Back when he was in seventh grade, my son undertook a science fair project. For 60 days he monitored the germination and growth of four populations of bean plants: one control group, one with longer daily exposure to light, one with warmer soil, and one with both heat and light enhancements. His conclusion was that warming the soil significantly sped growth, but that lengthening the (simulated) sunlight did not.
Now there's evidence that grassland productivity, at least, is improved in some locations by warming climate not, as my son's experiment might have implied, during the growing season but over the winter. It turns out that an increase in thaw/freeze iterations (yup, the same folks who brought you pothole season!) can increase biomass production. (And remember, biomass is our friend.)
So, living in the currently frozen Northeast as I do, I'm wondering about the potential to add solar thermal enhancement to my kitchen garden. Possibly by just placing some glazing over the existing raised beds (something I can and should do right now), or possibly by installing south-facing solar collectors and underground piping (which would have to wait until early Spring, at least).
Sounds to me like I've got my own science fair project, if I ever stumble across any spare time.
Anybody tried anything like this?