Subject: Re: what plants "fix" nitrogen?

From: Tristan Hatton-Ellis <[email-masked]>
Date: Tue, 5 Mar 1996 12:51:00 GMT

Travis Saling <[email-masked]> wrote:

>> To be more correct, it's not the plants that fix the nitrogen, but the 
>> bacteria that colonize the "nodules" on the roots. If you want to be sure 
>> that you are getting good colonization, you should add the bacteria as 
>> well as planting the legumes. Inoculants are available (SNIP)

>Okay, okay.  I think it's worth a test sowing, though, to see if you need 
>to inoculate; at least for the common legumes.  I've never inoculated my 
>seeds or soil, and the favas (vicia faba), dry and snap beans (phaseolus 
>vulgaris), and peas (pisum sativum) all develop lots of those root nodules 
>which indicate colonization.

>Travis
>Sumner, Washington
>USDA zone 8, Sunset zone 4

There is a research group here at Bristol working on genetic diversity of 
Rhizobium leguminosarum, probably the best-known N-fixing bacterium; they 
culture them from soil isolates, and then DNA fingerprint them. Basically, 
even in arable fields there seems to be a healthy diversity of different 
strains of this bacterium in the soil, and so I would have thought that in 
most cases inoculation of soil is a complete waste of time. Gardeners have 
grown legumes for a long time now without adding soil inoculum every time, 
and I see no reason why they should start now. I agree with Travis - have a 
look at the roots of your peas, and you will almost certainly find lots of 
nodules. Even if there aren't any, this isn't necessarily a problem (some 
legumes don't nodulate)unless the plant isn't growing well.

If it aint broken, don't fix it!

Tristan