Archives for posts with tag: Nitrogen fixing

It turns out that when I was describing the benefits of crop rotation two weeks ago (see May 4, 2014), I was only half right. The process can be much more complicated—and substantially more advantageous—than merely planting different families of plants in different plots each season. The key is choosing what to plant and the order in which to plant it.

A good example of a more scientific approach to crop rotation is described in an Op-Ed piece by Dan Barber, chef of the restaurants Blue Hill (in New York City) and Blue Hill at Stone Barns (in Pocantico Hills, New York), that appears in today’s New York Times (see “What Farm-to-Table Got Wrong”).

Chef Barber buys his wheat from a farmer in upstate New York. On a visit to the farm, he learned that the wheat is only planted at the end of a four-year cycle of carefully selected crops, each of which performs a specific task for conditioning the soil. The procession follows a basic order which can be modified as soil response and weather patterns dictate.

First up is a cover crop such as mustard, which cleanses the soil and adds nutrients. Next is a legume to fix Nitrogen. Rye follows which, apparently, crowds out weeds (and also “builds soil structure”, although no explanation is given as to what exactly this means). Last to be planted is the wheat, the crop that outsiders (and until recently, Chef Barber) would think of as the whole point of this enterprise.

What is lamentable in the wheat farmer’s case is that the market for what those outsiders might call the off-season crops—the mustard, peas and rye—is scarce. While the wheat commands high, New York City prices, the other vegetables and grains go unwanted and often end up as feed for animals raised as food. Such use is not considered by most experts to be a very efficient use of resources.

Chef’s response to this situation was to develop menu items at his restaurants that incorporate the lesser crops and thereby elevate their stature and, presumably, their price (I hope that he pays his farmer as much for the mustard, peas and rye as he does for the wheat). It’s an elegant solution—a no-brainer, in retrospect—and also a win-win. Really, it’s a win-win-win because not only do the farmer and the chef benefit but the patrons of Blue Hill get tasty meals out of it, too.

So, how might this concept apply to the backyard gardener? Well, I’m not sure about growing an entire planter full of rye or mustard but half of a planter mixed with other like vegetables or grains might work (especially if Chef shares his recipes). And I never feel like we have enough Sugar Snap peas so the year of legumes would not be a problem. The primary issue is space, something we never seem to have enough of.

Maybe the question for me is, where can I put two more planters?

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Having harvested the last of the string beans (see September 25, 2013), we decided it was time to clear out the vines and start readying the west planter for winter.  Some gardeners would chop up the vines and till them into the soil to decompose and add organic matter (so-called green manure or green fertilizer).  Others might cut the stems off at the ground surface and leave the roots in place, hoping that symbiotic bacteria (if present) would continue to fix Nitrogen in the soil.

But neither of these ideas appeals to me.  Even though the planter is not that big (four feet by 12 feet), turning the soil would be a lot of work.  And anyway, we are following the no-till approach, which moderates decomposition, improves drainage and minimizes weed growth by leaving the soil surface undisturbed.  Somewhat ironically, it also maintains better aeration by eliminating compaction and encouraging the earthworm population.  In fact, our soil is essentially turned over several times a year by an abundance of energetic Lumbricidae.

Leaving the roots in place would require less effort—even less than pulling them out.  However, we do not necessarily have Nitrogen-fixing bacteria and it is not clear that they would have enough time to make a significant contribution to the properties of our soil.  Besides, it is more likely that we have too much Nitrogen rather than not enough (see June 22, 2013), as evidenced by our crops of carrots, beets and radishes which produced more leaves than roots.

Being completely honest, it probably wouldn’t matter if either alternative had a scientific justification because pulling the vines out is more in keeping with my nature.  I have been described as a neatnik and it is a characterization I do not deny.  At a certain level, getting the planter tidied up for its long winter nap is much more important to me than ensuring that the soil has a proper concentration of Nitrogen.  Our soil’s nutrient distribution can be adjusted in other ways and at other times but I have to look at the empty planter all winter long.