We need to
understand that the farmer applies fertilizer so that the plant
would take it up and use it for growth. The fact that some of the
fertilizer is polluting water means that it is not being taken up by
the plant. In addition to being an environmental problem, it also a
waste of money for the farmer. The solution is to get the plant to
use the fertilizer that is applied.
The key is to ensure
that we have a good growing conditions so that the crop can take up
and make use of the applied nutrients. It means that we must have a
productive crop variety suited to that area, planting must be
properly done, pests, weeds and diseases must be controlled, in
fact, all operations must be done properly. One important aspect of
proper conditions is balanced nutrition. There must be an adequate
supply of all of the other nutrients if the crop is to make use of
the applied nitrogen and phosphorus.
With nitrogen, it is
critical to apply no more than is needed; any excess is certain to
contribute to some form of pollution. Soil testing has not been
sufficiently reliable to predict nitrogen needs, therefore the crop
requirements determined by local testing are also used.
application of nitrogen is also important. Because it does not
remain in the soil for very long, it is usually better to apply
small, regular doses. It is best to time the applications to
coincide with the periods when the crop needs it the most. This is
where fertilizers have a big advantage over manure. It is not
possible to control the release of nitrogen from manure. It may
occur at a time when the crop does not need nitrogen allowing it to
be easily leached out of the soil.
There are a few
chemicals which can modify the rate at which nitrogen reacts in the
soil and reduce the chance of pollution. Urease inhibitors work by
slowing down the rate at which urea is converted into ammonium
nitrogen. Nitrification inhibitors reduce the rate at which ammonium
nitrogen is converted into nitrates. The idea is to try to produce
nitrate in the soil at the same rate at which the crop is using it
so that there will be no excess that can be leached.
fertilizers use physical coatings on the fertilizer granules to
control the release of nutrients. Again, the idea is to match the
release of nutrients with the rate of uptake by the crop.
measures can dramatically reduce phosphorus pollution. Again,
balanced nutrition is a key element in that it promotes the rapid
growth of plants whose leaves and residue protect the soil from
direct rainfall. Reduced tillage and physical conservation measures
have done a lot to protect surface water from the effects of
phosphates transported with eroded soil.