Converting grass stolon planting rates from bushels to mass per area

Planting rates for grass stolons are usually described as bushels per acre in the USA, I think. In Thailand, the rates are often described as mass of stolons, i.e. kg/m2.

I was at a seminar in Thailand a couple months ago, and a speaker mentioned a planting rate of 800 bushels per hectare. One of the audience members asked me what that rate was in kg/m2. Here’s the e-mail I sent with the best answer I could come up with:

I checked about the planting rate of 800 bushels per hectare. I can’t convert exactly to mass/area, but I can explain what the definition is.

1 bushel is about 35 liters of volume [I got this by using Google’s conversion service for volume, which says 1 U.S. bushel is 35.2 L. The Richardson and Boyd paper mentioned below gives the conversion as 1 bushel being 0.055 m3 (55 liters) of volume.]

By definition one should get one bushel of sprigs by shredding one square yard of sod (0.84 m2 of sod). [I get this definition from Richardson and Boyd (2001) who cite a 1999 publication that I have not read by McCarty et al. as the original source. I note here that I also calculate 1 square yard as being 0.84 m2, and the Richardson and Boyd paper give the conversion as 1 square yard being 0.914 m2].

The technical definition of how much sprigs this should be is therefore to take 672 m2 of sod, shred it, and that should make 800 bushels. Then, spread that 672 m2 of shredded sod onto 10,000 m2.

I think the planting of warm season grasses in the USA involves more shredded sod, and in Thailand it seems like a lot of verticutting, but not so much shredded sod. So you can also check the conversion by looking at the mass of about 35 liters of sprigs.

That’s the best conversion I can make.

This conversion is something that Mike Richardson and I have discussed a few times. We recently did again, concerning the planting rate of manilagrass (Zoysia matrella ‘nuan noi’) nurseries near Bangkok. These fields are planted by taking 1 m2 of sod and planting it to 4 m2. What’s that planting rate in bushels?

To answer his question, I’m going to estimate that the manilagrass sod cut from the nurseries in Bangkok is 1/3 the thickness of sod cut from nurseries in the USA. I can easily pick up a large piece of sod – this is a piece of seashore paspalum – cut from the nurseries near Bangkok because it is mostly a mat of stolons and contains very little soil.

I’ll further estimate that the quantity of stolons and rhizomes (or perhaps the number of nodes) in 1 m2 of sod in Bangkok is half the amount of 1 m2 of sod in the USA. If that’s approximately correct, then I’ll extend that estimation to predict that 1 m2 of the thin 5 or 6 week old sod in Bangkok would produce half the bushels of an equivalently sized (in area) piece of sod in the USA. I expect that 1 m2 of sod in the USA will produce by definition 1.2 bushels. So I’ll estimate that 1 m2 in Bangkok will produce 0.6 bushels.

With that rough approximation, the planting rate of 1 m2 to 4 m2 at the nurseries in Bangkok would be about 0.6 bushels to 4 m2, or about 600 bushels per acre.

If we say the thin 5 or 6 week old sod in Bangkok produces the same quantity of planting material as the sod in the USA, then the planting rate to reestablish the nurseries in Bangkok would be about 1200 bushels per acre.