Well if you do a little internet searching you will see that university turfgrass programs all say mulch mowing doesn't contribute to thatch. Just because you got thatch and you are mulch mowing isn't causal, it's correlative.(Thatch only occurs on well maintained turf by the way, so the act of you getting the lawn in shape probably contributed to higher thatch production) Certain grasses are thatch producers, KBG, and Fine Fescues are thatch producers, while tall fescue and perennial rye generally don't. If your soil has a high OM content, is balanced, and has good microbial activity, thatch shouldn't be much of a problem. Also I have read that spraying your lawn with molasses in a hose end sprayer can help reduce thatch, but I have no experience with it.

Your watering plan for the boulevard strip is fine, but you want to shoot for one inch of water 1X per week, whatever time that works out to be. The three times a week for 20 minutes is not recommended. Deep and infrequent is the general rule of thumb. Of course some soils and climates dictate a different watering schedule. What is your soil like? Ever have soil tests?

In order to get rid of thatch, stop watering the lawn 3x per week for 20 minutes at a time. When you water frequently and shallow like that, your grass does not need to develop deep roots. With frequent watering and foliar fertilizing, I've seen an entire lawn develop roots on top of the soil surface.

You already have a build up you don't like (call it thatch if you like). You can leave that alone and eventually the organic matter will decompose it. Molasses might help. Note my lack of enthusiasm for molasses. I use it occasionally for other things. I'm sure it helps to feed bacteria, but I wouldn't go overboard about it.

What is OM? Our soil in eastern Colorado is very clayey. And if you can believe, getting soil tested out here, if done professionally, is only done for big farms and commercial projects. I've not found anyone who will do soil testing for residential lawns.

Our front lawn is probably KBG (in Colorado? REALLY?), but when we had landscaping done in the back yard, I insisted on drought-resistant grass; it's a mixture of three different grasses, at least one of which is fescue, so that should help.

Any other ways I could help increase microbial activity or thatch breakdown? I've heard about molasses as well, but am willing to consider other options. What about adding earthworms to the lawn?

OM=organic matter

Your soil might act like clay. Look up jar test in this forum and run that to see if you really have clay. Magnesium in the soil can make loamy soils act like clay.

The lawn nuts around the country are getting their soils tested at Logan Labs in Ohio. For $20 you get a test that would cost triple that at any other lab. Get the test and post your results here for explanation of what to do.

In Colorado you might have really good luck with a mix of the wheatgrasses along with blue grama. Those are all prairie grasses. When planted together and mowed, they look like this...

{{gwi:83633}}

That lawn belongs to GW member, bpgreen in SLC, UT. He also has strawberry clover in it which you see towards the front of the image.

If you want to consider the modern approach to organic lawn care, go to the Organic Gardening Forum and find the FAQs. At the bottom of the list is the Organic Lawn Care FAQ. Read that and come back with questions.

In my opinion (held by many others) KGB produces the most apealing lawn there is. KGB is very high maintenace grass. KGB produces thatch. Thatch hinders water and nutrients from reaching the soil. Can grass clipping become thatch? Sure. Any plant material that does not decompose can become thatch. Grass clippings/blades contain many nutrients (a lot of nitro for one and upon decomposition return those nutrients to the lawn))and are the most tender part of the grass and readily decomposed. Beneficial microbes decompose thatch. And therein lies the rub--how to increase microbial activity. I use humates, but tiemco and dchall can probably give other suggestions. It has been my experience that a well maintained KGB lawn produces thatch faster than it can be naturally decomposed. I'm wondering why you feel thatch was a problem. What signs were there that thatch had begun being detrimental? Did you have over 1/2 inch of thatch?

I second what tiemco says in regard to watering.

BTW a soil test can be useful for any user- not just the big boys-take dchall's advice on Logan Labs.