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  • From: "John D'hondt" <dhondt@eircom.net>
  • To: "permaculture" <permaculture@lists.ibiblio.org>
  • Subject: Re: [permaculture] [soilandhealth] Organic matter percentage
  • Date: Wed, 28 Dec 2011 19:00:46 -0000


I agree that razing can improve the land but...what this really amounts to usually is rearing animals on grass and then selling them of the land and by doing this you export a serious amount of nutrients.
We could see the result of that sort of practice when we first started farming in Ireland on land that had exported foodcrops for hundreds of years and had almost no soil left, just subsoil and bare rock. We had no option but to import organic matter and in the beginning it was obvious that even then we were loosing the battle for improving our soil by selling lambs and beef. We finally began to see a difference when we could get our hands on tons and tons of free fish waste. This mixed with a carbon source made a difference fast.
On the Midwestern Prairies grazers died or were eaten on the spot by predators and so left the nutrients captured in their bodies in place. Also all kinds of birds especially tend to spread out the goodies over large distances. Not much use to us in Ireland where we are one of the few farms left with food for wild birds in the middle of green desert. Once again nutrients are leaving our farm because of this.
john

From a practical standpoint, 50,000 lbs of organic matter is a _lot_ of
material. That is 50 loads on a half ton pick-up truck, or about a load
a week per acre (208' x 208'). That would require the application of
1250 40 pound bales of straw per acre, for example. Since I only bring
chemical free organic matter onto my ecofarm, I have not found sources
for that much mass, and I really don't want to. Of my 63 acres, 20 are
tillable (the rest is hardwood forest), so I would need to bring in one
million pounds of matter to raise SOM by 1%. The most practical way to
increase SOM of any significance in temperate climates is by grazing
animals on grass. That is how and why the Midwestern tall grass prairie
(Eastern corn belt) and the central plains attained SOM levels of 8-10
percent. Louis Bromfield claimed he was generating 1" of topsoil per
year on Malabar Farm in Ohio, USA.
http://www.youtube.com/watch?v=AEBoAEb7Opw

Steve
Indiana USA


On Mon, Dec 26, 2011 at 11:12 PM, Toby Hemenway
<toby@patternliteracy.com>wrote:
Although 50,000 lbs sounds like a lot, it's only about 20 cubic yards per
acre, 40 at most. So it's not that hard to boost SOM using compost (even
though I'm a big fan of mulches).

Toby
http://patternliteracy.com

On Dec 26, 2011, at 3:13 PM, Glenn Gall wrote:

On 9/18/2011 2:03 AM, m_astera wrote:
How much compost or manure would one need to add to raise the Soil
Organic Matter SOM content of an acre of soil 6" deep by 1%?

SOM percentage is calculated by weight, not volume. The convention
used is that 1 acre of soil 6-7" deep weighs 2,000,000 (two million)
pounds. Or a hectare of soil 15cm deep weighs 2,000,000 kg. One
percent of that is 20,000 lbs/acre or 20,000 kg/ha
Compost and manure can be assumed to be around 60% moisture and 40%
dry organic matter. So

20,000 / 0.40 = 50,000

To add 1% organic matter to the top 6" or 15cm of soil would require
about 50,000 lbs/acre or 50,000 kg/ha of organic matter at 60%
moisture content.
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