   Traditional row crop production is not a natural system,
notes Chris Lawrence, NRCS agronomist in Richmond, Va., The way
to grow crops in a more natural system is to imitate nature, the
Virginia agronomist says.  The first step he says is to make a
commitment to long-term, no-till farming and to building
nitrogen in the soil. A key to that commitment it always have
something growing in the field. In a naturally occurring system,
there is always something growing to keep nitrogen production in
balance. Over time, he says, keeping something growing in the
field all the time will have environmental, agronomic and
economic benefits.  It is critical in this long-term investment
to have a legume in the rotation. Lawrence points out the
obvious, that N has to come from somewhere and legumes are
nitrogen-fixing plants.  “Asking grain farmers to make this kind
of commitment is difficult,” the Virginia agronomist admits. “It
does add an extra cost, and it doesn't provide much return on
investment for the first few y