Where do you live? How often do you water and for how long? What kind of sprinkler? How high/low do you mow and how often? Your pH of 7.5 and centipede are mutually exclusive phenomena. One or the other is wrong. Or you could have the world's sickest centipede. Centipede requires a pH in the 5s. St Aug, on the other hand, thrives at a pH of 7.5 and even higher. So there's something wrong with either the pH test or your grass ID. If you used a home done soil test, those are usually wrong. Get a real soil test for $25 at Logan Labs in Ohio. Skip the TAMU tests. If you ordered all the Logan Lab basic tests from TAMU, it would cost more than $60. Will need to post a picture of the dollar weed. Many (MANY) plants go by the common name of dollar weed. Some are more tenacious than others. The atrazine should have killed it in about 3 weeks time, but some plants come right back from seed. With atrazine you can only apply one time per year, so other methods must be used. If you take a picture close up (3 inches away), please take it in the shade or under a cloud to get the best contrast. I think posting a picture looking out across the lawn will give a very clear indication of the problem with your lawn. I suspect drought issues left over from last year and improper watering now.

Go to this web site and follow the flow chart. It is pretty good diagnostic tool. Good luck. http://www.ci.austin.tx.us/growgreen/downloads/lawnproblems.pdf

Carolinagirl, sit back, relax, take some very deep breaths. Embrace the calm. Relax. Sigh! It's only grass. Contrary to what the salesman told you, St Augustine is probably the easiest grass to care for. All you have to do is do it the right way. St Augustine only needs water when it needs it. You can get into a routine very easily which makes it less hassle for you. During the heat of summer I water once a week but I water for 3-5 hours each zone. For my sprinkler and water pressure, that means 3/8 to 5/8 inch of water (measured with a cat food can). That is only reserved for the hottest part of summer - once a week. This time of year I'm watering every other week on my way to once a month. Watering more often than that is ASKING for weeds to be a problem. Weed seeds need continual moisture on the surface to sprout. If you deny that water, they cannot sprout. Set your mower to the highest setting and have someone weld it in that position. THERE IS NEVER A REASON TO MOW ST AUGUSTINE LOWER THAN THE HIGHEST SETTING. Don't bag. I've seen St aug thriving at 30 inches high in the sand dunes in Texas. For a lawn it should be more like 4 inches when mowed. Tall grass can go much longer between watering because it has deeper roots. All that is a good thing. Fertilize with corn meal, alfalfa, soy bean meal, cottonseed meal, or whatever you can find cheap at your local feed store. Be sure it is ground up, though. If you fertilized with deer corn you would have a corn field to mow. The application rate is 10-20 pounds per 1,000 square feet. If you want more green for longer, bump it up to 40 to 60 pounds per 1,000. Use your wallet as a guide (fertilize until it hurts!). I fertilize on the federal holidays starting with Washington's Birthday. Then Memorial Day, 4th of July, Labor Day, and Thanksgiving. Call Trugreen and tell them you don't need them. You won't. Next year resist the urge to water weekly until the serious heat of summer. That alone will do more to prevent weeds than anything else you can do. You'll have to do something special about the button weed. St Augustine does not compete well against broadleaf weeds. Do you have so much you cannot pull it by hand? Nutgrass is a special issue. It is a swamp grass that cannot thrive in a dry soil. However, it can thrive in pockets of moisture. Let's say you dug a hole for some reason and put a better draining soil back in the hole. The soil around the hole can act like a bucket holding moisture for much longer than it should. That provides a little wetland area for the nutgrass to grow. Or you might just be in a low area or have poorly graded soil. In any case you are not on high ground in a desert! Any more info you have on that would be helpful.

I'm going to ask for another picture taken from 3 inches above a spot that shows both brown grass and green grass. Please take it in the shade like the area between you and the wagon in the second picture above. Generally with watering we talk about deep and infrequent. Deep means 1 inch all at one time. You can time how long it takes your sprinklers to deliver 1 inch by placing some cat food or tuna cans around the yard. Put them in the green spots and the brown spots. The time it takes to fill them is your watering time. My oscillator sprinklers, with my hoses and water pressure, take 8 hours to fill the cans. High flow in-ground systems can fill the cans in 20 minutes. Your time will be different. Infrequent, the other part of the watering mantra, means you wait until the soil dries out from the previous watering. There are many factors in determining when to water but they all simplify down to air temperature. Now that the temps are in the 80s, you can water once every 2 weeks. With temps in the 90s water once a week. With temps in the 70s, water once every 3 weeks. When it's cooler, water once a month. This is the single most important key to success with St Augustine. Mowing height is the second important factor. Always mow at your mower's highest setting. Hopefully that is 4 inches rather than 2.5. My neighbor's riding mower only goes up to about 2.5, so I quit using it. I'll mow weeds at that height but I steer around my actual grass (I've moved to a weedy lawn in Bandera). Tall St Augustine grows much deeper and more drought tolerant roots. These two factors account for at least 90% of success with St Aug. Fertilizer is much less important. It counts, but if you're trying to improve your current lawn, watering and mowing are the most important. Nice to see you're using organics. I can save you some money on that if you like. Rather than paying $20 for 40 pounds I buy the raw materials at the feed store for more like $10 for 50 pounds. The ingredients in the Gardenville product are unequaled; however, not always needed. If you used that once every year or two, along with 3 total applications per year, you'd be fine. I fertilize with either corn meal ($8) or alfalfa pellets (rabbit chow, not horse cubes ($12)). The application rate is 15-20 pounds per 1,000 square feet or about the same as the Gardenville fert. You can use these organic products any day of the year, or every day of the year, without any fear of hurting anything. They don't need to be washed in like chemical fertilizers. There is no reason I can think of that the grass over the septic fields would not be growing. The grass over top of the concrete tank might need more water, but the rest should be fine. I would suspect lack of water (or too much water). If you get your water and mowing height adjusted, you should see it turning around. Please post another close up picture so I can look for signs of disease. Rather than writing an essay on disease when you don't need one, I'll wait for the pic.