-----Original Message-----
From: Laurel Hopwood <
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To: CONS-SPST-BIOTECH-FORUM <
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Sent: Fri, Dec 25, 2015 9:05 am
Subject: Organic farming can cut nitrate leaching in half
http://www.desmoinesregister.com/story/opinion/abetteriowa/2015/12/24/organic-farming-can-cut-nitrate-leaching-half/77774262/
Organic farming can cut nitrate leaching in half
by soil scientist and organic farmer Francis Thicke (and others). Email:
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(edited)
Recent research published by Cynthia Cambardella and Dan Jaynes, USDA
Agricultural Research Service in Ames and Kathleen Delate, Iowa State
University in the journal “Sustainable Agriculture Research”
demonstrated that a typical organic crop rotation reduced nitrate
leaching from crop fields by nearly 50 percent, compared to the
conventional corn and soybean rotation common in Iowa.
The researchers measured how much nitrate leached down through the soil
profile and out through the field tile drainage systems, which drain
into streams and rivers. Over three years, the conventional corn/soybean
cropping system leached a total of 69.7 lb/acre of nitrate-nitrogen,
compared to 35.1 lb/acre for the organic cropping system.
Certified organic production requires more diverse cropping systems. As
in this field experiment, small grain crops (like oats, wheat and rye)
and perennial crops (like alfalfa and forage grasses) are normally
included in organic crop rotations. Perennial and small grain crops can
be efficient scavengers of soil nitrate. Perennial crops have live roots
in the ground all year long, compared to annual crops which have live
roots in the ground for approximately five months of the year. Perennial
crops provide uptake and recycling of nitrate and protection against
nitrate leaching during times of the year when annual crops cannot.
Second, in conventional agriculture, nitrogen is supplied to crops in
synthetic, mineral forms. Those forms become rapidly available for crop
uptake, but are highly water soluble and susceptible to leaching when
rainfall percolates through the soil profile. In organic farming
systems, nitrogen is supplied to crops in organic forms — such as legume
crops, compost or manure — which are incorporated into the soil. Organic
forms of nitrogen are not immediately available for crop uptake or for
leaching, but are released slowly throughout the growing season into
mineral (plant-available) forms by soil microbes, matching the timing of
crop needs for nitrogen during the growing season, thereby reducing the
potential for nitrate leaching.
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