Simply Organic Lawn Food
This is a no phosphorus organic lawn food that is a good alternative to Milorganite. Milorganite does not contain potassium and it’s an important macronutrient to apply so I would rotate in a product like this in your program if you want to stay organic based.
Related products
Milorganite
For years Milorganite was part of my lawn program and is also a perfect fertilizer for beginners who want to start using granular but need practice with using a spreader without fear of damaging the lawn. My soil tests have since told me that I need other products instead of milorganite (it is high in phosphorus) but using this a few times a year and mixing in a product with potassium for the rest of your apps would be a good plan.
p.s. look for this locally or for "clones" of similar products that will usually be called some sort of "organic lawn food" where you'll get a cheaper price than buying online
Turf Builder
You've probably seen this at every big box store in the country. For someone just getting into fertilizer who wants a tried and true option this will work well and has settings right on the bag for Scotts spreaders.
Starter Fertilizer
Starter Fertilizer is always part of my seeding and overseeding projects. Recommended rate is 3 pounds/1000 sq ft and at that rate this bag will cover 15k square feet.