Cover crops

lbarnes lbarnes at
Mon Aug 16 22:56:03 EDT 1999

John- thanks for the cover crop info complementing Guy Clark's post! As
I understand it, the grass/grain component with nitrogen-fixers provides
extensive fiberous roots which absorb soluble nutrients (esp. nitrogen,
potassium) and serve as a "trap plant", keeping these soluble nutrients
from leaching below the normal root level, esp. with n-fixing crops in
winter (ex. rye/clover or vetch combos). All this living roots and
microbes probably buffer pH changes and make relatively  insoluble
nutrients (esp. P, Ca) gradually more available.  Several long term
organic growers have mentioned to me that clovers are best for longer
rotations (perennial clovers for at least a year) since it takes a long
time for them to develop lots of nodules compared to vetch or peas (I
have't studied this in detail- anybody with more info here?). Favas
sound like a great addition in fall/winter, since they are probably more
active at cooler soil temperatures during the winter. Note that cutting
legumes with root nodules will result in root tip dieback and a pulse of
soluble nitrogen from the drying nodules within a week or two from
cutting, dependent upon soil temps, microbe activity, etc. We need to
study mycorrhizal activity in these soils as well as N-fixing bacteria,
algae, etc. I believe that all "bare" ground should be immediately
seeded with seasonal  cover crops mixes (and green manures mixes; well
timed over-and-underseeding of cover crops to maximize soil activity
each year ; etc.) constantly growing roots  to provide habitats/nutrient
cycling/etc. for the complex soil biota which gives us all life! Happy
Trails, Lee Barnes (Southern Appalachian Mts.)

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