Agriculture Reference
In-Depth Information
23
Manning, Richard,
Grassland
, Penguin, p 179.
24
Spainhower, Richard,
Cheatin' Heart
, BASF Advertorial, The Dickinson Press, Dickinson, N Dakota 2003,
ht-
25
Manning,
op cit
. 23, p 127.
26
Young, James A and Clements, Charlie D 'Cheatgrass' (2007), USDA Agricultural Research Centre Reno;
University of Idaho (2006),
Cheatgrass or Downy Brome, Targeted Grazing
,
http://www.cnr.uidaho.edu/rx-grazing/
27
Holechek, Jerry, 'Short Duration Grazing: The Facts in 1999',
Rangelands
22(1), 2000,
http://uvalde.tamu.edu/
28
Described as 'weak' by another correspondent to the magazine. I have so far been unable to obtain a copy of
Savory's reply. In November 2009 I attended a talk by Savory in London, and asked him what his response was to
Holechek's criticism. He referred me to an article on his website entitled 'Doing the Right Thing'. However this article
answers none of Holechek's criticisms, and the name Holechek doesn't give any results on the site's search facility. Rio
de la Vista (2001),
Doing the Right Thing - The McNeil Ranch
, Holistic Management in Practice, July/August 2001.
ht-
29
D. D. Briske et al, (2008), 'Rotational Grazing on Rangelands: Reconciliation of Perception and Experimental
Evidence', Rangeland Ecol Manage 61:3-17 | January 2008.
http://essm.tamu.edu/people/briske/documents/REMSyn-
30
Pollan, Michael (2006),
Omnivore's Dilemma
, Bloomsbury, p 192.
31
Dagget (2005),
op cit. 22
, pp 128-9.
32
Yeomans, Allan J A (2007),
Priority One
, Biosphere Media,
http://www.yeomansplow.com.au/priority-one.htm
.
Yeomans arrives at his 1.6 per cent through the clumsy device of imagining columns of atmosphere and layers of soot,
and does so on the grounds that 'quoting huge numbers with lots of noughts is confusing and usually becomes meaning-
less, that's why it's fed to us.' Actually it's his layers of soot that are confusing - like those football fields in the rain-
forest. Fortunately, Peter Donovan of the Canadian group, the Soil Carbon Coalition, has taken the trouble to transcribe
Yeoman's figures clearly into conventional mathematical units that can be compared easily with everybody else's. His
calculations are as follows: The atmosphere currently contains about 800 Gt (gigatons or billion metric tons) of carbon.
The vast majority of this is in the form of carbon dioxide, which is currently about 383 parts per million (Yeomans used
380 ppm for his calculation). Each of these parts per million = 800/383 = 2.089 Gt C. So, to take out 80 ppm we are talk-
ing about removing 80 x 2.089 or 167 Gt (167,000,000,000 metric tons) of carbon from the atmosphere. Soil density is
usually between 1.2 and 1.4 on a dry basis. That is in relation to the density of water which is 1.0. A hectare of soil (100 m
x 100 m), 12 inches or 30.48 cm deep, has a volume of 3,048 cubic metres. At a soil density of 1.2, this foot-deep hectare
of soil weighs 3,658 metric tons. One per cent of this weighs 36.58 metric tons, and if this 1 per cent is organic matter
(58 per cent carbon by weight), it contains 21.21 tons of carbon. According to the World Resources Institute (
World Re-
sources 2005: The Wealth of the Poor-Managing Ecosystems to Fight Poverty
, table 11, p 216), there are 5,096,000,000
hectares of crop and grazing land worldwide. Dividing the 167 billion tons we aim to remove by this figure, each hectare
has to take, on average, 32.8 tons of carbon. Since each per cent of organic matter in the top foot of soil contains 21.21
tons of carbon, this comes to roughly 1.56% as the amount of soil that we must convert to organic matter on the top foot
of these lands, to lower atmospheric concentrations by 80 ppm. In other words, if the organic matter content is currently
