Here's the problem in a nutshell with having a nice bermuda lawn (at least in my opinion): Bermuda takes the same kind of care that weeds take. Bermuda likes to be mowed short. If you mow it short enough (lower than 3/4 inch and preferably lower than 1/2 inch) and give it enough fertilizer and water, it will look pretty good - very dense. But being low if there are any holes that allow the sunlight in, the crabgrass seed is going to germinate. And, as you are seeing, crabgrass will easily crowd out bermuda. (so anyone who thinks there is no cure for bermuda, just look at a bermuda/crabgrass mix and you'll see for yourself.)
I visited my mother in Temecula, Calif last month and took pictures of her neighborhood lawns. One was 100% crabgrass and didn't look too bad. Well cared for crabgrass can be okay if a little yellow. But that entire lawn will die out completely in the early fall, winter and most of spring. I also saw 100% clover lawns. They didn't look bad either. I almost got a great picture of a clover lawn but the guy mowed it in the time it took me to get my camera (dang).
Crabgrass will die out completely in the fall. Bermuda will only go dormant in the fall. That means the bermuda will come back next spring. The crabgrass will only come back IF it gets "proper" water and sunlight. That means it needs water for several days and seed exposure to the sun. If you can control your watering (and Mother Nature) so that you only water once a week, the weeds should not come up. If you grow grass that likes to be mowed high (like St Augustine, fescues, blue grasses), then you should not have any problems with bermuda or crabgrass. Having said that, fescues can be a weed problem if you don't seed them heavily enough. They don't spread like the others do.
Bermuda likes LOTS of fertilizer. You can fertilize with real fertilizer (not molasses) every other month (for soy bean based fertilizers) or every month (for corn meal based fertilizers). Molasses provides no protein to the microbes. The ground grains provide enough if you use enough of it often enough. For many people this need for so much fertilizer is a problem with bermuda. And if you want it to look nice, it needs to be watered just as much as other grasses.
You could start a St Augustine lawn today if you want to. Go get as many flats of St Augustine as you can afford (and have time to plant). If I was going to start with a few flats like this, I would dig out the bermuda/crabgrass with a claw and fit the flat in. Push the flat down to ensure good ground contact and start watering it. Starting with just one flat you should easily have 100 square feet of St Augustine in a season. If you place the flats strategically around your yard, they will grow together taking the bermuda out along the way. You might still have some bermuda next spring, but it should be mostly gone by this time next year. St Augustine needs water. If you let it dry all the way out, it will not go dormant, it will die and the bermuda will fill back in. But keep after it with water and the St Augustine will predominate.
You can cure hard soil. First of all think of soil as being like a sponge. A sponge is very hard when dry and very soft when wet. Also water will roll right off of a dry sponge but not a wet one. Your soil has to accept the water. The reason some dry soils accept water faster is the fungal quality and content. You need to grow a great herd of fungi. You can do that with a soaker hose and organic fertilizer. Run the soaker hose back and forth across the high point of your yard. Connect it to a faucet that is just trickling. This means the water is trickling out of the faucet. It should take about an hour or more to fill a gallon jug. Then leave the faucet trickling like that for 3 full weeks. Your soil should eventually become VERY soft, like a sponge. Then move the soaker hose only 18 inches down the hill toward the lower parts of your yard. Repeat the process until you get to the bottom of your yard. Then repeat from the top. If you do that for two full cycles, maybe three, your yard should have all the right fungi. Then let the lawn dry out until the grass looks like it needs water. You will find that the surface of the soil turns VERY hard again but the grass continues to grow nicely. Don't water when the soil gets hard, water when the grass needs it. Then when you water the water should soak into the soil easily and soften the ground. Keep watering until the soil softens enough to feel spongy again. Then let it dry out again like before.
Does that help?
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