Question
I live in S. Florida and my yard has St. Augustine grass.  My poor lawn several strikes against it.  Drainage is poor to VERY poor since the yard and house foundation is made from crushed coral with a 1 to 1 1/2 inch topsoil layer.  The coral base does not drain well (i.e., 2-3 day puddles in some areas after heavy rain).  My problems include: many brown and yellow-brown areas in my lawn which seem to have gotten worse (see http://www.geocities.com/sascampold/lawn.htm for samples), the ground is spongy when I walk on it, the grass seems to lay flat, and in some area where soil is exposed and grass not growing there are some plies of dirt on top.  Last issue is I live in an environmentally sensitive area with lots of wildlife.

Is it possible that I have grubs (dirt piles), fugus, and root rot (poor drainage), and possilbly more?  If I do have one or more, is there a specific order in which I should address these problems (drainage first, then grubs, etc.)?  Finally, are there organic means to address fungus/grubs since my backyard is on a lake and drains directly into it.  This lake frequented by numerous birds, some of which are endangered?  Sorry for the novel and thanks for you attention to this matter.

Answer
You need to deal with drainage first.
St. Augustine also benefit from being dethatched annually. this involves ripping out dead rhizomes which can create a barrier through which oxygen, water and nutrients have difficulty penetrating.
Fertilize your lawn monthly through the hot summer months. You can buy organic fertilizers at garden centers.

You may have problems with grubs, fungus etc. Solving drainage will likely take care of fungus. Grubs can be solved with beneficial nematodes (see gardensalive.com). However, do not be in a hurry to add these. drainage is probably (most likely) your biggest problem right now.

You may have to have a landscaper come in a drill down through the coral.

Link:
http://gardensalive.com/item_display.asp?ProductNumber=5000