To better understand why/when/where to apply fertilizer, you'd be better to read on what the individual elements... N..nitrogen, P. ..phosphurus.....and K..potossium (potash) does for plant life including lawns, trees, shrubs, annuals, perennials, and bulbs. In a few short words, nitrogen greens things up, makes them grow and can interact with how phosphurus works...which is usually to produce strong rooting and encourages flowering where applicable. Nitrogen can, however, cause the phosphurus to not produce flowering, the plant is being told to produce foliage at the expense of flowering. Potassium aids the plant to produce strong rooting and gives winter protection. Then the other elements kick in..zinc, molybedunum..(sp), copper, lead, etc, etc....you can read more about them in the fertilzier article. Far from not applying, nitrogen in spring advances the greening up and helps lawn grasses fill in bare spots; it promotes strong growth. Where flowering plants might be near such lawn, its best to hand spread the fertilizer so it doesn't act on the garden plants. This is not to say that fertilizer for flowering doesn't have nitrogen in it....it certainly does, but at a much reduce rate. Look at the famous brand of fertilizer for flowering...Miracle Gro...15/30/15...the phosphurus is much higher and promotes the flowering and rooting. Some people use the individual elements in their fertilizer...this is alright used for what they do...Ammonium nitrate has nothing but nitrogen...superphosphate, 0/20/0 and triple superphosphate 0/46/0 has nothing but phosphurus and potash fertilizer can also be bought in its only form too. To not apply fertilizer on a lawn is inviting poor growth, disease entry, and otherwise a lousy lawn. Some might suggest you apply nothing but organic matter....and that is fine, where such can be injected into the lawn and the time interval to wait for it to work. Organic fertilizer must work its way through the soil and be the stuff that the lawn needs...N, P, K...and trace elements... Inorganic fertilizer works immediately, over long periods of time and has the trace elements necessary for good soil health. Too much of any good thing however, can cause problems much the same as too much of the bad. Read articles on 'fertilizer'...and read further articles on "compost" and understand better the why's before the 'whens'.

I do not know about your area but thought i'd give you my opinion anyway! Your local extension office should be able to tell you the usual timing for applying crabgrass control. Then if you consider using the chemical Dithiopyr (one brand name is Dimension) timing is not as important. This product works over a longer time and will also kill small seedlings.

I was able to put down the pre-emergent but however messed up over a small section where I was supposed to apply 1/2 lb but applied 1.5 lb:(. Will it burn the grass? I had the numbers written for fertilization as well and applied that instead. Anyway here is a picture of what it looks inside. This is my first time applying pre-emergent but is it normal to look like this? It almost felt here and there like small sharp stones. I am just concerned whether I got a bad bag.

Herbicide Safety and Weed Control Comparison in Spring Seeded Kentucky Bluegrass "Early spring preemergence herbicides are often necessary in Indiana to prevent troublesome annual grassy weeds such as crabgrass and goosegrass. Additionally, these applications help to prevent the emergence of some broadleaf weeds. Most preemergence herbicides work to kill weeds by preventing cell division causing death to weed seedlings shortly after they germinate. All preemergence herbicides (except Tupersan) work to prevent the emergence of turfgrass seeds as well as weed seeds, so a turf manager cannot use a preemergence herbicide if they plan on seeding in the spring. As mentioned, Tupersan (siduron) may be used for preemergence control of annual grassy weeds in newly seeded cool-season turf. Another strategy is to use a postemergence herbicide instead of a preemergence herbicide to control crabgrass and other weeds in late May and June that is safe to use on seedling turf. Options include Drive XLR8 (quinclorac), Quicksilver (carfentrazone), Tenacity (mesotrione), and SquareOne (quinclorac + carfentrazone). These products can be most safely used very soon after seeding to control crabgrass (see label for exact details on each turf species). If the seedlings are more mature (have been mown 2-3 times following their emergence) then other products such as Q4 Plus (quinclorac + sulfentrazone + 2,4-D + dicamba), Onetime (quinclorac + MCPP + dicamba), or Solitare (quinclorac + sulfentrazone) can also be used. The objective of this experiment was to evaluate herbicides at three different application timings for use in establishing Kentucky bluegrass from seed in the spring."