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getting the salt out of soil  RSS feed

 
paul wheaton
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Location: missoula, montana (zone 4)
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I don't have this problem, but I seem to be bumping into people that do have this problem.  And I'm also getting more curious about it as I explore the ideas of people peeing their salty pee all over the farm.

During lunch at a recent workshop, erica wisner put a blue dot on a piece of tissue then dipped the bottom of the tissue in water.  The blue went up as  the water wicked up.  This was to demonstrate how arid lands have so much salt in their soil.  I guess the blue dot represents the salt. 

But ... supposing there is only five inches of rain per year - the rain would land on the top of the soil.  So some of the salt would washed down, and some would be wicked down.  Granted, some water would sneak through paths to get lower and then get wicked up. 

Next, (and this could be the answer) If the soil is barren, then eventually the stuff on the top will dry up, thus leaving water down low which gets wicked up to the surface to dry out. 

But I guess it seems like, at worst, the soil will stay about the same level of salty.  And even with as little as five inches of rain per year, a lot of that probably happens in a one week event which, I would guess, would move most salts down to the groundwater.  Especially with one rainy week a year for thousands of years.

Not so?



 
Joel Hollingsworth
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You mention deflocculation briefly in your lawn care article.  It plays an important role in salt buildup, if I recall correctly.

From what I remember, as the level of salt builds up locally, it eventually reaches a tipping point where the surface interactions with the soil change drastically, and the soil begins to reject that salty water.  The extra-salty water is then able to move into nearby soil, which had been near the point of deflocculation, and a chain reaction destroys a lot of tilth quickly.

I think real problems arise from water that flows near the surface, especially irrigation water but maybe also rain that flows downhill within the property before evaporating.  I bet there are good books on the subject.

I could imagine keeping saltwater fish and asparagus in a brackish aquaponics system at the end of one's waterworks, and harvesting salt from that water Gandhi-style every so often.
 
Leah Sattler
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http://soils.usda.gov/sqi/publications/files/Salinzation.pdf

I thought salinization of the soil was often associated with irrigation. ie growing things in places that simply don't have the natural rainfall or natural soils created by years of that rainfall to support agriculture.  my very elementary understanding  was it was usually caused by basically shallow watering, slow drainage and quick evaporation. I don't think 5 inches once a year in soil that otherwise gets no rain is going to carry the salt very deep.
 
paul wheaton
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So rainwater mostly passes between the cracks in the soil to go down deep and then it gradually wicks back up - thus bringing the salt with it.  Yes?

 
Joel Hollingsworth
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Edit: removed bad info.
 
Leah Sattler
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this author explained it they way I understand it and more clearly than I. although keep in mind that there can be several reasons for salinization of the soil. like watering with sea water (uhm...duh) and probably other more technical reasons.

"The build-up of salts at or near the surface of a soil. In hot, dry climates, evapotranspiration exceeds precipitation, so that surface water evaporates rapidly. This causes the soil moisture, together with its dissolved salts, to come to the surface by capillary action. This water then evaporates, leaving behind a crust of salts on the surface. This process occurs naturally in desert soils, but the incorrect use of irrigation in arid lands can cause salinization"
http://www.answers.com/topic/salinization
 
                              
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I just have to say salt crystals are pretty cool--my sister has a cluster of salt crystal the size of a grapefruit she brought home for Africa. There is a little spot she lets us lick
 
paul wheaton
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And there is the key:  "evapotranspiration exceeds precipitation"

Wikipedia has a freaky pic:  http://en.wikipedia.org/wiki/Soil_salinity

 
Leah Sattler
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wow that is a freaky pic! it looks like snow! I can't imagine trying to grow anything there.....
 
Gwen Lynn
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Yeah, if I had to guess, I would have thought it was snow. Pretty wild!
 
Joel Hollingsworth
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Leah Sattler wrote:
I can't imagine trying to grow anything there.....


Prawns?

Edit:

The more I think about it, the more I imagine my strategy for land like this would be:

Make the most interesting-looking part of it a scenic resort, with some museum- or park-style exhibits on salinization.

Integrate a salt-tolerant aquaponics system with some natural swimming facilities, in a greenhouse-like area.  Wax myrtle would be a useful part of this.  Take some care against contamination for any food production...but fish, shellfish, asparagus, Warrigal greens might be good here.  Route the exhaust through a long cool underground pipe with a means of gathering condensation, so that the whole thing functions as a still.  Have shallow sun-heated trays to dry out brine or ag products, that the exhaust system can draw from on days when the greenhouse needs to maintain its temperature.  The exhaust can be driven by a solar chimney.

Scrape up the salty crust in less-beautiful places, and do a little processing to purify it for sale (more on that later).  Plant drought-tolerant aromatic plants like lavender and thyme over most of that space.  Some prickly-pear and agave.  Maintain a small set of raised beds in a chicken moat to help feed the resort-goers.  Include some flowers and gourds.  Be extremely careful to drain all of this into the aquaponics system.

Sell bath salts, exfoliants, "sisal" bath scrubs (actually of blue agave fiber, but no one has to know), candles, potpourri, dry snack food, dry flower arrangements, etc. in the gift shop, and online.
 
Leah Sattler
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polyparadigm- you are truly creative! I think  would just cry if I was told I had to make something of that place but i couldn't begin to handle a resort type place....too many people to have to mingle and smooshge with.
 
                                  
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In the geoff lawton video about reclaiming the desert in Jordon (available on YouTube), at one point some agronomists from the local university come out and express fear that Lawton's irrigation will salinize the surface and also flush salt into the underground water, thereby contaminating it.  But by mulching and swaleing, Lawton claims that he prevented that from happening.

Also, I think in the video, it is mentioned that as the desert soil becomes enriched from mulching and swaleing, and proper drip irrigation, the salt level does not necessarily diminish but the crystals become isolated, inert, inactive, coated, locked up, suspended, whatever the correct term is, and are no longer harmful. 
 
j cornelissen
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here in Australia salination of the soil is a massive problem.

it is caused by deforestation of the land and subsequent reduced water usage. Fewer trees, less water uptake and hence rising ground water. The rising ground water levels bring up minerals (salt) to the surface making the pastures infertile.

the solution is lowering the ground water levels, this is done by pumping up water (not ideal) or planting salt-tolerant deep-rooted plants / trees like saltbush (excellent stockfeed for nice tasting lamb) and alfa alfa

ironically, we're dealing here with drought as well as rising water levels (i don't think we could have screwed things up more if we tried)

Jan
 
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