Low maintenance lets bermuda out - nless you don't care when it gets weedy again. Bermuda should be mowed 2x to 3x per week in the summer and fertilized heavily every month.

Are you sure the centipede is not St Augustine? The easiest way to tell is if the tips of the blade are blunt or pointed. Blunt tips is St Aug. Pointed is centipede.

St Augustine will choke out most other grasses with few exceptions. Alfalfa is not a grass and should be sprayed to get rid of.

Are you in a neighborhood where people will complain if the grass is too tall? I ask because if you leave St Augustine alone without mowing, once it gets up to a foot tall it can survive for several weeks without water. But if you mow it then it must have deep water every week.

Pictures are always good.

I'm in country no neighbors . What should I spray to kill the Alfa hay

As you can see there's clearly a big dead spot

This is close up of dead area

You might consider an alternative to conventional turf grasses and try a mix of some relatively tame prairie grasses. In Texas we have a blend of buffalo grass, curly mesquite, and blue grama called Habiturf. Another alternative is a mix of wheatgrasses which grow well in your area along with blue grama and possibly others I'm not aware of. These are slow growing grasses which happen to make an excellent lawn. The drawback is that when they do produce a seed head, it might shoot up 14 inches. Lawn owners won't tolerate that so they are left out of the mix for typical homeowners. But the good news is the well behaved grasses don't send those seed heads up very often. You might get away with mowing only 4 times per year and never fertilizing.

Here is a picture of a mostly wheatgrass lawn mixed with blue grama and strawberry clover. The lawn is in the Salt Lake City area and is owned by bpgreen.

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You would have to find the varieties of wheatgrasses which grow in your area. Google is your friend.

When it comes time to renovate, since you have enough land to justify it, get someone with a box blade to scrape off the surface. Before you do that, you might want to kill the bermuda and other weeds which will return. That is a 3 week process, so plan ahead.

Plowing will not kill the alfalfa. That will require a program of 2-4,d (as found in Weed-B-Gone Clover, Chickweed, and Oxalis), Banvel (farm and ranch store), and roundup. Much of the alfalfa today is immune to Round Up, so you can't just hope that will work. It is not immune to 2-4,d though.

So would you recommend to spray those chemicals then scrape the surface with box blade then plant some sort of mix like your talking about . Would it plant on flat surface or would I need to rough it up some . When would be the best time to kill then when to plant

Check with the vendor for your seed to find out when it will sprout best. Unfortunately sometimes that is in the spring due to many factors. For example, crabgrass only sprouts in the spring or early summer. When the days start to get shorter it won't sprout. I'm not suggesting you plant crabgrass, but it does suggest that if you pick seeds that sprout best in the spring, then you will also get plenty of crabgrass. But you can deal with that later. Find out when the best time to plant is, and then back off 3-4 weeks from there to find the start date for spraying.

If you run a box blade over it, you can plant right into that finished product. Be sure to roll the seed down with a water filled roller or other implement pulled behind a tractor. You have too much area to push a roller around.