Do this...

Watering: Deep and infrequent is the mantra for watering. This is for all turf grass all over the place. Deep means 1 inch all at one time. Put some cat food or tuna cans around the yard, and time how long it takes your sprinkler(s) to fill all the cans. Memorize that time. That will be the time you water from now on. My hose, sprinkler and water pressure takes 8 full hours to fill the cans. Your time will likely be less. I like gentle watering. As for watering frequency, that depends on the daytime air temperature. With temps in the 90s, deep water once per week. With temps in the 80s, deep water once every 2 weeks. With temps in the 70s, deep water once every 3 weeks. With temps below 70, deep water once a month. Note that you have to keep up with quickly changing temps in the spring and fall. This deep and infrequent schedule works in Phoenix and in Vermont, so it should work for you. The reason for deep and infrequent is to grow deeper, more drought resistant roots and to allow the soil to dry completely at the surface for several days before watering again. If it rains, reset your calendar to account for the rainfall.

Mulch mow at the mower's highest setting. If the temps get above 95 in the summer, let the grass grow up taller (don't mow as often).

Fertilize with Starter Fertilizer on Memorial Day, Labor Day, and Thanksgiving(ish). You might have to buy it now because it sells out, but wait to use it. You can also apply an organic fertilizer in addition. The two fertilizer types do not interact so this is a safe practice.

Too late for preemergent now. Spot spray the weeds in April with Weed-b-Gon or Weed-b-Gon Chickweed, Clover, and Oxalis Killer (or equiv). Give that 3 weeks to work before hitting them again. Some weeds seed quickly and will be missed with the first spray. You only need to moisten the leaves, not drench the soil.

By following this care you will get into practice for your new lawn this coming fall. Fall is the best time to reseed. Wait until the summer heat breaks in September to seed and then do it right away. Write back in and tell us the condition of the lawn to see how to proceed (full reno or just overseed).

It may not be too late for pre-emergent. I'm in Virginia and the forsythia are still blooming. Dimension (a common kind of pre-emergent) also has an effect on newly germinated crabgrass so it can be applied a bit past the optimal application time (when the forsythia bloom). Read the directions on whatever you use and plan for a duration so it won't interfere with an early September planting. Use a starter fertilizer when you fertilize. You are very low in phosphorus and starter fertilizer has a good amount of phosphorus. Next year do another soil test and see where you are on phosphorus. Do not use lime. When you cut grass, cut no more than 1/3 off at a time. Keep your blade sharp. You should cut the grass as high as possible (without it flopping over). Do you have irrigation? If not and you think you may start over this fall, you need to plan how you will water the seed (sprinklers, hoses, timer). You might want to do one section this year, another section next year. Grass seed needs to be watered lightly several times a day for a few weeks.

I looked on the University of Maryland Extension Service website...they listed UMASS-Amherst as a testing facility. I sent it to them in the fall of 2016.

I have applied nothing but the standard Scott's fertilizer for the Summer and Fall. (last June and September).

I was wondering if I should add organic matter now and let the nutrients have time to work themselves into the soil or just wait and do that when I seed?

Thanks!

Anytime is a good time to add organic matter. The easiest, most efficient way is to use what you have. Leave your grass c!Ippings on the lawn when you mow. When leaves fall, mow them into the lawn. Get leaves from your neighbors and mow them in too. Roots in the ground and an active soil life (bacteria, fungi, earthworms, etc.) add organic matter, so keep things growing.

That's a bit unfortunate. Of the choices UoM supplied, you got stuck with the poorest. Not your fault. You may have noticed that the UoM links to UMASS are dead and probably for good reason.

UMASS uses Modified Morgan, which was developed for the unique soils of the N.E., Maine Vermont, Mass etc. and isn't so useful for Maryland. It would appear that the Mehlich tests are the test of choice for Md. (it's actually becoming the universal test of choice for most regions)

http://mda.maryland.gov/resource_conservation/Documents/consultant_information/2006%20II-B%20p1-4%20s5.pdf

The issue is "how accurate are the Morgan tests are for your soil'?

That's indeterminate.

I'd suggest you follow the recommendations given for nitrogen and phosphorous this year and test next year with a new lab: Brookside. Spectrum or U of Del. and use the new test to balance your soil and correct deficiencies next year.

In the meantime follow the advice you've been given on OM and maintaining/improving the lawn. Spoon feed the recommended 2 pounds of phosphorous. Apply 1/2 bag rate of Scotts 24-25-4 starter fertilizer May 15 and again June 1. Apply 1/2 bag rate of the same product August 30 and again Sept 15. Otherwise follow a standard fertilizer schedule for Oct and Nov.

BTW, is your soil very sandy as indicated by the test?

When you say "spoon feed" do you mean I put my spreader on 1/2 the
recommended setting? Will that allow me to run back over it with the
second half two weeks later?

Basically, yes. The only wild card is whether or not the 1/2 setting will apply at half rate. By "spoon feeding," I do mean for you to split the bag up to allow for the second half of the bag to be applied two weeks later. This gives the grass an opportunity to have better access to the phosphorous before it gets tied up.

It's not a big deal if you don't do it.

Also, the "regular schedule" you mentioned- is there specific brand or ratio you recommend for late Fall?

That depends on the type of grass you have.

For KBG, that would include any type of High first number NPK October first and urea in late November.

Becky or jc411 have experience with cool season grasses in your "area" and can advise you.

The test might fairly accurately reflect your soil needs (or not). I've never seen any conversion factors correlating Morgan with other tests, so, I can't say. My best guess is probably not. Morgan was developed for the acidic, low CEC, cool and wetter season glacial till soils of the NE. On its face, your soil is reported as low CEC (but CEC is a calculation based on the results of the reported cations), the other traits of your soil aren't so similar. :/

Early October is a good time to fertilize cool season grass (KBG, fescue, rye) after a Labor Day fertilization. You can use any fertilizer that gives a good feeding of nitrogen. I would go with a slow release fertilizer or Milorganite, or maybe an organic feed (corn, soybean, alfalfa, etc) if you might like to try that out (and can find products at a reasonable price). Milorganite has a good amount of phosphorus, so you could also use that in late spring instead of starter fertilizer. After the grass has stopped growing (you have put the lawnmower away for the winter) and before the ground freezes, you can apply a quick release nitrogen fertilizer (like urea).