Subject: Re: what plants "fix" nitrogen?

From: Travis Saling <[email-masked]>
Date: Tue, 27 Feb 1996 22:36:54 -0800

> >What plants can i grow in my garden that will "fix" nitrogen?  I would
> >be interested in both food crops and flowers.  The only one I can
> >remember is peanuts, and I may well be wrong.
> >
> Hi Bryan - All legumes fix nitrogen - sweet peas, garden peas, snow
> peas, sugar snap peas, crowder peas, string beans, shell beans, dry
> beans, fava beans, scarlet runner beans, cleome (flower), and PEANUTS!!
> In addition, ground covers include clover and alfalfa. 

Well, to be picky (yes, that means I'm bored):

I think all the garden legumes fix nitrogen.  But it's not true that all 
legumes do.  This family (fabaceae; used to be leguminosae I think) is 
classified by all members bearing their seeds in pods.

Travis

---

From: Dwight Sipler <[email-masked]>
Date: 4 Mar 1996 12:24:30 GMT

>classified by all members bearing their seeds in pods.

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 for legumes used as 
cover crops. Since there are different kinds of bacteria for different 
plants (I am told), there are different inoculants for different plants. 
Check with a farm supply for the right inoculant.

---

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

Travis Saling <[email-masked]> wrote:

>> 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

---

From: [email-masked](Mark & Victoria)
Date: 8 Mar 1996 15:12:52 GMT

>If it aint broken, don't fix it!
Perfection!  In Texas we have an overabundance of N anyway.  I wish
someone would study the N availability in the soil after our
thunderstorm season, yet to arrive :(

Lightening also fixes nitrogen.  And boy do we get lightening here!
A northerner moves south, and instead of the gansters, we have
tornados!  At least the latter is organic!

Victoria*

---

From: [email-masked] (SKID Photography)
Date: 8 Mar 1996 12:17:46 -0500

>tornados!  At least the latter is organic! 
Studies have been done with regards to the availability of N caused by
lightning.  We unfortunately cannot cite specific references, but the gist
of the results were that usually, the rain that almost inevitabley follows
or accompanies the lightning, washes away the N produced by said
lightning.......a complete wash, as it were. 
 
Bill & Harvey 
zuffalig/SKID  zone 6  CT  U.S.A.

---

From: [email-masked] (Gad Zukes!)
Date: 9 Mar 1996 01:43:28 GMT

In <[email-masked]> [email-masked] (SKID
>zuffalig/SKID  zone 6  CT  U.S.A. 

Hi guys - I have just got to say - "to heck with the studies"! I have
gardened in the high altitude desert for close to 20 years. We get 13
inches annual precipitation. In the summer, we get it in the form of
intense thunderstorms. The next day, the corn is darker green, more
robust and bigger. All the plants look better, are bigger, darker
green, etc. I have to believe that the sky rains fertilizer! To heck
with the studies... I'm gonna believe it anyway! And as far as the
storms in Texas - perhaps that explains why everything's bigger! in
Texas!  Julie

---

From: [email-masked] (SKID Photography)
Date: 10 Mar 1996 13:29:16 -0500

>storms in Texas - perhaps that explains why everything's bigger! in 
 
Dear Julie, 
 
Just because there is a thunder (lightning) storm it does not actually
follow that it is the lightning which is causing the 'greening'  You also
mentioned that it rains......perhaps, and I'm not saying this is for sure,
the 'greening' is just caused by the rain. 
 
In the East, at essentially sea level, when it rains a lot, the 'grass'
(and corn is a grass) gets 'greener' and grows A LOT!  In this part of the
counrty, our rains, most often, are not accompanied by thunder and
lightning, and yet the grasses and veggies get greener anyway.  It could be
that the limiting factor in growth, at those times, is just available
water, plain and simple. 
 
We write this not to burst a romantic bubble, but rather so we can all move
ahead with better gardening techniques. (Unfortunately, at the moment we
can't come up with a false 'cause and effect' old wives tale...thinking
that the world was flat, did not seem appropriate.)  If it really is water
that is limiting plant growth, then the next logical step is to try and
figure out how to make water more available to our plants (mulch, soil
ammendments, irrigation etc.)  If it really was the lightning, perhaps we
should do as some other postee suggested (and we think is totally
ridiculous) put iron rods in the soil to attract the electricity in the air
to free up that nitrogen! 
 
Well that's about it........I hope this was not too serious a response to a
lighthearted post. 
 
Bill & Harvey

---

From: [email-masked] (B.K.)
Date: Tue, 12 Mar 1996 06:00:42 GMT

Since plant roots must come in contact with nutrients for them to
become adsorbed, maybe the rainwater is leaching the soil nitrates so
that the nitrate then comes in contact with the root hairs?  This
would explain the greening-up the next day.

B.K.

---

From: [email-masked] (Gad Zukes!)
Date: 5 Mar 1996 00:29:41 GMT

Dwight Sipler <[email-masked]> writes: 

I think all the garden legumes fix nitrogen.  But it's not true that
all legumes do.  This family (fabaceae; used to be leguminosae I think)
is classified by all members bearing their seeds in pods.

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 for
legumes used as cover crops. Since there are different kinds of
bacteria for different plants (I am told), there are different
inoculants for different plants. Check with a farm supply for the right
inoculant.
Hi - If we are going to pick nits here, I'd like to point out that the
bacteria that fix nitrogen from the air in the soil (rhizobia) need the
legumes to supply energy. The rhizobia actually infect the plant. The
whole thing is a lovely symbiotic relationship, so it's sort of like,
which came first, the chicken or the egg. As far as inoculant is
concerned, many seed suppliers also sell different varieties of
inoculant. One you've grown a nitrogen-fixing legume in an area of the
garden, it doesn't have to be re-inoculated for a few years. The other
thing I'd like to say is that I've used the "garden" variety inoculant,
not the specialized stuff, in my home garden for years with great
success. Sometimes this kind of specialization and nit-picky discussion
scares away otherwise enthusiastic beginners. Gardening doesn't have to
be complicated...some people like to make it that way, and enjoy it,
but not everyone has to. Julie

---

From: Dwight Sipler <[email-masked]>
Date: 6 Mar 1996 13:56:39 GMT

[email-masked] (Gad Zukes!) wrote:
>I'd like to point out that the
>whole thing is a lovely symbiotic relationship...........

Thanks for the clarification. My main point was that the bacteria are 
necessary for the nitrogen fixation and not just the plant.

>One you've grown a nitrogen-fixing legume in an area of the
>success............

Good point. I usually use the cover crops in different areas in different 
years, so I usually use the inoculant. It's not expensive, but there's 
always something else to spend money on so..........

>Sometimes this kind of specialization and nit-picky discussion

I didn't mean to scare anyone away. My apologies.

For the new gardner, note that the plants will grow without the bacteria 
if nitrogen is available from the soil, so you don't have to inoculate the 
planting. The advantage in doing so is that more nitrogen will be 
available for succeeding crops in that area.

---

From: [email-masked](Mark & Victoria)
Date: 6 Mar 1996 23:08:28 GMT

>>but not everyone has to. Julie

Using an innoculant with peas or legumes is not a specialized nit pick!
If the bacteria is not available in the soil, (which it usually is) it
has to be put there.  Good gardeners who know their stuff are not nit
picking, they are honing as they learn more and more about soils and
plants.  Depending on what one grows, some of this information is key. 
If a new gardener is planting legumes to fix nitrogen because they read
or heard it somewhere, but they missed the part about the innoculant,
they might not be fixing as much nitrogen as they could had they read
this and other posts.
Victoria*

---

From: [email-masked] (Marion Margoshes)
Date: 6 Mar 1996 22:27:09 -0500

>available for succeeding crops in that area.

Please don't apologize for a scientific answer.  Beginning gardeners 
should read and absorb on their own level, and this will result in more 
knowledge for all.  It would be too bad if this group was kept on the 
lowest level. mbm

---

From: [email-masked] (Mariann Davis)
Date: Thu, 07 Mar 96 16:11:55 GMT

Dwight Sipler <[email-masked]> wrote:
___
___For the new gardner, note that the plants will grow without the bacteria 
___if nitrogen is available from the soil, so you don't have to inoculate 
the 
___planting. The advantage in doing so is that more nitrogen will be 
___available for succeeding crops in that area.

  "available for succeeding crops" ? 

Uh oh. I'm confused. Could one of you knowledgable posters correct my 
misimpressions please? 

I thought that the bacteria allowed the plant to use the nitrogen from the 
air, not the soil, so that's why nitrogen-fixers could successfully grow in 
nitrogen-poor soil. Right so far? 

But, the soil *remains* poor in nitrogen unless the nitrogen, which came 
>from  the air but is now in the plant's tissues, is somehow returned to the 
*soil* by letting the plant return _itself_ to the soil by rotting. The 
plant does not somehow "excrete" (for want of a better term!) into the soil 
the nitrogen it has acquired, does it?  So therefore, grow a legume, at the 
end of the season, rip out the dead plants and put them somewhere else 
(compost bin or landfill, whatever), and you have not done one good thing 
for that soil???!  Correct or not?   Similarly, plant a non-legume cozily 
next to a legume in nitrogen-poor soil, and the non-legume will STILL need 
nitrogen amendments to grow well. Correct or not?  

Side issue: 
So why is planting legumes touted as (it always seems to me) such an 
earth-friendly thing to do?  Analogy: plant a low-water plant, it will make 
your soil wet. No, the low-water plant is merely capable of surviving in 
those conditions, it doesn't change the conditions. Am I totally off-base 
here?

Thanks, you biology/botany/chemistry mavens!!!

.................................................................
:  Mariann Davis                      Egg Harbor, NJ             :
:  [email-masked]            (Pine Barrens country)      :
.................................................................

---

From: Travis Saling <[email-masked]>
Date: Thu, 7 Mar 1996 14:57:04 -0800

> nitrogen-poor soil. Right so far? 

Yes.

> nitrogen amendments to grow well. Correct or not?

The main problem I see in your argument is this:  Why do you assume when
you rip a plant out of the ground, that anywhere near a majority of the
root system comes with it?  The part of the roots that come up with the
plant in this case is the older, woody, essentially non-functional (except
as ductwork) section.

If you turn under a legume, you certainly will release more nitrogen than
if you remove the tops.  But in either case, the largest share of "fixed"
nitrogen is in the root system, most of which remains in the ground when
you pull up a plant.

Travis
Sumner, Washington

---

From: [email-masked] (Allyn Weaks)
Date: Thu, 07 Mar 1996 15:00:29 -0800

>nitrogen-poor soil. Right so far? 

Right, the bacteria take nitrogen from the air in the soil pores, and
convert it to nitrogen compounds that the plants can use (such as ammonia
or nitrates), in return for a cozy home safe from predators, and some
other services provided by the plant.

>*soil* by letting the plant return _itself_ to the soil by rotting.

Ah, but those bacteria are efficient little beasties and don't know when
to stop; they produce more nitrogen compounds than the plant can use.  The
excess appears in the soil, and can be used by other plants.

As Dwight pointed out, if there is already plenty of soil nitrogen
available, there's no need to innoculate with bacteria: many (most?)
legumes aren't willing to 'pay' for a service they don't need, and often
won't bother to negotiate with the bacteria even if they are present.

>the nitrogen it has acquired, does it?

I don't know the mechanism, so I don't know if it's intentional excretion
>from  the nodules, or more like leaching.  But the plant has nowhere to
store the nitrogen compounds except in new tissue, and it's already
growing as well as it can. With a plentiful suply of nitrogen, it's growth
will be limited by something else, maybe a trace element in short supply,
maybe water, maybe light.  So the excess nitrogen does get 'lost' to the
soil.

>Similarly, plant a non-legume cozily 

A heavy feeder such as corn or asparagus is probably going to need more
than just a legume's nitrogen-fixing excess.  But turf grass can easily
live off of the excess from some white clover in the lawn, as long as you
don't expect the currently popular unhealthily lush dark green all summer
long.  In the Pacific Northwest, we have very nitrogen-poor soils on the
average because of the steady winter rains, and red alder, a nitrogen
fixing pioneer tree, is a very important source of nitrogen to get the
ecosystem restarted after a disaster such as fire or clearcutting (though
the loggers don't bother with succession, they just air drop huge
quantities of fertilizers instead).

>earth-friendly thing to do?

Well, in the sense of being a cover crop, they do more than just add
nitrogen.  Some also have deep root systems that help break up and areate
the soil, they help crowd out weeds, and when they are dug in as a green
manure, they add not only the additional nitrogen in their corpses, but
organic matter as well.  The nitrogen fixing isn't usually the most
important benefit of a green manure, but it's a useful enough added bonus
that many people prefer to choose legumes.

>  Analogy: plant a low-water plant, it will make 

Unfortunately, simple analogies often don't work in complex systems, which
is what any sustainable environment is.  Comparatively little is known
about soil organisms and how they interact compared to what is probably
there to be found out.  Legumes are pretty well studied largely because of
their economic importance.
-- 
Allyn Weaks
[email-masked]
PNW Native Wildlife Gardening:  (under construction)
  http://chemwww.chem.washington.edu/natives/

---

From: [email-masked](Mark & Victoria)
Date: 8 Mar 1996 15:08:55 GMT

Legumes are pretty well studied largely because of
>their economic importance.

Allyn what do you think of the ammendment in the Texas Consitution
which allows ag land to be used for wildlife refuge, not farmed, yet,
still allows the tax break?  I think it is a wonderfully progressive
statement which more states should follow.  It is in it's infancy
currently, but the Extension and Comptroller etc are working together
to better the ecological environment in Texas.
Victoria*

---

From: [email-masked] (Allyn Weaks)
Date: Sun, 10 Mar 1996 22:56:39 -0800

> still allows the tax break?

Sounds good.  And I've heard a rumor that Colorado has tax credits for
people who actively improve habitat.
-- 
Allyn Weaks  [email-masked]
PNW Native Wildlife Gardening:  http://chemwww.chem.washington.edu/natives/
Any advertisements sent to any of my email accounts will be billed $25 per
message, $1 per character, including all header lines.  No exceptions.  Sending
such mail constitutes agreement to these terms.

---

From: [email-masked] (Gad Zukes!)
Date: 8 Mar 1996 04:56:57 GMT

In <[email-masked]> [email-masked]
>Dwight Sipler <[email-masked]> wrote:
___
___For the new gardner, note that the plants will grow without the
bacteria 
___if nitrogen is available from the soil, so you don't have to
inoculate 
the 
___planting. The advantage in doing so is that more nitrogen will be 
___available for succeeding crops in that area.

Mariann wrote: 

I thought that the bacteria allowed the plant to use the nitrogen from
the air, not the soil, so that's why nitrogen-fixers could successfully
grow in nitrogen-poor soil. Right so far?  

Yes.
But, the soil *remains* poor in nitrogen unless the nitrogen, which
came from the air but is now in the plant's tissues, is somehow
returned to the *soil* by letting the plant return _itself_ to the soil
by rotting. The plant does not somehow "excrete" (for want of a better
term!) into the soil the nitrogen it has acquired, does it?  So
therefore, grow a legume, at the end of the season, rip out the dead
plants and put them somewhere else(compost bin or landfill, whatever),
and you have not done one good thing for that soil???!  Correct or not?

Incorrect.

Similarly, plant a non-legume cozily next to a legume in nitrogen-poor
soil, and the non-legume will STILL need nitrogen amendments to grow
well. Correct or not? 

Incorrect, although if the soil is really poor, it might need more
nitrogen added to soil.

Side issue: 
So why is planting legumes touted as (it always seems to me) such an 
earth-friendly thing to do?  Analogy: plant a low-water plant, it will
make your soil wet. No, the low-water plant is merely capable of
surviving in those conditions, it doesn't change the conditions. Am I
totally off-base here?
>Thanks, you biology/botany/chemistry mavens!!!
................................................................
>:  [email-masked]            (Pine Barrens country)      :

Julie writes:

Here is a quote from Rodale's Encyclopedia of Organic 
Gardening (c. 1968): "An acre of inoculated legumes will take as much
nitrogen from the air as is contained in ten tons of manure. Much of
this is stored in the soil, and much or all of the rest is returned to
the soil when the plants or their residues are plowed down" (p. 663) 

It is known that legumes fix nitrogen from the air and add it to the
soil, as well as using it for their own growth. That is why growing
corn and beans together worked so well for American Indians...the beans
added more nitrogen to the soil, which the nitrogen hungry corn could
use.

I want to reply to a few remarks As far as my concern that sometimes we
get carried away - for example, with specialized inoculants for legumes
- and "scare" away potential gardeners... 1) I am a long time "how to"
garden writer and know from experience how this turns off a
beginner.While I do discuss "scientific" bases of the many aspects of
gardening, I also let readers know that they can keep it simple and
still be successful. I also didn't intend for the author of the
information about the legume inoculants to apologize. His info was good
and accurate...I was just adding a few thoughts.

2) I did not mean to imply that this type of specific information
should not be discussed or shared, simply that less complex
alternatives be given, too, to help beginners have a successful,
uncomplicated first or second garden 

3) if I were a beginning gardener, I would resent the attitude that was
expressed in one post replying to mine that less scientific information
is somehow "lower" than more specific, more scientifically exacting
discussions. I think there's room for everyone here. It would equally
be a shame if this group became the domain of "hi-falootin'" elitist
plant people...the beauty of this group is that we can all get
information we can use and we can ignore those discussions/topics that
are of little use or interest to us.

---

From: [email-masked] (Mariann Davis)
Date: Fri, 08 Mar 96 14:54:26 GMT

----------------begin original message-------------------------
In article <[email-masked]>,
   [email-masked] (Gad Zukes!) wrote:
Julie writes:

----------------end original message-------------------------

Julie/lizard3/Gad Zukes,
 
Thanks for your response. Your quote agreed with my point: 
"..much or all of the rest is returned...when residues are plowed down."
(Although it seems like unclear writing to say "much is A, and much or all 
of the rest is B", don't you think?)

The two statements I want to know more about are: 
1st paragraph (Rodale):  "Much of this is stored in the soil,"
2nd paragraph (you):     "and add it to the soil,"

This does sound like the plant is secreting or excreting the nitrogen into 
the soil. How does it do this?  Does it then follow that over a period of 
time, the nitrogen in the soil will build up to a more normal level (in 
soils that started out nitrogen-poor, then legumes were planted)? 

Mariann
not a biochemist, nor do I play one on TV

---

From: [email-masked] (Gad Zukes!)
Date: 9 Mar 1996 16:01:46 GMT

In <[email-masked]> [email-masked]
(Mariann Davis) writes: 

<<<large snip>>>
-------- original post from Mariann Davis -------------------
>This does sound like the plant is secreting or excreting the nitrogen
>into the soil. How does it do this?  Does it then follow that over a
>period of time, the nitrogen in the soil will build up to a more
>normal level (in soils that started out nitrogen-poor, then legumes
>were planted)? 
>
>Mariann

Hi Mariann - Sorry that I was not more clear. The rhizobia that
colonize the roots of legumes don't inject the nitrogen into the plant.
As far as I understand, it just changes atmospheric nitrogen into an
ion that the plant can take up from the soil. Apparently, the bacteria
are so efficient, the legumes don't use all of this ionized nitrogen,
so the nitrogen remains in the soil...held there by other chemical
reactions with the soil particles. So that is how legumes actually
"add" nitrogen to the soil. Certainly leaving the roots to decompose in
the soil adds more nitrogen (and other nutrients and organic matter),
the same thing with turning top growth into the soil (which is what you
do with a cover crop). I am not a biochemist either, but learning about
how soil works is fascinating, plus I think it made me a better
gardener (I studied it years ago). If you can find the textbook "The
Nature and Properties of Soils" by Nyle C. Brady (I think - I can't
find the book right now!), it's worth the read! Julie

---

From: [email-masked] (B.K.)
Date: Tue, 12 Mar 1996 06:00:39 GMT

>>Marianne wrote:
>>the soil. How does it do this? 

The plant itself does not fix nitrogen.  It is the nitrogen fixing
bacteria which you seem to be in question of.  These organisms have a
symbiotic relationship with leguminous crops, and a few others. They
live in root nodules(those black balls on the legume roots).The
bacteria fixate atmospheric nitrogen(around 75% of the plants N needs)
and provide it to the plant, and the plant provides
nutrients/environment for the bacteria.  

Using legumes as a Companion Crop:
Though some nitrogen is excreted into the soil, probably by excreting
amino acids and nitrogenous compunds, grazing or cutting off the plant
tops will release nitrogen into the soil and make it available for the
companion crop.  Other nitrogen can be released by small pieces of
root which die off and decompose.

For Crop Rotations:
The entire legume can be tilled into the soil at the end of its'
growing season.  The soil microbes decompose the plant into nutrients
which become available to the following crop.  

Hope that helps.
B. K.

---

From: [email-masked] (Dave Platt)
Date: Wed, 13 Mar 1996 23:20:46 GMT

>the nitrogen it has acquired, does it? 

There's probably a small amount of excretion of fixed nitrogen, but I
understand it's only a small fraction of the amount actually produced.
The majority of the fixed nitrogen is used by the plant, in its leaves
and stems during the early portion of the growth season and then in seed
production.

>                                 So therefore, grow a legume, at the 

Basically correct, I believe.  Some amount of fixed nitrogen will remain
in the root nodules that are left in the ground after the legume is
harvested, and this will enter the soil as the roots rot away.

Legumes can be very good for the soil, nitrogen-wise, if you use them as
a "green manure".  Plant 'em, let 'em grow, and then before they set
seed, plow them under.  During the growing season, they'll help hold the
soil in place (reducing wind and water erosion, keeping the soil cool,
and encouraging the growth of a good ecology of soil microorganisms).
Once they've been plowed under, they'll decompose, returning the fixed
nitrogen in their roots and stems and leaves to the soil.  Fava beans
and alfalfa are often used in this way.
-- 
Dave Platt    [email-masked]
      USNAIL: The 3DO Company, Systems Software group
              600 Galveston Drive
              Redwood City, CA  94063

---

From: [email-masked] (John Atkinson)
Date: Mon, 11 Mar 1996 14:01:47

In article <[email-masked]> [email-masked] (Gad Zukes!) writes:

>In <[email-masked]> [email-masked] (Bryan Cort)
>writes: 
>>>Bryan Cort
>>[email-masked]

>In addition, ground covers include clover and alfalfa. 

Also, casuarinas (sheoaks etc) fix nitrogen.  In the New Guinea 
highlands they were planted for this reason (to reinvigorate wornout 
soil), the same as legumes are elsewhere in the world (also presumably 
for firewood).  But they're no use for food and their flowers are 
pretty insignificant, so they'd be no good for you Bryan.

John

---

From: [email-masked]
Date: Fri, 08 Mar 1996 01:32:31 GMT

>[email-masked]

All plants of the family Leguminosae (Peas, beans, etc.) will fix
nitrogen if the soil is lacking in it.  Other good examples are
clover, mimosa (sensetive plant), acacia, and tropical Poincianas.
Good luck.