Agriculture Reference
In-Depth Information
US rivers and estuaries are 44 percent and 30 percent, respec-
tively. More than half of lakes in China suffer from too much
fertilizer. Groundwater can be contaminated by excess nitro-
gen also, and can cause blue baby syndrome and other health
problems. Even Austrian springs considered by the Catholic
Church to be holy water are contaminated with enough nitro-
gen to cause illness. The damage to waters are thus caused
by the success of modern agriculture. The challenge now is
to restore these waters while maintaining an adequate food
s upply.
Not all the fertilizer applied to a field will be consumed by
the plant. Some will leave the field as surface runoff or subsur-
face leaching. Though that excess fertilizer will not feed the
crop, it will feed something. It may fertilize plants growing on
the side of a field, trees downhill from the field, or bacteria and
algae in rivers. If enough fertilizer reaches surface waters, it may
cause explosions in bacteria and algae populations, and as the
populations expand they consume more oxygen from the water.
Eventually the water might reach eutrophication, where oxygen
is so scarce that no aquatic life can exist. The water becomes
cloudy, and using the water for drinking may require expensive
treatment. In the Gulf of Mexico there is a “dead zone” of about
3,100 square miles, so this is no minor problem.
Restoring water quality first requires us to understand all
the sources of eutrophication, since chemical fertilizers are not
the only one. Livestock manure is responsible for most of the
pollution in the Chesapeake Bay and the Illinois River. In other
areas lawn fertilizers cause the most damage. Phosphorus in
dishwashing detergents was a major pollutant in the US Great
Lakes, which is why most detergents now say, “Contains no
phosphorus.”
It is simply hard to apply fertilizer of any kind and not
experience some runoff. Roughly half of all applied nitrogen
fertilizer will not be consumed by the crop, which means it
fertilizes other plants or enters waters. When agronomists
make recommendations on how much nitrogen to apply, they
