Water Quality Challenges

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.

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.

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.

Animal manures contain both organic and inorganic forms of phosphorus. When manure mineralizes, organic phosphorus becomes inorganic phosphorus in solution and is available to plants. Some organic phosphorus is transformed to inorganic form shortly after application but other phosphorus will remain in organic form

When designed properly, runoff holding ponds, lagoons, and other earthen manure storage structures are sized to contain manure, process wastewater, and storm water that drain into or fall on them throughout their designed storage period. Excess precipitation, particularly chronic wet weather, can lead to concerns about storages overflowing even when they have been managed correctly.

Spring manure applications may provide environmental and crop production advantages compared to fall manure applications. These benefits include reduced nitrogen leaching, increased crop yields, and higher phosphorus and potassium nutrient soil storage.

Iowa State University researchers concluded from a long-term field study that poultry manure, when applied at a rate to meet the crop nitrogen (N) requirements, can reduce nitrate loss and achieve equal or better yields in corn soybean production systems. While this research focused on nitrate (NO­3-N) loss by field-tile drains (typically placed 3 to 6 feet deep), similar trends would be anticipated in Nebraska for nitrate leaching below the crop root zone and the eventual impacts on surface and ground water quality.

Algal blooms may occur in bodies of water with excess amounts of nitrogen and phosphorus. These algal blooms are detrimental to fish populations, other animal populations, and possibly human health.