Every day on my commute to work I drive past a sod farm. Every spring I see them fertilize with liquid fertilizer, and water it.
Every summer I watch them peel off a layer of sod, leaving brown earth beneath it.
Yet I never see them replace the dirt!
While the sod farm is in a river valley, the river never floods further than a few feet beyond its bank, so I know the dirt is not getting replenished that way.
Can anyone fill me in on how sod farms keep from farming down to the clay/bedrock foundations?
Good question, doc! We have several sod farms near here, and I’ve always wondered the same thing. I don’t think they take a huge volume of dirt with each successive peeling up of the sod, yet some must disappear each time. It it replaced?
I have wondered the same thing and still don’t really understand it. However, the grasslings aren’t just converted parts of pure soil. They are made from atmospheric ingredients and stuff pulled from even deeper in the soil. Some loose soil goes with them for sure but I would imagine that fertilizing each year will extend the effective growing layers down bit by bit. As I said, I don’t really know but sod isn’t just converted dirt and the dirt layer is usually pretty thin leaving room for several years of growth before it goes down significantly.
One obvious question: Don’t sod growers eventually run out of topsoil after a few years of cutting layer after layer of grass? “If I had a dime or a buck for every time someone asked me that, I wouldn’t have to work,” Huggett said.
No, he explained patiently. It’s like this: The sod is cut into one-quarter to one-half inch thick sections. “And 99 percent of that is roots…It looks like a lot because all you see is the side view of the dirt.” Plus, because the crop is grass and there is no exposed soil most of the year, there is virtually no soil erosion from wind or water. The grass also collects dust blowing in the air and the grass’s extensive root system creates organic matter as it grows – as much as four tons per acre per year. “There is data that indicates that on a two-year cycle of harvesting grass, there is no more or less soil loss compared to regular row crops,” he said.
Live across the road from a sod farm. There is no additional dirt added. It is lower than surrounding farmland, but as Chief Pedant linked, most of the dirt stays every year.
It is true that sod farms do not remove nearly as much topsoil as one might expect.
However, the other reason they tend to not run out of dirt (at least in Southeast Michigan and Northeast Ohio) is that they are usually planted in recovered peat bogs. Those tend to be pretty deep, allowing many years of service before they are depleted. (And since sod farms tend to be on the edges of expanding suburbia, as one is depleted it is soon converted to a housing development, so it is rare to see an “abandoned” sod farm.)
There is a study going on in Rhode Island that claims that sod farms are actually removing 30 times the permissible amount of topsoil, but it is presented on the worst organized .pdf file I have ever ncountered. http://nesoil.com/ssssne/2007conference/Millar_SSSSNE2007.pdf