Fertilizers and their Impact on Watershed Ecology

Nitrogen and phosphorus pollution ranks as one of the top causes of degradation in some U.S. waters for more than a decade. Large amounts of nitrogen and phosphorus lead to regional water quality problems like algal blooms, hypoxia and declines in wildlife habitat.

“Aerobic conditions” in water ways signifies the presence of oxygen in a hydrological system.  The natural cycles of the water feature may be more or less in balance until an excess of nitrate, or nitrogen, and/or phosphate enters the system. At this time, water plants and algae begin to grow more rapidly than normal. There is also an excess die off of plants and algae as sunlight is blocked at lower levels. Bacteria try to decompose the organic waste, consuming the oxygen, which reduces fish populations, and releases more phosphate which is known as “recycling or internal cycling”. Some of the phosphate may be precipitated as iron phosphate and stored in the sediment where it can then be released if anoxic conditions develop.

Fertilizer Effects on the Water Shed

Industrial agriculture is a leading cause of water pollution in the U.S. In the 2000 National Water Quality Inventory conducted by the Environmental Protection Agency (EPA), agricultural activity was identified as a source of pollution for 48% of stream and river water and for 41% of lake water.  Many small sustainable farms conserve water and apply waste and fertilizer to fields responsibly, minimizing their impact on local water systems.

Dead zones have already begun to appear, notably in the Gulf of Mexico,
which is fed by nitrogen-rich water from the Mississippi river. "We are
looking at major effects in the US, Europe and south-east Asia," Dr Watson

As the world's population is estimated to grow to 9 billion in 40 years,
food production is expected to become more intensive, requiring ever more
nitrogen-rich fertiliser.

Kenneth Cassman, an expert on environmental health at the Universityof
Nebraska, said the efficiency of nitrogen use needed to be "massively
improved". "There are a number among us who think this is more important
than carbon emissions, in terms of environmental impact," he said.

In a separate part of the study, the scientists found that global warming
would severely disrupt ecosystems, especially in the developing world, if it
was not kept in check. An increase of more than 2C (3.6F) would be enough to
severely degrade the availability of food, water and human health in
developing countries.

"We can move in a direction where we destroy our natural heritage or we can
move in a direction where we improve both human wellbeing and maintain our
natural heritage," he said. "We've got choices and we have to decide which
future we want."