Question
Hi Charlotte,
 I manage 2 lawns in the St.Louis area. They were sodded last year, and have a very dense clay base of soil below the sod.  The majority of the lawns are in direct sunlight.  They also both have irrigation systems.  My question is in regards to crab grass. I have used a preventative and with seemingly no results. I used scott's brand, and followed the directions. As soon as the lawn started growing, crab grass was everywhere.  Can you give me any methods for eliminating this pest once and for all.  Thank you for your help.
  John  

Answer
Hi John;
First, with that clay soil, you are never going to have a good lawn, untill you loosen it up.
Water will not drain properly, and the grass roots will stand in water all the time.
Weeds love popr soil. They will not thrive in rich soil.
Fertilizers kill beneficial microbes that enrich the soil. Sugar or dry molasses, keeps them alive. Those microbes work 24/7 enriching the yard, the year round. With good rich soil, you don't need fertilizer. I haven't fertilized in about 7 years (since i started using sugar).
I use 1 pound sugar per 300sq.ft. in sprinf and fall, water it in, and that's all.
You put down the sugar and water it in, and in a couple of weeks or so, you start noticing fewer weeds. The next spring some will come up, but not nearly as many. About the third or fourth year, you will notice that none come up at all. the only thing I can see that would slow this down, might be the clay soil not draining well enough.
I had crabgrass, johnson grass, dandelions and a host of other weeds. I haven't seen one sprout up in 5 or 6 years, and I have not fertilized either, just put down sugar in the spring and fall and watered it in.