The synthetic fertilizer needs to be compatible with the organic material you will be using. Just what to use depends on what you need to accomplish and that means you need to look at your soil. Rather than think of an organic "fertilizer", merely substituting that for synthetic, think in terms of feeding the soil (the Soil Food Web) that will feed your turf grass.
What is your soils pH?
How much organic matter is in your soil?
What kind of life is in that soil?
How well does that soil drain?
Do you mulch mow or pick up the grass clippings and throw out 1/2 of your lawns annual nutrient supply?
In addition to a periodic soil test for pH and nutrients perhaps these simple soil test will bne of some help.
1) Structure. From that soil sample put enough of the rest to make a 4 inch level in a clear 1 quart jar, with a tight fitting lid. Fill that jar with water and replace the lid, tightly. Shake the jar vigorously and then let it stand for 24 hours. Your soil will settle out according to soil particle size and weight. A good loam will have about 1-3/4 inch (about 45%) of sand on the bottom. about 1 inch (about 25%) of silt next, about 1 inch (25%) of clay above that, and about 1/4 inch (about 5%) of organic matter on the top.

2) Drainage. Dig a hole 1 foot square and 1 foot deep and fill that with water. After that water drains away refill the hole with more water and time how long it takes that to drain away. Anything less than 2 hours and your soil drains� too quickly and needs more organic matter to slow that drainage down. Anything over 6 hours and the soil drains too slowly and needs lots of organic matter to speed it up.

3) Tilth. Take a handful of your slightly damp soil and squeeze it tightly. When the pressure is released the soil should hold together in that clump, but when poked with a finger that clump should fall apart.

4) Smell. What does your soil smell like? A pleasant, rich earthy odor? Putrid, offensive, repugnant odor? The more organic matter in your soil the more active the soil bacteria will be and the nicer your soil will smell.

5) Life. How many earthworms per shovel full were there? 5 or more indicates a pretty healthy soil. Fewer than 5, according to the Natural Resources Conservation Service, indicates a soil that is not healthy.

-pH is currently on the lower side, 5.7 or so on average at this time.

-Organic matter is "medium high".

"What kind of life is in that soil?"

-I'm not seeing a huge number of worms, other than when there is rain.

-Soil us sandy loam; drainage isn�t an issue in this area of the yard.

"Do you mulch mow or pick up the grass clippings and throw out 1/2 of your lawns annual nutrient supply?"

-Mulch only.

3) It does fall apart.

4. It smells like dirt. Nothing odd.

Any other questions?

low worms could be due to the chemicals which have been used on the lawn in the past???

if you stay steady with a organic regimen, the worms'll return and will help make soil better.

Earthworm population is an indication of your Soil Food Web so low numbers of them indicates a low SFW. That might be due to the synthetic fertilizers, but most likely is due to low levels of organic matter in the soil which is what the SFW feeds on, but that soil pH may also contribute. Turf grasses prefer a soil pH in the 6.2 to 6.8 range.
A "medium high" notation about organic matter is about meaningless since that could be anywhere from 1 to 6 percent from most soil labs.

Great looking bit of lawn there! Good job. Whatever you're doing, it worked. Now for the long haul. If you want to cascade your inorganics and organics for a while you can try it, but you don't need to. See that band of brown stuff near the hardscape? That will be a problem in the future if it's under all of your lawn. Fortunately your varieties aren't big on producing too much of that stuff unless you use too much nitrogen. I'd pick up the clippings on that lawn except for a few times a year. It just looks too good to pollute with dead brown stuff. Now if you mow by the book you can leave the clippings. But almost nobody mows by the book. So use that good stuff somewhere else like around your shrubbery.

When you reach down and spread the grass apart, do you see dirt or a lot of that brown stuff? If you see a lot of that stuff, you'll be reseeding on a regular basis, the seed will grow in that stuff and die in that stuff. So every fall and spring, core aerate. That's all you need to do. Core it twice a year and you should be fine. Your grass is probably one that grows in any type of soil, no? One of those varieties that they sell in big box stores, right?? It looks so good right now, you just need to water it deeply once a week. If that isn't enough, then that stuff is blocking the water from getting into the soil at a proper rate. Coring will help that and take the nutrients down below the soil surface. Leave the grass clippings on the lawn for two mowings (a week) after aerating. Then water the dog out of it, a good deep water.

Most important for you is to cut it as often as it needs it. How often is that? If your grass there is 3-inches, which is what it looks like you're putting the mower on, and you've been using inorganic nitrogen, you'll probably need to mow it every third day because all three of those varieties will grow an inch that fast (unless they are specifically slow-growth hybrids). If you let it go to 5 inches and then cut it to 3 inches, you're going to wear out your grass and get a more of that brown stuff between the soil and grass. Most people do exactly that, then they nice looking lawn fails to sustain, and you end up starting all over again. But I can't imagine that happening in your zone with those varieties. Look at it this way, Yankee stadium puts perennial rye and bermuda grass on its field in Zone Bronx. They are specialty hybrids in a carefully controlled microenvironment. They meticulously use liquid fertilizers, organic, and they just mow the heck out of it and water deep when needed. You won't get a lawn like that with bluegrass, fescue and rye. Your grass will bunch up over time and form small lumps, which to me are not unattractive and are a sign of a healthy plant. You are lucky you can grow bluegrass and fescue in the same field though. Use organic (like blood meal or my favorite, cottonseed meal, good ol' smelly cottonseed meal) as soon as you can. Your biggest friend will be compost tea. Use it this coming spring.

Here is a link that might be useful: Core aerating a cool season lawn

Soil aeration and dethatching were developed by the companies and researchers that have promoted synthertic fertilizing over replenishing the soils organic matter because soils that are fertilized synthetically, and not properly, will develop both thatch and compacted soils over time. All of that then leads to sickly plants that are more attractive to insect pests and plant diseases that then require the application of poisons that also kill off the beneficial insects that could keep those insect pests and possibly plant diseases under control.
If adequate amounts of organic matter are put back into the soil then the Soil Food Web will help control thatch so dethatching becomes unnecessary and will work at creating pores in the soil so maching aeration is also unnecessary.
Someone starting with a sick soil that needs both aeration and dethatching may need to do that once, to get some of the organic matter into the soil, but once adequate amounts of organic matter is in that soil further aeration and dethatching will not be necessary. However, that thatch could also be a good food source for the SFW.

Yep, aeration and dethatching are excellent for the lawns, that's for certain. Fescue really likes a regular aeration in clay soils, especially if you aren't using a Brill or other manual lawnmower. The heavy equipment always compacts soils, and clay doesn't bounce back from that very fast. Not that that is all bad since moss grows really well on compacted clay, especially in the shade where you don't have a lot of wind. Speaking of which, aeration is absolutely necessary where you don't have good wind flow. It helps the air get to the soil level. Mostly fescue doesn't have a problem with thatch, though it can if it's really thick, very mature and has bluegrass and perennial rye mixed into it. In those cases you want to dethatch regularly. Dirt microbes are amazing things. They just bounce back from physical disruption so quickly and so well. Liquid dethatching is also excellent, but a little more expensive. It works by establishing microbes within the thatch itself, which is useful when the thatch is more than an inch thick. Microbes don't travel vertically toward the sun very much, so going top down is always a smart thing, especially late in the day. Common sense always prevails though. If you can see your dirt, you don't worry about thatch. And coring is so simple as to make it a no brainer when it comes to compacted soil. Add gypsum to clay soils after you core aerate and lime if you need it for fescue, bluegrass or rye (never lime Centipede though). If you don't have compacted soil, be happy!!

Here is a link that might be useful: That compacted stuff can make you ornery....

The only people that advocate the use of gypsum in most clay soils, or any soil, are those that wish to sell you something whether you really need it or not. Very few soil scientists would suggest using gypsum except in the western sodic clay soils to aid in moving the chemicals that accumulate in those soils due to low rainfall.
Only add lime if a good reliable soil test tells you lime, and which lime (Calcitic or Dolomitic), is needed and how much is needed.
Finding good information about liquid dethatchers is difficult but these rely on microbes, wee thingys that need air ie. aerobic bacteria, and being sealed up in a bottle for some time where air is not readily available can be very deterimental to their life. Most all the information I have found is from people that want to sell you this product, a not very good source of information, because no one with something to sell you will ever tell you their product does nothing for you.

It is true that gypsum often is "sold" as a magic soil amendment for clay soil, but that does not make it the wrong choice in many instances. Especially when you are planning on adding fescue. Gypsum is an excellent soil amendment, and there are many farmers that use it in clay pastures. I'll post just one well-known celebrity organic gardening advocate who understands the benefits of gypsum AND the hype. But don't anyone believe that no one advocates gypsum unless they're trying to sell it to you. Not true. I've had great results with it.

It is extremely hard to find good information about liquid dethatchers. Very true. You have to find what works for you by trying different things out. It's also hard to find viable mychorrizae, but it can be done, and it does wonders for compacted clay soils as it helps roots penetrate deeper. I use it with gypsum in some cases.

I wouldn't qualify as a salesman, so you now have two sources of reliable information that advocate the use of gypsum to break up crusty clay soil surfaces and to help cut into clay soil. You can use it at the bottom of a hole in clay soil to give roots that little extra oomph in growing quicker. I used it in the bottom of a 3-foot circular hole for a 2-year-old thuja green giant, which was planted next to a 3-year-old thuja. Worked lots of bark, leaf mold and humus into the hole and let God water it (it's away from the Hunter irrigation reach, long reach though it may be). This year, four years later, the 2-year-old (now 6) is higher than the 3-year-old (now 7) by a few inches. It simply MUST be the gypsum!! =) Well, it very well could be. But one never knows.

Here is a link that might be useful: A Celebrity Expert (not a salesman) Recommends Gypsum

Mr. Reeves does not recommend gypsum as you seem to think. He does tell you, if you read a bit further, that organic matter will do more for your soil than gypsum will. Perhaps the discussion linked below from someone with a phD will help.

Here is a link that might be useful: Gypsum and clay soils

Apparent misunderstanding of the English language on the part of the last post. Reeves recommends gypsum in the following paragraph and he also recommends organic in a noncompetitive manner as a great soil amendment, as of course it is. Thousands of academics recommend gypsum as do most of the farmers I've known with clay soil. In fact, all of them.

Walter Reeves explaining how gypsum helps:

"In fact, gypsum does soften soil to some extent. In particular, soils that form a crust after a hard rain can benefit from top dressing with gypsum. Seedlings will be better able to emerge without the hard crust to contend with. If you notice that vegetable seedlings seem to have a hard time pushing through your soil, adding gypsum at a rate of 5 pounds per 100 square feet may help."

And indeed it helps in even smaller amounts. Further, in yard lawns where there may be a history of inorganic fertilizer and salt byproducts in the ground, gypsum counteracts the damage quickly and is an awesome companion to organic matter spread on the lawn (like cottonseed meal or compost/compost tea). The link below was written by a guy with TWO phDs. So there. lol Good luck!

Here is a link that might be useful: Another soil expert recommendation for gypsum

I would hardly call what Mr. Reeves wrote there as a recommendation, more a well if you must you could use gypsum statement.

Organic fertilizers are commodities traded world wide based on supply and demand. When I first started doing this in 2002, a bag of ground corn cost $3. Last year a bag of corn cost $21. Alfalfa pellets cost $12 then and now. Thus, last year I went with alfalfa pellets as my primary fertilizer. Here is a picture illustrating the benefit of simply alfalfa on a lawn. The lawn is zoysia and the photo was posted by mrmumbles on the other lawn forum in June 2011.

{{gwi:79605}}

Note the improved color, density, and growth. The alfalfa pellets were applied in May. Grain type organic fertilizer takes 3 full weeks to show improvement. The application rate for your first app would be 10 pounds per 1,000 square feet. Subsequent apps can be 20, 30, or 40 pounds per 1,000. If you apply too much the first time, the soil microbes will not be able to process it and it will stink on you.

Since you are off to such a great start, I would like to suggest you keep it up. As motivation, here is a lawn pic from another lawn forum. This owner is meticulous about soil testing. He goes to great lengths to get his soil chemistry exactly right and then applies tons of organic fertilizer.

{{gwi:93032}}

That picture was taken in July of 2010 when everyone else's lawn was going dormant from the heat. He lives in eastern PA, by the way. Here is another pic of the same lawn in December.

Note his is the only lawn in the neighborhood which is not going dormant. I have another one from April of 2011 which shows the rest of the neighborhood as tan colored and his looks just like the one above. The secret is getting the soil exactly right based on annual soil testing...and then pouring on the organics.

You mentioned you fertilize with chemicals a few times per year. Unlike chemical ferts, with grain type organics you can apply any time of year, as often as you like, and nearly as much as you can afford. With organics more is better up to the point where you smother the lawn. With chemicals, just a little more or the wrong timing will kill the lawn.

If you want to start in the spring, find out when your last frost date is (county extension service should know). Then back up your calendar by 3 weeks. Apply the organic at 10 pounds per thou about 3 weeks prior to the last frost date. Don't worry about whether you get a frost after that. We're only talking about general timing. Then on Memorial Day, apply at 20 pounds per 1,000. Repeat on 4th of July. On Labor Day you can go back to chems or repeat the organic. Or both!

If you want to have the best lawn on the block and are willing to mow once a week and water when necessary (as often as weekly in the summer), please visit my member page and send me an email. I know some gurus who can help you out.

Dchall - i'm going to email you to see if you can give me some tips. (sorry for posting on your thread Lawn_hobby.

maureen

I had always been under the impression that Kelp was a key ingredient to a healthy organic lawn? is that part of your regiment ?

If you can apply kelp at a rate of 20 pounds per 1,000 square feet, then yes. Most people cannot afford that much kelp. Last price I saw was $50 for 50 pounds. At best kelp provides micronutrients.

At the spray level, I believe kelp is good to prevent plants from being attacked by insects. Spray the foliage of veggie plants with kelp. The kelp helps improve the health of the microbes living on the outside of the plants. Some time back it was shown that there are 20 layers of microbes living on the outside of plants - yes, exposed to sunlight.

My understanding in addition to microbes mentioned Kelp Seaweed is also ideal for root growth and helps to resist drought damage.

I've seen soluble kelp powder... that dilutes 1 oz. to 10 gal of water to apply to lawns as a liquid foliage spray. One pound of powder makes about 160 gal. RTU. I've read that Foliar application is the most efficient and effective method for kelp application, 8 to 20 times more effective when sprayed to the leaves then when broadcast on the soil.

Saw 1 pound as low as $29 w/ free shipping... Beats the cost of shipping 50 Lbs or 10Lb liquid gallon jugs

Here is a link that might be useful: soluble kelp powder 1 - 44 Lbs

If what you have fairly readily available is kelp that can be part of the needed organic matter in your soil, but we should all use what is readily available in our area. For me deciduous tree leaves are readily available in large quantities and mostly free so there is no reason for me to spend money purchasing kelp which would only reach me via non renewable resource methods.
Kelp is not going to be a magic elixar but can be part of all the other organic matter put into the soil.