Re: Nitrate leaching in No-Till

Ray (and others),

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 
several counties.

ray,  thanks for the comments.  

and to all a good day

noah ranells
soil and water conservation