, etc and recommendations for treating it.