Tuesday, August 7, 2012

A Paean to Warm-Season Grasses

A follow-up to my previous post, on the drought. I took a trip down to Nichols Arboretum, a beautiful property run by the University of Michigan. They have a restored tallgrass prairie fragment there, called "Dow Field". For you botany nerds, it was first described by Henry Gleason as he passed by on the train on his way out of town (Ann Arbor).

Dow Field, like most tallgrass prairie, is dominated by C4 grasses, especially Big Bluestem (Andropogon gerardii).  I wanted to see whether my idea of having C4 (warm-season) grasses as part of a pasture base could be supported by a visual inspection here (i.e. am I just full of shit?).

What I saw was encouraging, although not quite as lush as it should be this time of year. When I read the site description for Dow Field a couple years ago, I recall it mentioning the soils were droughty- so there's  reason to believe that the grass would be even healthier in a better soil. But nevertheless, check it out:

Big Bluestem (Andropogon gerardii). Fairly typical of the exposed portions of Dow field.

I found a seemingly inexplicable clearing in a side portion of the field. There was a layer of dead grass, with younger growth of Big Bluestem, and lots of thistle. I suspect that the Natural Areas Preservation Program may have treated the area with herbicides earlier in the season to fight "invasive" (C3) grass.

A pretty prairie flower. Don't know what it is yet! 

The next photo shows my dog, Chloe, standing next to some fresh Bluestem growth. It was looking reasonably healthy, and would be at a good time to graze- still lush and vegetative. This gives me confidence in the warm-season grasses as providing valuable diversity and resilience for pasturage and hay. Imagine what this field would look like in a better soil, with more shade, and possibly flood irrigation...

Not far from the cleared patch, I shot this photo to show the awesome height of mature Big Bluestem. This was the tall-grass prairie that impressed the early settlers of the Middle West. It was a beautiful, diverse ecosystem, intergrading on the eastern front with oak savanna, and oak-hickory and mixed deciduous woodlands. These ecosystems sustained many herds of Bison, and numerous tribes of native Americans, adapted to the periodic vagaries of an intense continental climate. Indians burned the prairies annually to facilitate hunting drives, particularly in the fall (October-November). The immense heat and smoke from these fires so intimidated the early white settlers that they coined a term "Indian summer" to refer to the fire season

Chloe and the Big Bluestem 

I know the agriculturally-minded will scoff at my faith in the utility of the warm-season grasses for hay and pasture. It is true that, normally, their growing season is shorter, and the growth coarser and lower in protein than most of the introduced cool-season grasses (e.g. bluegrass, orchardgrass, etc.) Switchgrass is already well-accepted for this role south of Ohio. I'm not suggesting that, this far north, they should be the main basis of a pasture program. But I think that handled correctly, they could contribute mightily to resilience in the face of increasing climate vagaries. For comparison's sake, check out some local, similarly unirrigated cool-season grass:

Where's the nutritive value here? 


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