Re: Soil Crusts "Plan B" versus "Holistic Management"
- Hi Dieter,
The kind of crust I was thinking of is also sometimes called a cap.
We get them around here, in silt/sand/ clay soil . . . The clay and
silt dissolve in water and rise to the surface of the soil, and as the
soil dries out and shrinks, this cap or crust tends to have a layer of
air between it and the rest of the soil. Water does not percolate
through it, but rather runs off it, and this cap or crust can be down
right sodden and the layers beneath will be bone dry. If left to its
own devices it grows algea, and then moss. Animals tramp through it
and break it down, and then water can get through it, and plants grow
. . . . On the other hand, if the soil has enough organic matter, or
an organic matter mulch, the crust or cap never forms . . .
I have lived and gardened in heavy clay soil, and while we had surface
drying, we didn't have this sort of cap or crust form . . .
I haven't tried to dry farm in this stuff personally, but folks around
here do dry farm. The plant before the spring rains end, so that the
plants can root down into our high water tables before the triple
digit heat sets in . . .
Around here folks break up these crusts or caps before the fall rains,
so the soil can soak up the water.
Also, my second husband was/is Indigenous to a region known as the
sand hills of Texas. Down there they hoed their gardens when the
plants started showing signs of water stress. How they described what
they were doing is different than what many other folks describe is
happening when creating a dust mulch. They said they hoed and turned
the top layers of soil to increase evaporation from the soil. The
increased evaporation, as far as they were/are concerned, brought
water up into the plants root zone from deeper layers of soil, by
capillary action . . .
Personally, I am into organic mulch, and plenty of it. But I don't
live or garden in the desert, and I never have.
In any event, it seems as though Lester Brown dosen't know what he is
talking about . . . but maybe somewhere on the planet, what he is
saying is accurate . . .
Thanks for your detailed answer!
--- In firstname.lastname@example.org, "Dieter Brand"
> I don't know any of the authors you mention and I'm not sure I know
> what you mean by "soil crust". If you mean that a crust is forming on
> a clay soil, then it is obvious that such a soil will dry out rapidly.
> The purpose of the "dust mulch" in dry-land farming is to break the
> soil crust and thereby cut the capillaries that feed humidity from
> lower soil layers to upper soil layers until it evaporates at the soil
> surface. In dry-land farming, "evaporation" is reduced to near zero
> by the dust mulch. A mulch of plant residues can never cut
> evaporation to the same degree as a dust mulch. This is one of the
> principal drawbacks of NF in dry areas.
> Plant coverage does reduce evaporation a little; however, this benefit
> is more than offset by the humidity lost due to "transpiration" via
> the plants. Here again the "dust mulch" which reduces competition
> from weeds to zero is superior to a vegetative mulch.
> In a soil with little or no "deep percolation" and no transpiration, a
> dust mulch can conserve almost all humidity for months even at ambient
> temps of around 100 F. This has been used by millions of farmers in
> all arid regions of the World for centuries and has been described,
> among others, by Whitsoe and Steve Solomon.
> In the South of Portugal, the typical rainfall from May trough
> September is ZERO mm at temperatures sometimes topping 100 F in
> August. Nevertheless, farmers are able to grow an admittedly meager
> crop of a corn for dry-land farming (Zorhino) from May to August with
> a dust mulch. With a crusted soil the ground would be completely dry
> within a couple of days. With an organic mulch humidity is preserved
> for a little longer, but far from what a dust mulch can achieve.
> Dieter Brand
> PS: When I hear of plans to Save the Planet or Civilization my mind
> tends to go blank. Too many plans already.
> On 12/21/08, Jeff <shultonus@...> wrote:
> >> I am currently reading "Plan B 3.0, Mobilizing to Save Civilization,"
> >> and I have a number of thoughts on what I am reading . . .
> >> Just last night I was reading the author's (Lester R. Brown) thoughts
> >> on soil crusts. I have just a little experience with soil
> >> that experience shows that they prevent water percolation andincrease
> >> runoff. This is strongly echoed in "Holistic Management" by Allencycles.
> >> Savory, who has far more experience with soil crusts, and has
> >> documented the ways they interfere with revegetation and water
> >>this point.
> >> However, Brown claims that soil crusts conserve water and that
> >> livestock need to be managed to preserve the crusts. I am wondering
> >> if any of you have any experience or thoughts on these matters.
> > I too am very suspicious of all of Lester Brown's work for various
> > reasons. And although I really really disagree and dislike...
> > Lomborg's assessment the things he says about Brown are generally on
> > track (Lomborg Skepitical Environmentalist).
> > Brown has been in the past guilty of manipulating data, and what I
> > consider poor science and scare-mongering and exageration.
> > that being said, much his current stuff is much more reasonable.
> > and it's true that soil crusts do conserve EXISTING soil moisture, and
> > many of them ARE nitrogen fixing algea....
> > the problem with much of the west is not conservation of soil moisture
> > (tall grass does just as good or better with moderate amounts of
> > mulch/duff), the point you have is valid.
> > It limits the sprouting of new vegetation and these soil crusts result
> > in most rain running off intstead of infiltrating.
> > I think that Browns experience might be based on the soil crusts that
> > result after draining rice patties...
> > rather than the soil crusts that develop in arid and tundra
> > situations... they are diffinitley two different bird entirely.
> > one of the other problems I have with Brown is he doesn't put the
> > money where the mouth is...
> > a while back he theorized a ultra-hybrid car that would get extremely
> > good gas mileage... yet he never persued a proto-type to prove his
> > point, and even with the x-prize challenge for 100mpg, he has already
> > move on to other topics.
> > Brown also seems to be outside of how common people live.. too much
> > envolved in the politics of DC, and the political will of the
> > coroporations, ...
> > anyways, although Savory's working examples are few and far between,
> > they do exist and work in the real world...
> > Lester's Brown doesn't have any REAL world solutions that have been
> > implemented successffully despite being around for 40 years at
> > jeff