![Photo: Dairy cows feeding. Link to photo information](https://webarchive.library.unt.edu/web/20090509202413im_/http://www.ars.usda.gov/is/graphics/photos/feb98/k7964-1i.jpg) Manure from dairy cows fed
organic diets contained different concentrations of plant nutrients, including
phosphorus, metals and minerals compared to manure from cows fed conventional
diets. Click the image for more information about it. |
![For further reading](https://webarchive.library.unt.edu/web/20090509202413im_/http://www.ars.usda.gov/is/graphics/For-further-reading.gif)
|
Organic Dairy Manure May Offer Fertilizer
Option
By Ann
Perry April 22, 2009
Dairy cows that produce USDA-certified organic milk also produce
manure that may gradually replenish soil nutrients and potentially reduce the
flow of agricultural pollutants to nearby water sources, according to findings
by Agricultural Research Service (ARS)
scientists and colleagues.
Cows on organic dairy farms generally consume forage feeds cultivated
on soils that are fertilized with manure and compost rather than manufactured
fertilizers. This organic management, in turn, may significantly affect how
easily nutrients are converted in soil into forms readily taken up by crops.
Working with colleagues at the ARS
New
England Plant, Soil, and Water Laboratory in Orono, Maine, and elsewhere,
chemist
Zhongqi
He showed that conventional and organic dairy manures from commercial dairy
farms differed in concentrations of plant nutrients, including phosphorus,
metals and minerals.
The team used two different types of nuclear magnetic resonance (NMR)
to pinpoint these differences. Solution NMR spectroscopy is already widely used
to analyze phosphorus content in manure. For this study, the scientists also
analyzed manure content using solid-state NMR spectroscopy, which is especially
effective at finding unique signatures of the different kinds of
metals and minerals.
The researchers found that the two types of manure had at least 17
different chemical forms of phosphorus that varied in concentrations. The
organic dairy manure had higher levels of phosphorus, calcium, potassium,
manganese, zinc and magnesium.
Organic dairy manure also contained more types of phosphorus found in
association with calcium and magnesium. Such forms are comparatively slow to
dissolve and would thus gradually release the nutrients. Slow-release
fertilizers generally increase the likelihood that they eventually will be
taken up by crops, rather than being washed out of fields into nearby surface
or groundwater sources.
Because of this, slow-release fertilizers often can be applied at
comparatively low rates. Manure produced by cows in organic production systems
may show similar characteristics compared to manure from conventional systems.
ARS is the principal intramural scientific research agency of the
U.S. Department of Agriculture.