From a Florida State site:

"Nutsedge Control - The predominant nutsedge (often inappropriately called nutgrass) weed species in turfgrasses are yellow and purple nutsedge. Other, more local members of the Cyperus genus include annual or water sedge, perennial and annual kyllinga, globe sedge, Texas sedge, flathead sedge, and cylindrical sedge. Path or slender rush, a member of the rush (Juncus) family, also can occur in some turf situations.

These weeds generally thrive in soils that remain wet for extended periods of time due to poor drainage or excessive irrigation. The first step in nutsedge control is therefore to correct the problem of continuously wet sites. Do not overirrigate an area and, if necessary, provide surface and subsurface drainage.

Historically, chemical control of most sedges was with repeat applications of the organic arsenicals (e.g., MSMA). Although effective, the treatments are slow to kill the weeds and repeat applications are generally necessary, resulting in extensive damage to certain turf species.

Selective yellow nutsedge control is possible with bentazon, an herbicide found in products such as Basagran T/O® and Hi-Yield Basagran®. Bentazon is a contact material, meaning it will control only those portions of the weeds treated. Complete coverage of weeds is therefore necessary for greatest bentazon activity. Even with good herbicide coverage, regrowth will normally occur from the roots and tubers, and repeat applications will be necessary.

Purple nutsedge can be controlled with herbicides containing either halosulfuron or imazaquin, sold as Manage® and Image®, respectively. As with bentazon, repeat applications - possibly over several years - will be required to control all the underground reproductive parts or purple nutsedge."

Here is a link that might be useful: Nutgrass (nut sedge) control

Ccodd, first of all, what type of sod is it? Marathon? Marathon II or III? St. Augustine? etc.

Most nutsedge in California is the yellow. I am assuming you had the nutsedge before you installed the sod and of course that is when it could have been killed easier. What ever you do it will take time and if you had your sod installed professionally I would see if they would be willing to take on the problem. Al

I agree, don't over water. Next, I found that just growing really good grass and mowing more often, like twice a week instead of once, slowly let the grass win. You can use an asparagus fork and jab into the soil to carve up the root nuts, but that's a lot of work and may also just divide the nuts into more nuts unless you are very through. Mainly just grow such good grass the sedge looses.

St. Augustine beats the nutgrass & bermuda grass creeping in my front lawn.

Marathon 2 (fescue) in my backyard does not. I blends in with it but it tends to grow alot faster than the fescue. Since I mow every week it doesnt get that bad. I also fertilize and spread fescue seed every 2 or 3 months to keep it thick. I have also cut back on watering as this was also part of the problem. Was watering twice a day for 15 mins each time. Cut it to just the morning now.