Agriculture Reference
In-Depth Information
often just multiply the amount of nitrogen the crop needs by
two. For phosphorus around 30 percent of the amount applied
isn't consumed by the crop.
It is becoming evident that farmers can apply less fertil-
izer with little sacrifice in yield, especially in some developing
countries. Farmers apply excessive fertilizer for a number of
reasons. In China it has to do with memories of famines in the
Mao era, in India it is related to the large fertilizer subsidies,
and in Japan it is partly because so many rice producers are
only part-time farmers who do not have time to perfect their
management skills.
One obvious solution is to remove fertilizer subsidies where
they exist and perhaps even tax fertilizers, but this is dif-
ficult in poorer countries with food security issues. A tax is
more feasible in richer countries. In 2013 the California Water
Resources Control Board actually recommended placing fees
on fertilizer use, in order to help offset the cost of treating
drinking water polluted with excess nitrogen. A 1992 fertilizer
tax in Sweden reduced use by 15-20 percent, and if farmers
were indeed applying too much before the tax, the sacrifice in
yield may have been minimal. With the support of both farm-
ers and environmentalists, the state of Illinois instituted a fer-
tilizer tax not to discourage its use, but to fund research on its
environmental impact and ways to reduce runoff.
New technologies in precision agriculture can vary the fer-
tilizer application rate across a field, probably reducing excess
fertilizer in the process. Called “filter strips,” a buffer of unfer-
tilized permanent grass can be placed between the crop and
the edge of a field to catch fertilizer runoff. Studies have shown
that filter strips can eliminate over half of all fertilizer run-
off, as well as reduce soil erosion. However, they can be costly
because they reduce the amount of land in crops and require
maintenance, so they are sometimes subsidized by agencies
like the USDA or individual states like Iowa. Minnesota has a
ban on crops within fifty feet of a stream to ensure a vegetative
buffer between the crop and surface waters. Through a variety
