Water Quality Challenges

Nitrogen Dynamics

Nutrients in manure are potentially valuable resources for the management of soil fertility, but these nutrients are potential pollutants as well. Only 10 to 40 percent of the nutrients consumed by animals may end up in the marketed product; the rest is excreted in feces and urine. Manure contains all nutrients needed by plants, but nitrogen and phosphate generally have the most agronomic significance in Nebraska.

Understanding Water Quality Issues

Manure contains four primary contaminants that impact water quality: nitrogen, phosphorus, bacteria and other pathogens, and organic matter.

Manure Nutrient Losses

Manure nutrients are lost during manure handling, storage, treatment, and application. Manure nitrogen is especially vulnerable to volatilization when ammonium is transformed to ammonia. Losses of phosphorus and potassium are primarily due to runoff and erosion.

Pathogens and Organic Matter

Pathogens, typically microbes (e.g., bacteria, viruses, protozoa, fungi) or parasitic worms, are organisms capable of causing infection or disease in other organisms, including humans, wild and domestic animals, and plants. Several pathogens naturally occur in livestock and poultry manure and under certain circumstances may pose a risk to human health.

Phosphorus Loss

Land application of manure can be beneficial to crop production but can result in increased risk of P loss to surface waters. When manure is applied to meet crop nitrogen needs, the amount of P applied is typically much more than the P removed in the harvest of one crop. Effective January 1, 2007, operators of large CAFOs in Nebraska need to assess the risk of P delivery to surface waters from each of their designated fields by using a P index before manure can be applied.

Contaminant Pathways

Water quality can be degraded by contaminants contained in manure, from water used at milking centers, from silage leachate, and from open lot runoff. These potential pollutants typically follow one or more possible pathways to water.