The general consensus is that worms are a good thing.

If the screwdriver is hard to push in, that means the soil is at least not soft enough to push a screw driver deep into. Could be rocks and could be friction. Or it could be the soil is relatively "hard."

How often do you water and for how long?
Where do you live?
What kind of grass are you growing?

Hey dchall, this is me... I used to bother you via email ;)

I have stopped watering and waiting for the grass to tell me when to water. The only watering lawn had was from the rain. And curiously, the rain was deep and infrequent!! hehe

WBG hose end application working nicely. Clovers are mostly gone. But I have these small light green/yellow grass which produce seeds above 2.5inch so I have to mow around there to control them. I guess it is one of those annual grass weeds.

Would deep and infrequent watering help in keeping away grubs and fungi?

I find that I can aerate using the 3inch flathead much faster than manual foot aerator and I am not removing the soil. I just did it in the problem areas. Will wait to see results before continuing.

dchall, I should have added that the place I saw earthworms was where I applied the diluted milk!

Earthworms live on organic matter, so the presence of earthworms in a soil is an indication that there is organic matter in that soil since they would not be in a soil that lacks OM. The presence of earthworms also indicates that other members of the Soil Food Web are present and that is an indication of a healthy soil.
The ease with which your screwdriver entered your soil is also an indication of how healthy your soil is, but that you encounter problems about 3 inches down means that you probably need more organic matter in the soil.
A good, healthy soil will not need aeration since the adequate amount of organic matter in that good, healthy soil will provide the space between soil particles necessary for air infiltration.

On other forums there is some discussion about the use of the liquid "aerators" called Aerify and Nitron. Generally they seem to work when used frequently. One of those is a soap based product and the other seems to be based on yucca extract. Both of those materials are surfactants. If you want to try that out without paying a huge premium for soap, I would try some generic baby shampoo from wherever. Put it full strength into your hose end sprayer (or mix it with beer like Jerry Baker ;0 ). Adjust the sprayer so that you see just see foam coming out. Spray monthly for 3 months and then skip to every other month. The idea of the surfactant is to break the surface tension of the water and allow it to penetrate deeper. The screwdriver does somewhat the same thing by opening up holes for the water to penetrate the first 3 inches without resistance.

Your light yellow grass with the seeds sounds like poa annua. You'll have puhlenty of that next year. I think preemergents were designed for poa annua.

Deep infrequent watering won't affect the grubs but it will positively affect the beneficial fungi. You want fungi. The soapy water should help, there, too. The best organic control for grubs in the south is beneficial nematodes. In the north milky spore seems to work better. Both have their idiosyncrasies. Beneficial nematodes need very wet soil to move around. Apply during a heavy rainstorm. Like now would be good in Tennessee. Milky spore needs to have a big presence in the soil. Seems that repeated apps every 6 months for 3 years is needed.

You called?

quick question for anyone. Beneficial Nematodes dont harm earthworms right?

There are 1,000s of nematodes, many rather innocuous, some predaceous, some parasitic, some actually pests. More than likely there are some nematodes out there that parasitize earthworms although I've not seen any reference to them, yet.

Here is a link that might be useful: About Nematodes

thanks kimmsr!

i have a question about the baby shampoo:
Will applying every three months or so affect the root depth growth.
when should it be scheduled around the application of soybean meal or alfalfa pellets?

Soaps, whether detergents, baby shampoos, Dr, Bronners Castile soaps, are surfactants, they reduce the surface tension of water so it penetrates a substance easier. Soaps do not, in reality, aerate your soil, they simply allow the water to penetrate easier.
If you need to aerate your soil you do not have enough organic matter in the soil and that is what you need to concentrate on, adding more organic matter.

the hard clay soil in my 3000 sqft front lawn is very low in organic matter, and i just got it to where it looks like a halfway vegetated plot lol. so i'm not really wanting to do any tilling or anything, though i have been using feed grains for soil food for bout 3 or 4 yrs now.
My hopes were to allow water to penetrate deeper hoping roots might drive deeper after it.