[permaculture] N in arid soil

Jack Rowe jackrowe at tinyorb.net
Fri Dec 18 12:21:10 EST 2009


Rain,

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 
humus).

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.

Jack

----- 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.

Rain



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