Nitrogen in Manure

How can Nitrogen Affect Water Quality and Human Health?

Nitrogen is an essential nutrient for plant growth, and is one of the primary components of manure and commercial fertilizers. However, although nitrogen is very productive when applied to crops, excess nitrogen can have negative impacts in our lakes, rivers, and groundwater.
· Because of its fertilizing properties, nitrogen is a key contributing factor to algae growth in streams and lakes.
· Excess nitrogen in rivers and streams can be toxic to aquatic animals at high levels. This toxicity is due to ammonium hydroxide (NH4OH), which is produced at greater rates under conditions that are common where waste spills have occurred (such as low oxygen levels, high pH, and high temperature). Toxic levels of ammonium hydroxide are usually due to pollution from manure and sewage spills, and can result in fish kills and loss of other aquatic organisms.
· Nitrogen pollution also leads to human health concerns about groundwater contamination. Unlike phosphorus, which binds to the soil's surface, nitrogen filters down through the soil easily and can enter drinking wells. Infants less than six months are most susceptible to nitrate poisoning. High nitrate levels in groundwater can reduce the blood's capacity to carry oxygen, causing a fatal condition in infants called "blue baby syndrome." For this same reason, deaths can also occur in livestock that drink from a water supply high in nitrates. Pregnant or nursing women are advised to avoid water with high nitrate levels. Adults with heart or lung disease, certain inherited enzyme defects, or cancer may have increased sensitivity to the toxic effects, and adults with lifetime exposures to high nitrate levels may experience related health issues. The federal safety standard for nitrate is 10 mg/L, and 6.5% of Wisconsin's private wells exceed this safety standard.

How can Nitrogen and Phospherous Levels be Reduced?

For farmers, nutrient management is an integral part of business, and there are important steps that can be taken to reduce their nutrient loss to streams and lakes. The two main ways of reducing the nutrients that enter our waterways from agriculture are 1) decreasing the amount of nutrients applied to the landscape, and 2) preventing spills, runoff, and erosion from transporting those nutrients to our waterways. Decreasing excess nutrients applied to the landscape is the first step necessary for maintaining good water quality.
· Careful nutrient management planning can help farmers determine how much nitrogen and phosphorus is in their manure and how much the crops on each field require to be productive. This planning can help farmers apply only as much nitrogen and phosphorus as their crops will use, preventing excess runoff. In areas that already have phosphorus buildup in the soil or impacted waterways, farmers may need to manage specifically to reduce phosphorus levels.
· One way livestock operators can reduce unnecessary phosphorus in manure is by changing their feed supplements. Phosphorus is typically fed to cattle to ensure reproductive success. However, new research is showing that lower phosphorus levels in feed can be optimal for both maintaining herd health and for cost-effectiveness.

The second important step is to prevent the nutrients that are stored or applied to the land from getting into waterways.
· In many cases, manure should be stored over the winter while the ground is frozen. Because of this, manure storage facilities are a management option often chosen for operations that handle large quantities of manure. Sound construction and maintenance of these storage structures is essential to preventing leaks to groundwater and overflows that can damage nearby streams and lakes.
· Prevention of erosion and runoff is essential for keeping nutrients out of our lakes and streams. Maintaining good plant cover is one of the most effective ways to reduce the amount of soil and phosphorus that runs off into the water. Plant roots stabilize the soil and help reduce erosion. Buffer strips of grasses or trees along stream banks catch runoff and sediments flowing from upland fields and trap them before they enter waterways. Well-vegetated uplands and buffers are critical for water quality.

By following these practices and using good nutrient management planning, farmers can reduce nutrient-rich runoff from their farms and fields. This, combined with steps taken by all of Wisconsin's citizens and businesses, can help protect our beautiful water resources.


Source: http://www.dnr.state.wi.us/org/water/wm/nps/ag/waterquality.htm