[permaculture] N in arid soil
jackrowe at tinyorb.net
Fri Dec 18 12:21:10 EST 2009
I have a similar situation in northern New Mexico, US, as regards
low soil moisture -- low precip, high evap. We try and keep our
mulches replenished (materials are not overly plentiful because
of the aridity) and rather than composting in piles, we put all
materials on the garden as mulch. A lot of N is released by the
mulch during its breakdown/composting process, if this happens in
place on the soil the N will be taken up by microbes to a very
large extent (this is true in humid climates as well, though
muches need to be added more often and in thinner layers to avoid
waterlogging). No doubt some N is 'lost,' but the earth being a
closed system (if we include the sun and ignore meteorites/dust)
the N will be used somewhere by some grateful plant. Nothing is
'lost' on our planet, this is the big problem w/ how we 'dispose'
of the things we don't like -- it's a shell game where all the
shells get smothered in poop while the gardens go hungry.
We also store water in ferro-cement cisterns in an attempt to
have water to keep the soil moist during the dry season to the
degree possible. And we accept that plants will be tending toward
some dormancy during the dry period (which for us occurs in
spring, not 'convenient' from a gardening point of view, but w/ a
little help the plants bide their time until the water comes).
Using drip under the mulch minimizes evap and also minimizes
salt-buildup, which is a perennial problem in arid soils and
difficult to fix once it happens. Here again rainwater is very
valuable as it contains no salt; gypsum (calcium sulfate...
sulphate?) helps release the salt which is otherwise very tightly
held by ionic bonds in the soil (assuming presence of clay and/or
ANY salt in the soil (free or bonded) exerts an osmotic pull on
the soil's water, making it that much more difficult for plants
and microbes to use this water. Even when gypsum releases the
sodium ions, it's hard to find enough water to wash the salt away
and it continues to exert its pull on soil moisture. If you're
using well water, this problem is a virtual certainty. I've seen
salt shut down a soil in 3 - 4 years, esp. when greywater is
included (extra salt from several sources including urine, bodies
being washed, cooking). Greywater should always be applied
sub-surface in arid areas, if it is used at all. We put our
greywater into a basin planted to salt-loving trees, in our case
Siberian elms, well-hated but good mulch producers, kept 100 feet
from gardens they are useful (very aggressive roots).
And pardon me for saying so (just in case you're squeamish), but
if you're willing to pee in a bucket you can keep a substantial
amount of garden area well-supplied w/ soluble N (1 pee: 15 - 20
water or about a quart per 5-gallon bucket, this ratio will vary
w/ how much water you drink) and a happy dose of K as well. The
soluble N in urine will be available to soil microbes and plants'
roots even when the general microbial population has slowed
nutrient cycling due to dry conditions. Using urine, you will add
slightly to the salt problem so extra attentiveness is called for
(this is true for manures as well).
Sorry for the silence on your on-topic post, we've all been
ardently discussing who shall be called Right and who shall be
called Wrong. Me... I'm Wrong, but warm and over-fed, so for some
reason I still have this stupid persistent grin on my face.
----- Original Message -----
From: "Rain Tenaqiya" <raincascadia at yahoo.com>
To: <permaculture at lists.ibiblio.org>
Sent: Wednesday, December 16, 2009 4:17 PM
Subject: [permaculture] N in arid soil
In permaculture, part of our goal is to keep nutrients, energy,
and water cycling within the biological realm as much as
possible. Composting, slashing carbon and dynamic accumulator
crops, and the use of animals in systems are ways of speeding up
nutrient cycling and concentrating carbon and nutrients into our
production systems. During a dry period, the cycling slows down
as organic matter and manures are not able to break down and
return to the system. Unless we apply water to these materials,
they will pretty much remain unused, losing nitrogen to the air,
until it starts the rains return. This is the challenge that I am
concerned about in the Mediterranean climate that I live in.
Short of collecting all the material, composting it in irrigated
piles or pits, and redistributing it, I am resigned to lowered
productivity in my systems, and slower soil building.
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