Academic journal article Journal of Agricultural and Applied Economics

Phosphorus-Based Applications of Livestock Manure and the Law of Unintended Consequences

Academic journal article Journal of Agricultural and Applied Economics

Phosphorus-Based Applications of Livestock Manure and the Law of Unintended Consequences

Article excerpt

The application of manure phosphorus at rates above crop uptake has resulted in water pollution for some regions. In response, new manure management standards will require some farms to match manure phosphorus application rates with crop uptake. For some regions, this will lead to more crop acres and a shift toward crops with greater nutrient uptake, both of which will increase nitrogen runoff. The greater nitrogen runoff could offset the lower phosphorus runoff to result in greater water pollution. This demonstrates the law of unintended consequences, which results when policy does not consider how economic agents respond to incentives.

Key Words: best management practice, eutrophication, manure management, nutrient run-off, phosphorus standards, pollution control, water pollution

JEL Classifications: D6, Q1, Q2

During the 180Os, the predominant sources of fertilizer were human manure, livestock manure, and Chilean guano. Technological advancements have since yielded more efficient means of fertilizing crops. After we learned to create superphosphate by applying sulfuric acid to phosphate rock, phosphorus could be mined cheaper than it could be obtained through manure. Perhaps the greatest breakthrough was the discovery of ammonia synthesis, in which nitrogen could be extracted directly from the atmosphere. Because of these breakthroughs, chemical fertilizer use has risen from almost nothing to 40 million tons in 1965 and 150 million tons in 1990 (McNeil). In fact, chemical fertilizer prices are now so low that many livestock farms find it more expensive to apply manure to fields adjacent to where the manure is generated than to fertilize those fields with chemical fertilizers. Because of chemical fertilizer prices, farmers think of livestock manure less as a fertilizer and more as a burden.

Because of large manure transportation costs, production costs on many farms can be reduced by overapplying manure close to where the manure is generated. Overapplications of manure mean that some manure nutrients go unused by the crop. This has resulted in water quality problems in some areas. Excess nutrients (nutrients applied but not harvested) have the potential to leave the field and enter surface waters, where they encourage algae and bacterial growth. As the populations of these microorganisms rise, they can eventually consume all of the water's dissolved oxygen, causing the aquatic ecosystem to collapse in what is referred to as eutrophication. Even before eutrophication occurs, the algae can produce a toxin that makes the water undrinkable without expensive treatment.

The microorganisms causing eutrophication, like all life forms, require both nitrogen and phosphorus for growth. If waters contain plentiful phosphorus but little nitrogen, nitrogen is said to be the limiting nutrient. This means that additional nitrogen will cause more pollution, but additional phosphorus will not. For some waters, nitrogen is the limiting nutrient and water pollution policies only manage nitrogen. In the North Carolina Neuse River Basin, proposed regulations would require each county to reduce their nitrogen loads to surface waters by choosing among various best management practices, such as conservation tillage, controlled drainage, and filter strips (Schwabe 1996, 2001). Phosphorus loadings to the basin, however, would not be regulated.

In other waters, phosphorus is the limiting nutrient. In the 1960s, Lake Erie was deemed a dead lake. This led to a series of studies that concluded that Lake Erie and 10,000 other U.S. lakes suffered from high phosphorus loadings. Regulations banning phosphatebased detergents and upgrading waste treatment plants later restored some health to these waters (U.S. Geological Survey 1999).

As another example, the Eucha-Spavinaw watershed, shared by Oklahoma and Arkansas, has received massive loads of phosphorus from the overapplication of poultry litter, making the water undrinkable. …

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