When farmers in Maryland mention their turf, they're talking big business.

Maryland's most important "crop" is grass -- the kind that covers golf courses and lawns. It takes up more acreage than any crop except corn. It's grown by more landowners and generates more expenditures than any other green leafy substance in the state. In fact, if not for grass, many Marylanders would be high and dry.

That's the message of a new $20,000 report, produced by the Maryland Department of Agriculture and funded by the Maryland Turfgrass Council Inc. The survey puts turf's total contribution to the state's economy in 1979 at more than $518 million. That's no small potatoes, say Maryland turf growers.

Predicatably, homeowners have the lion's share of the state's maintained grass -- 60 percent -- and their attempts to keep it green cost more than $95 million annually. Strips of green lining the state's highways are a distant second with about 8.5 percent of the grassy area, and cemeteries are next with 7.9 percent. Other strong finishers include golf courses and the rolling lawns of institutions of higher learning.

John W. Strickland, president of the Turfgrass Council, said last week that the turf farmers who make up his organization hoped by funding the report they could prod the state legislature into giving more money to grass-roots research.