Re: Sediment Reduction with Organic Farming

E. Ann Clark, Associate Professor (ACLARK@CROP.UOGUELPH.CA)
Sat, 6 May 1995 00:10:56 EDT

The first answer to this question relates to the fundamental
philosophy of organic farmers toward internalizing nutrient and
energy cycling on the farm. Much has been written on this, but at
the heart of it is an unwillingness to allow erosion to occur - not
because it will affect profit margin or incur the wrath of
downstream neighbors, but because it means lost nutrients and/or
9organic matter (energy). Recall that what is lost in erosion is the
uppermost, most OM-rich soil - the stuff that "feeds" the nutrient
and energy cycles leading to humus. Because organic farmers are
contrained (esp if certified) in what can be imported to the farm,
they make extraordinary efforts to avoid nutrient loss. I know of
two farmers - an organic dairy and a conventional beef - who have
absorbed the cost of building a roof over their manure storage pads,
just to avoid losing nutrients by leaching. The former uses this pad
to "pre-compost" his manure before laying it out in windrows outside.
Liquid fractions are directed down a concrete pad into a drain, from
which they are cycled into a liquid manure storage tank for later
application to cropland.

The second answer relates to "how" organic farmers approach the
philosophical and practical requirements of nutrient and energy
cycling. One obvious means is by crop choice. For example, organic
livestock farmers (in Ontario at least) rely heavily on small grains
(7" rows, rapid attainment of full cover, potential for winter- as
well as spring/summer-groundcover) for their carbohydrate
requirements. There is ample evidence in the literature on the much
greater potential for erosion under wide-row crops, such as corn, as
compared to narrow row cereal crops. Another means of avoiding
erosion is by sustaining groundcover for as many months of the year
as possible. Organic farmers routinely strive for winter cover,
whether as a winter cereal or a plowdown red clover crop or a
winter-dead catch crop such as oilseed radish.

Both of these issues could be quantitated by doing or finding
existing surveys on organic farming methods in your area to create a
composite picture of crop type (% of land under various crops, for
each system), then digging out the ample conventional lit on erosion
with crop type and winter cover to create an aggregate index of
potential soil erosion under organic vs. conventional approaches to
agriculture. Good luck. Ann

ACLARK@crop.uoguelph.ca
Dr. E. Ann Clark
Associate Professor
Crop Science
University of Guelph
Guelph, ON N1G 2W1
Phone: 519-824-4120 Ext. 2508
FAX: 519 763-8933