to a crop farm will tend to lower the nutrient exports.
tend to be more readily lost to the environment. Even
In order to help balance nutrient imports and
midwestern U.S. cash grain farms that have balanced
exports, routine soil tests should become a part of every
nutrient imports and exports lose nutrients. Nitrogen-
farm’s practices, because they will indicate whether
leaching losses from these farms are having negative
nutrients are being depleted or accumulating to higher
environmental effects on the Mississippi River and Gulf
levels than needed.
of Mexico ecosystems.
SUMMARY
SOURcES
There is true nutrient cycling on most farms as crop
Anderson, B.H., and F.R. Magdoff. 2000. Dairy farm character-
istics and managed flows of phosphorus. American Journal of
residues or manures produced by animals fed crops
Alternative Agriculture 15: 19–25.
grown on the farm are returned to the soil. However,
Harrison, E., J. Bonhotal, and M. Schwarz. 2008. Using Manure
there are potentially large flows of nutrients onto and
Solids as Bedding. Report prepared by the Cornell Waste Man-
agement Institute (Ithaca, NY) for the New York State Energy
off of farms, and we are concerned about cases where
Research and Development Authority.
the flows are unbalanced. The inflow occurs as commer-
Magdoff, F., L. Lanyon, and W. Liebhardt. 1997. Nutrient cycling,
cial and organic fertilizers and amendments as well as
transformations, and flows: Implications for a more sustainable
agriculture. Advances in Agronomy 60: 1–73.
animal feeds are imported onto the farm and in manures
Magdoff, F., L. Lanyon, and W. Liebhardt. 1998. Sustainable
and composts brought from off the farm. Exports are
Nutrient Management: A Role for Everyone. Burlington, VT:
mainly in the form of crops and animal products. In
Northeast Region Sustainable Agriculture Research and Educa-
tion Program.
general, larger amounts of nutrients are exported off the
Morris, T.F. 2004. Survey of the nutrient status of organic veg-
farm in vegetation (grains, forages, vegetables, etc.) than
etable farms. Search for project report LNE01-144 in the SARE
in animal products. This happens because a high percent
project database, http://www.sare.org/projects.
of the nutrients in the feeds pass through the animal and
Rasmussen, C.N., Q.M. Ketterings, G. Albrecht, L. Chase, and K.J.
Czymmek. 2006. Mass nutrient balances: A management tool
are available as manure. And relatively few nutrients
for New York dairy and livestock farms. In Silage for Dairy
are exported per acre in the form of milk, meat, wool,
Farms: Growing, Harvesting, Storing, and Feeding, pp.
396–414. NRAES Conference, Harrisburg, PA, January 23–25.
etc., compared to the amount exported from crop farms.
Seiter, S., and W.R. Horwath. 2004. Strategies for managing soil
Nutrient flows are of such great concern because as
organic matter to supply plant nutrients. In Soil Organic Matter
nutrient levels decline, the soil rapidly degrades. On the
in Sustainable Agriculture, ed. F. Magdoff and R.R. Weil, pp.
269–293. Boca Raton, FL: CRC Press.
other hand, when nutrients build up on the farm, they
74
Building SoilS for Better CropS: SuStainaBle Soil ManageMent
