i agree with your concept of using cropping systems to efficiently utilize N and
attempt to avoid the leaching of water soluble N.
rw-We have observed higher nitrate in groundwater under hairy vetch than
under fertilizer N plots in some instances, because of poorer control over the
timing of N release from the vetch.
nnr-we have also observed this under hairy vetch and austrian winter pea. But
if we had a mix of the legume and cereal rye the soil N pool is 50% less
compared to the monoculture legume.
rw-This situation may occur a week or so after killing a no-till vetch
nnr-under our climatic conditions, i think some leaching may also occur during
the March and April prior to killing the cover crop. During good early spring
growing conditions (warm and somewhat wet), we see a thin decomposed layer of
cover crop just above the soil surface and it seems to be oozing nutrients.
Even if we do get the corn or other summer crop planted in a timely way, some of
that N may be lost during late spring soaking rains which occur prior to
elevated corn N demand. It is important to recognize that the amount of N lost
in this situation may be quite small.
rw-Controlling cover rate of N release by using mixtures of legumes and grasses
with various c/n ratios and decomposition rates is another possible
strategy. Noah, I know you've researched this. What have you found?
nnr-I mentioned earlier that a grass-legume mix (biculture) does a good job at
reducing soil inorganic N levels at corn planting. This especially true of
cereal rye, which does a much better job at scavenging soil N compared to a
fall-planted spring oat and wheat. A report is in press with Agronomy Journal.
I was just talking with a farmer who tried no-till a few years ago and bagged
it. Now with the advent of commercial strip tillage equipment he is willing to
try again. This is just an example of one of the more exciting parts of no-till
aka conservation tillage - the development of appropriate equipment. And
believe it or not, north carolina farmers are making no-till tobacco work in
ray, thanks for the comments.
and to all a good day
soil and water conservation