[Scpg] Chemical nitrogen vs nitrogen fixing plants

[Permacltur at aol.com]

A few comments on the unsigned comments below (possibly from Mark 
Fitzsimmons) are in order.

First, the non leguminous species he mentions as nitrogen fixers are good 
choices. However, they fix nitrogen through the action of Frankia spp., not 
really even bacteria, while legumes support nitrogen fixation by hosting Rhizobia 
spp. and very closely related genera.   I'm under the impression that Frankia 
symbiotes work with decidedly different host families, of which Mr. Fitzsimmons 
(?) mentions two representatives.   However, Rhizobia and their kin are at 
times highly specific.   For example, the nitrogen fixing bacteria that work 
with common beans will not fix nitrogen for soybeans.   For that you need an 
entirely different bacterium.   Some bacteria, such as the species that 
constitutes cowpea inoculant, work with many species.   Lupines require one specific 
bacterium.   And so forth.

Benefits from nitrogen fixation are not as cut and dried as Mr. F. (?) 
suggests.   Some legume species exude nitrogen compounds from their roots while 
growing and roots of all plants go through frequent cycles of growth, dieback, and 
renewal that leaves the organic matter (which will contain fixed nitrogen in 
the case of the plants we are discussing.)   So in those two ways nitrogen is 
made directly available for other plants to forage, though the same plant also 
can take some of it back again as needed.   Mycorhizzal fungi move nitrogen 
between plants, including plants of different species in some cases, and can 
move fixed nitrogen to a non fixer species.   Nitrogen fixers drop leaves during 
the growing season, or are browsed, resulting in release of fixed nitrogen to 
the soil before the plant dies.   We   I lived in Massachusetts, I discovered 
that bean beetle infestations did not much affect the bean crop, but I could 
plant Brussels sprouts between the rows of beans which would be 'released' and 
fertilized as the bean beetles defoliated the bean plants late in the season, 
allowing the Brussels sprouts to shoot up with the newly available light and 
fertilizer (including fixed nitrogen) and make a good last minute crop.   
Since the brassica loves the cold fall weather, frost and all, and the beans die 
with frost, The season for that patch of garden is extended right into early 
winter.   The fixed nitrogen is a part of what makes this possible.   Similarly, 
we have had great success in cooler climates growing tomatoes in a living 
mulch of white clover.   White clover is one   of those legumes that increases 
the rate of nitrogen fixation when browsed (or mown).   I often thought that we 
could grow tomatoes with clover and manage the clover and weeds by fencing 
rabbits, which do not eat tomato plants.   The rabbits would have to be moved out 
before   the tomatoes begin to ripen.   Most animals like ripe tomatoes.   
:-)   However, weaned rabbits cold be raised to slaughter age almost entirely on 
clover and incidental weeds, making the clover fix more nitrogen and also 
returning some nitrogen to the soil as manure.   This is sort of a dryland 
version of the strategy used in the book THE POWER OF DUCK, where ducks and rice and 
azolla are the main species.   (The ducks also control invertebrate pests.)   
I'm wondering why no one is mentioning azolla in this discussion, or, for 
that matter, free living nitrogen fixing bacteria that fix nitrogen using the 
energy released by digesting soil organic matter.

The energy cost also needs to be mentioned.   There is a huge difference in 
the amount of food you can get from a field of soybeans that fixes nitrogen as 
compared, say, to a field of corn.   A part of this difference reflects a more 
efficient photosynthesis method used by corn.   But the main difference is 
the fact that the soybeans use much of the energy they fix from the sun to feed 
their nitrogen fixing bacteria.   Nitrogen requires more energy in most 
compounds than in the N2 of the atmosphere.   (That's why you can make nitrogen 
compounds explode, suddenly releasing that energy.)   If our plants are going to 
produce something related to TNT from stable atmospheric nitrogen, they have to 
supply that energy.   Thus I shake my head when plant breeders try to develop 
a nitrogen fixing strain of corn, so that they can have high yields and free 
nitrogen.   And I wonder what they were doing during high school science 
classes.   You can't have it both ways in a single species, but you can get partway 
there with various polycultures, plant communities.

Regarding boron, one need be painfully careful about introducing this 
compound to the soil.   It is useful in exceedingly small amounts but quite 
phytotoxic in slightly larger amounts.   Organic sources such as seaweed or materials 
grown in boron rich areas are the way to go, or (heresy!) the use of slow 
release chemical fertilizers containing trace elements, such as Osmocote plus.   

Looking at fertility, we need to remember that most of these fertility cycles 
are short circuited by commercial agriculture, where nutrients are exported 
to end up as food, flushed after going through people, into something that 
becomes water pollution, or as waste ending up in the landfill.   Those of us with 
a private land base can address the first waste.   The waste of food can be 
addressed by feeding food wastes (instead of primary grain production) to 
livestock.  Again, this can be a way to return some of the nitrogen, etc., directly 
to the soil, as manure.   For a number of years when I lived in 
Massachusetts, I moved my homestead hogs to the garden after harvest, to finish them there. 
  This is the period when they eat most and so produce most manure.   (and 
they destroy all cutworms, slugs, grass stolons, etc., and clean up most crop 
residue.)   At present, we have plans to set up a similar arrangement in Florida 
where we now live, using an old corral as the basis for a pen.   The previous 
owner planted an oak tree in the center of the corral, which is now large 
enough to provide the requisite shade, and which will soon be producing crops of 
acorns that pigs love.  We will alternate use of this fenced area with a 
garden, free of pernicious grasses and other weeds, fertilized, and ready to plant. 
  Prior to getting new feeder pigs, we will plant feed crops in their same 
garden, greens, root crops such as chuffa, etc.    All the food wastes we bring 
to our pigs will help build the soil, and much of the nitrogen, etc., will 
cycle round and round. From pigs to oaks to acorns to pigs, for example.   

What we need to be looking at is a lot of ways to conserve, recover, and fix 
nitrogen and not just one approach.   Since 'chemical' nitrogen is fixed using 
fossil fuels, the price will in rise to the point where people either adopt 
such strategies or protein rich food will be inaccessible to even more people.

Dan Hemenway


In a message dated 6/11/08 8:51:00 PM, Mark.Fitzsimmons at pwr.utc.com writes:


> This discussion got me to do some researching on plants I can use to
> increase N in my soil (I just recently sheet-mulched the entire yard
> except for compost and garden and need to keep the nitrogen up). I have
> a bunch of legume seeds I can use for the purpose, however most of the
> nitrogen they fix is only available when plowed under. I will plant
> clover under my fruit trees to see if it helps. I also found several
> local native plants fix nitrogen due to the poor soil in the nearby
> mountains: Alder trees and ceanothus for example make associations with
> nitrogen fixing organisms in the roots. Ceanothus will make N available
> to plants while alive, probably aiding in regrowth after fires, and bees
> also like it, so I may plant some of that in my yard next to a fruit
> tree and see how the flavor of my honey changes. I suspect, from
> observing bees in the forest, that the honey they call "sage" is really
> mostly ceanothus nectar. http://en.wikipedia.org/wiki/Ceanothus
> 
> Does anyone know where I can get myrica rubra seeds or seedlings? This
> is another high antioxidant fruit that looks intriguing and has
> symbiotes that fix nitrogen.
> 
> I suspect it may be necessary if growing some of these from seed or from
> a nursery to dig up some root nodules from other N-fixing plants to
> inoculate the soil of a new plant.
> 
> The problem of K and P don't seem so bad to me if one continues to use
> phosphate containing soaps and uses grey water to move it into the yard.
> Phosphates in soaps are only a problem if the water is going to the
> ocean, but the reason it's bad is the same reason it's good in your
> garden: plants love it!
> 
> Many soaps also contain potassium, especially industrial cleaners, so
> toss your soapy water onto the compost pile. I grey water my kitchen
> sink including dishwasher and the grape vine growing next to it is HUGE
> and healthy.
> 
> Also, these elements are in all biological organisms, so the more you
> compost, including fat and bones, the more you are putting back into the
> compost heap. I don't agree at all with the popular concept that bones
> do not belong in the compost pile. I put all my meat scraps in the
> compost. As long as you bury it, there is no problem. I am happy to see
> chicken bones from years past, now soft and spongy and falling apart, as
> I dig through my garden. Who needs to buy bone meal? Use bones!
> 
> Boron is another important TRACE element, especially for woody plants,
> and it also is a safe method of killing ants, termites and fungus, but
> be careful you don't kill the symbiotic fungi in plant roots, or the
> plants themselves!! If you use it and nearby plants' leaves begin dying
> at the edges, stop.
> 
> >From Wikipedia:
> Boron is an essential plant nutrient, required primarily for maintaining
> the integrity of cell walls. Conversely, high soil concentrations of >
> 1.0 ppm can cause marginal and tip necrosis in leaves as well as poor
> overall growth performance. Levels as low as 0.8 ppm can cause these
> same symptoms to appear in plants particularly sensitive to boron in the
> soil. Nearly all plants, even those somewhat tolerant of boron in the
> soil, will show at least some symptoms of boron toxicity when boron in
> the soil is greater than 1.8 ppm. When boron in the soil exceeds 2.0
> ppm, few plants will perform well. Plants sensitive to boron in the soil
> may not survive. When boron levels in plant tissue exceed 200 ppm
> symptoms of boron toxicity are likely to appear.
> 
> I mostly use borates (US Borax product Tim-Bor)to kill termites and
> fungus in wood I am cutting up, but one could use it or borax to keep
> down aphids on plants with a spray bottle, though regular
> phosphate-containing soap is probably better for the garden. For
> example, I tried it on artichokes and I don't think they liked it, but
> the roses seemed to tolerate it well.
> 





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