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Subject: Healthy soil and sustainable growing

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  • From: "Douglas Willhite" <drwillhite@earthlink.net>
  • To: "Douglas & Hillary Willhite" <drwillhite@earthlink.net>
  • Subject: [Livingontheland] soil fertility
  • Date: Sun, 3 Jun 2007 10:51:56 -0700

In my years as an agriculture teacher, a science teacher, and a farmer, I've
noticed a great deal of misinformation out there about animal manures and
compost. Many believe that you can turn a few animals out in a pasture and the
animals, by means of their manure, will make the soil more fertile without any
help from the feed store. .

And when it comes to compost, magical qualities are sometimes attributed to it
that can't be supported by the laws of science. A popular book by John Jeavons,
"How to Grow More Vegetables . . . ", advocates growing "compost crops" on
garden beds, composting them, and then returning them to the beds with the
expectation that soil fertility will be sustainably enhanced. For years I've
let the idea of a "closed system" slide without challenge but at this point in
time I feel compelled to come out of the closet. As we know, grim times may not
be far ahead and gardeners who anticipate getting a good portion of their food
from their gardens need to be working with a full-deck of information.

Whole systems agriculture advocates an "open system" to build and maintain
fertile soil. The principal vehicle for this, in a post-carbon world, would be
to gather mulch from land surrounding one's garden and bring it into the garden
for mulching the beds. My very rough calculations for the amount of land
required for this go like this. . .

--1/10th acre of intensive bed will supply the subsistence caloric requirement
for 1 person, harvesting 2 crops per year. 1/5th acre would be required if the
climate is such that only one crop can be grown.

--Fertility would be enhanced and maintained by gathering mulch from an
additional 1/10 acre to one acre of less intensively used land, say from urban
and suburban landscapes, pastoral or wildlands.

Let me review the scientific principles that apply here. . ..

We have, in the first place, the Law of Conservation of Matter. This says that
matter, and more specifically elements, cannot be created or destroyed [at least
in one's backyard] and that matter can only be reorganized into various
compounds. This means that nothing comes out the back of an animal that doesn't
go in the front and nothing comes out of a compost pile that didn't go into it
as far as the 16 or so essential plant nutrients are concerned.

Then we have Leibig's Law of the Minimum. This states that plant growth will be
limited by the least available nutrient and it further states that one nutrient
element cannot substitute for another. My soil here in Madera, for example,
has an a critical shortage of potassium but this will not be made up for by the
abundance of phosphorus. Plant and soil scientists believe that, in the end,
potassium will probably be the most critical element in maintaining soil
fertility.

Lastly there is the Law of Entropy which could be thought of as "the
disorganizing force" that always pulls on all that is organized. Each time the
elements of life, that is the 16 or 20 elements required for plant and animal
life, are assembled into plants, then reassembled into animals, then
remineralized back in the soil, there is a loss. In farms in gardens this
"leakage" takes place by leaching and erosion whereby the elements become widely
disbursed and unrecoverable. [Liquid fuels are made up of highly organized
molecules of carbon, hydrogen and oxygen but combustion "disorganizes" them
into carbon dioxide and water with the attendant loss of the sun's energy that
went into them.] As we know, it will take a very long time for them to get
reorganized back into petroleum based fuels.

In the end, agricultural sustainability will be limited by the rate at which
rocks can be weathered into soil and the minerals in those rocks made soluble.
This is why intensive beds alone cannot be relied upon to be sustainable
regardless of one's skill at making compost. A considerably larger area is
required to make the minerals in rocks available to plants and I suspect that
even 1 acre per person may not even be enough.

In discussing these ideas with Dr. James Farrar, Plant Science Department Head
at California State University, Fresno , he commented as follows. . .

"You are correct that composting will not add any minerals that are not present
in the animal or plant material. As you know, composting can change the nature
of the organic material and the population of microorganisms present in the
compost.

"The only mineral exception is that it is possible to incorporate nitrogen into
the system through the use of legumes. The downside is that that
legumes--Rhizobium symbiosis--is driven by low nitrogen availability so you
have to start with a nitrogen depleted soil in order to get much benefit. There
are also free-living nitrogen fixing bacteria that we are learning more about."

Please visit our website at . . .

http://www.wholesystemsag.org

for more good ideas about growing food in the difficult times. A global food
crisis may be at hand. with the USDA predicting only a 53 day supply for the
2007 crop year--half the supply of 1999 and the lowest ever since records have
been kept. Food production per person has been declining for years and the fact
that huge amounts of land are now being used for growing biofuels puts the Wolf
right near the door. Expect substantial food price increases soon if you
haven't noticed already.

In addition to honing up on gardening knowledge and skill I recommend laying up
a good supply of dry beans and peas. Read more in the Food Security section of
our website.

Good wishes and good growing, all

John Warner
Madera Whole Systems Agriculture near Fresno, California
No-tractor, no tillage market growers since 1996
http://www.wholesystemsag.org



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