[Market-farming] Hairy vetch & Corn

Steve Diver steved at ipa.net
Fri Feb 15 09:21:51 EST 2008


>Can Hairy vetch be planted along with corn to supply the corn with nitrogen?
>
>Andy King
>Sunflower King's Farm
>http://www.sunflowerkingsfarm.com/
>PA Zone 6


Normally it doesn't work that way; i.e., interplanting legume "with"
the cereal crop to get transfer of biologically- fixed N between
roots.  Hairy vetch and related cool-season leguminous cover crops 
are typically sown in the fall as winter annuals.  When they are 
ploughed down the following spring the nitrogen is release during 
decomposition.  

The good thing is that the mineralization / N-release rate and crop 
takeup / fertility-needs are fairly well matched.  So it a sustainable 
practice and it supplies N in organic farming. 

In pastures -- which are a mix of perennial and annual grasses, legumes,
and broadleaves -- you can get transfer of Rhizobium-legume nitrogen
to grass roots via mycorrhizal fungi "during" the growing season; i.e.,
active transfer between living organisms.  We facilitate this kind of 
ecosystem functioning in Texas using soil biology management practices.

In typical legume/grain crop rotations there is a lot of tillage and 
use of ag chemicals. These practices drastically reduce mycorrhizal
colonization and related pieces and functions of the soil foodweb. 

There are practical ways to increase mycorrhizal colonization and
soil foodweb functioning that can result in active N transfer. 
You can verify what the situation is using lab-based soil tests 
and on-farm microscopes and soil health test kits.  It's do-able. 
I can think of a few well established organic farms that use 
ecosystem approaches where you may find this happening.   

At the same time, it's not that you are getting active
N transfer from mycorhhizal-rhizobial interactions alone, 
as if that is the linear effect that produces the corn crop.  

It is the cummulative ecological effect of managing cover crops, 
proper tillage, mulched surfaces, active biology, organo-mineral 
complexation, soil aggregation, and related soil-building practices 
that result in a robust soil foodweb that functions on all levels. 

Foliar application of N-fixing bacteria such as azotobacter 
can also result in N supply to the growing corn crop.

Steve Diver
Texas, Zone 8 








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