I think you need to start with the soil test. The basic tests are usually PH, N, P, K and often micro-nutrients. Most state labs also give you a basic recommendation of what needs to be done. I imagine the lawn care company did a Fall fert, plus with your spring fert, you are probably ok on N and K. A lot of the Scott's (and other) ferts no longer routinely have P, which could be an issue on a sodded lawn, as root development needs P. Why one section is not growing is unclear, You don't mention how often you water. 1.5" a week (total, including rain) should be enough, maybe a little more if evap due to wind is drying the soil out. BTW, in my experience, the spreading ability of KBG is not as rapid as one might think from what one reads about it. Some overseeding is usually required to fill in bare spots, if any.

1. Most common reason is a nutrient or water defficiency, PH or soil structure. A comprehensive soil test from a reputable will determine nutrient problems and PH. A good soil test will give results forPH, TEC or CEC, P, K, calcium, magnesium, % organic matter, iron, and micro nutrients Take a look at logan labs in Ohio for examples. You can do a jar test (search "jar test" on this forum) to determine soil structure.
2. KBG really starts spreading in its third year. 99% of spreading occurs when soil temps are between 50-65 degrees--Fall and Spring. You can enhance spreading by mowing at 2 1/2" in the Fall and Spring and by fertilizing late August and late September with a high first number fertilizer (or better yet a tripple 10,12 or 19) then droping 46-0-0 urea as a winterizer after topgrowth has stopped (Usually in Nov.)
3. Keep spot spraying the weeds with appropriate Ortho products for specific weeds. Use a pre-m in both Spring and early Fall when you are not seeding. Scotts has a product that can be used when seeding but it only lasts 6 weeks.
In the meantime, mow high for summer, drop an organic fertilizer like Milorganite or alphalfa pellets and WATER.

With the $15 WI soil test you get essentially tests for 5 components of the soil. With the $20 Logan Labs test you get the following

pH
Organic Matter
Total Exchange Capacity
Sulfur
Phosphorous
Calcium
Magnesium
Potassium
Sodium
Boron
Iron
Manganese
Copper
Zinc
Aluminum
% Base Saturation Ca, Mg, K, Na

That same test looks like it would cost upwards of $60 at WI. Logan Labs has become the gold standard for soil testing for lawns.

From what you describe, the root of the problem is thin grass. It could be you are mowing too low, too. Tall grass needs less water than short grass and is much less stressed by the mowing. Mulch mow when you mow.

How much money are you willing to spend? I am going to show you a picture of a KBG lawn on which the owner has practically piled organic fertilizer. He applied both milorganite and soybean meal at a rate of 50 pounds per 1,000 square feet, every weekend, all summer long. He was trying to improve the organic matter content of his soil, but what he did was prove to the world that you cannot burn or hurt your grass by intentionally overdosing with ORGANIC fertilizer. Here is the picture of MorpheusPA's lawn in July 2010.

{{gwi:100977}}

If you ask Morph why his lawn looks that good, he will first tell you it is because he has used Logan Labs test results to adjust the micronutrients in his lawn. After that the attribution is to proper watering and the heavy doses of organic fertilizer. Why organic fertilizer? Because you can apply it in the summer to fix a lawn that is suffering from malnutrition when you cannot use chemicals. Chemicals in the summer will burn the lawn. My personal belief is that Morph wants to believe the soil tests gave him those good results, but I want to believe it was the fertilizer. We'll never know I'm sure, but I get those same results, without the soil test, year after year, when I apply organic fertilizer. My favorite organic fertilizer is alfalfa pellets (rabbit chow) because it works great and is less expensive than the others.

The normal application rate for a grain type organic fertilizer is 20 pounds per 1,000 square feet. Normally you would apply in late spring, early fall, and late fall. But if you are trying to fix something, you can apply it any day of the year. If you can find alfalfa pellets for $12.50 per 50-pound bag, the cost for this is $5.00 per 1,000 square feet. You would have to decide what your budget is for the lawn.

Here is a picture taken by mmrmumbles also in June of 2010. He had applied a handful of alfalfa pellets in May.

{{gwi:79339}}

Note the improved color, density, and growth. These are exactly the issues you are concerned about.

All that mmrmumbles results show is that alfafa pellts promote good growth. That doesn't mean other fertilizers won't do just as well.

BTW, while Logan Labs are good people, the Logan reports that I have seen don't provide recommendations on what the homeowner needs to do next. They are just the numerical values. Many state labs provide specific recommendations for fert and ph based on the test results. Logan is more of a professional site.

This post was edited by maynardGkeynes on Sun, Jun 30, 13 at 17:01

The intention of the mmrmumbles photo is to demonstrate that organic fertilizers work. Most people who have never seen them in action positively refuse to believe it works. Other organic fertilizers work as well with the possibly exception of feather meal types. I'm waiting for someone to do a demonstration like mmrmumbles did with feather meal.

Yes the Logan Labs do not provide recommendations. And yes, "many" (not all) state labs will provide recommendations. There is a growing little sub industry of volunteers who are willing to read a Logan Labs test and tell you what to do, how much of what to apply at a time, when, and where to get the chemicals. Search the Internet for andy, morpheuspa, and tiemco. They each have their specialties in reading the tests, but any of them are better than nothing.