I just defoliated and weighed a piece of my bamboo patch. I got 33 lbs of fresh weight leaves and twigs (I took the parts I observed my cattle eating) off 100 sq ft. I'm not sure what % moisture it was, but if it is similar to the sample buried in the snow I sent last winter (44% DM) that makes for just over 3 tons/acre of forage DM in the leaves and twigs. I sent a sample to DairyOne for analysis today since the numbers swing by many pounds for every % difference. If there is merit I want as much data as possible.
My neighbor who fertilizes and cuts hay gets 2.5 tons of high quality hay off the same soil. And he's up to his eyeballs in debt for the machinery required to take that hay.
I checked on the leaf growth more regularly this year than in past years. I think my casual observation about the mass of leaves coming in a flush in the spring was not accurate. Yes the visual space is taken up quickly in June when the new canes push leaves, but the growth habit of this particular bamboo is such that each twig (not too sure about bamboo terminology) pushes a single fresh leaf continuously thorughout the summer and fall. As soon as the twig finishes a new leaf it starts on another. The only twigs I see not pushing more and more are those that emerge low on a shoot and get shaded out by the canopy as it closes above. So I think the mass of leaves in a given patch will continue to increase at a near linear rate from June until growth cease sometime in October. And actually the rate of mass building is slightly better than linear because new canes emerged throughout the summer and fall this year. I don't know if it liked the conditions this year more or (I suspect) the patch is just big enough now, and has sufficient energy socked away in it's root system, it spent more on new canes throughout the growing season. I just counted ten new canes emerging around the edge of the patch (no twigs or leaves yet, still pushing upward). In previous years I saw a few new canes come up in August, but that was the latest. I saw a few in Sept this year and though "wow", and now I see a bunch in Oct.
I also have an off-the-wall hypothesis to test this winter. I think it's possible that the winter kill on the canes comes from dessication in the cold winter wind. I'm going to have my ruminants defoliate the whole patch before we go deep below zero this winter and see if the canes can survive and push new leaves in the spring. If they can do that there would be an additional boost in total yield/year.