What kind of grass do you have? If you have fescue you might have gotten a disease in there that took it out. Fescue will not return by itself and must be seeded almost every fall. Kentucky bluegrass, on the other hand, will refill assuming you have FULL sun.

You might consider getting your soil tested, too. If organic doesn't work, something is wrong and it is not the fertilizer.

I have mostly fescue. I removed a portion of my sod this past weekend to plant some bushes and I noticed white grubs.
Is milky spore the only organic method to get rid of those?
I had my soil tested last year. i don't have the report with me but I recall my nitrogen content was low and my soil Ph was below 5. They recommended a large amount of lime for the soil. But I thought I read where lime is bad for the microbes?

If you have mostly fescue, it will tend to thin out and get clumpy with an organic program. If you treat it with chemicals, then over time it will tend to get clumpy and thin out.

In other words, that's a feature of the grass, not the treatment approach. A fescue lawn needs to be overseeded periodically to stay thick.

Nitrogen will nearly always show up as low in a soil test. Many testing labs don't even bother testing for it. It's just something that needs to be replenished regularly.

I can't help with the grubs because I've never had them. And I have high pH, so I've never added lime, but I think people with low pH routinely add lime, even those who maintain their lawns with organics.

ive never heard of lime harming microbes, and if the DID and you are still inclined to add it, you could topdress with compost or spray with aerated compost tea to replenish those microbes.

But i've know plenty of people who add a little lime every year and it's never a problem.

my lawn sucks too, but it's because i'm not about to disc it all up to mix organic matter in there, though i should.

if you have earthworms, you are doing good organic practice.

my advice would be to keep doing what your doing and overseed like bpgreen mentioned. I would also try to find out if lime harms microbes and if you would like to do it anyway. Lime is not a......non-organic (?) practice.....it's naturally occurring. it's primarily pulverized limestone.

aren't there nematodes for grubs?

That's a yes on the nematodes, apply them later this summer. Lime is going to have to be applied every season to get it up around 6.5, soil pH can't be changed overnight. Lime is a mineral, so it's ok for organic use, however, if you have a good balanced treatment program, the pH will come up on it own as the soil build up. Don't go back to Fake Green, your lawn is still trying to recover from chemical dependency.

How much organic matter is in your soil?
How well does your soil drain?
How well does your soil retain moisture?
What is the tilth (workability) of your soil?
How much life is in your soil?
What does you soil smell like?
With a pH of 5 grass will have a real hard time growing. Whether lime would have an affect on the earthworm population would depend on which lime you applied. Ground limestone would have little affect while hydrated lime could cause great problems.

The lime can be important to allow the microbes to thrive. It is hard to really know but some may be negatively affected by the acidic soil (low pH). When you do lime, be sure to use the lime they suggested. There are two kinds. One has magnesium along with it. If they tested for magnesium and found it satisfactory or high, then they will recommend the other kind.

My limestone soil pH is 8.0 so having too much lime is not a problem.

Soil PH is absolutely critical to the success of growing whatever you want to grow... It just won't grow or recover from stress when the PH is way wrong... and PH of 5.0 isn't really optimal for most anything you can grow besides Centipede grass, Azaleas, Camellias, Rhododendrons, and Blueberries...

Almost all other turf grasses really like it better between PH 6 and 7.

Start there with the PH correction -- add your Lime. My guess is that you will be putting down several hundred $$ worth of Lime (Check your analysis results, you may need 2,000+ lbs worth for your lawn) Budget wise, you may need to spread it over a couple months... Buy $50.00 at a time and spread it evenly over the whole lawn... Do this each month until you get it all down.

You will see a big difference in your lawn -- even with a smaller 1st application of 300-400lbs of Lime... The grass will be able to absorb nutrients and it will thank you.

Then, don't give up on your Organic program to build the soil just because you didn't get it right immediately... It doesn't happen over night.... but it will get better over time.

Last, Overseed in late summer/early fall and it will help fill in your patchy lawn areas.

Thanks

John