The soil you use to prepare beds and turf areas is more vaulable than a lifetime of fertilzer after the fact.  Mixing compost into your topsoil is the best way to add OM and encourage healthy root growth. The first and second week of September is ideal time for cool season grass like fescue.  Here’s a picture of a lawn in the spring that we aerated, overseeded, and spread 2-4-3 poultry castings.  All fertilization is 100% ORGANIC WITH DHS ENHANCED COMPOST TEA.