Nitrogen Pollution from Animal Waste,
December 2006 Bay Journal

A Virginia Joint Legislative Audit and Review Commission (JLARC) recently released report No. 89, “Review of Land Application of Biosolids in Virginia” which was rightly critical of the management of the land-application of municipal sewage sludge (“biosolids”) by the Virginia Department of Health (VDH). An Inspector General’s Report (2002-S-000004) and a report from the National Academy of Sciences (7-2-02) were similarly critical of EPA’s out-of-date and inadequate management and enforcement policies regarding sewage sludge. The reports concentrate on human health issues and ignore the environmental consequences of nitrogen and phosphorus pollution caused by the land-application of sewage sludge. Nobody questions the potential benefits of land-applying animal waste (poultry litter, manure and sewage sludge) to supply nitrogen, phosphorus and other nutrients, to increase soil quality and to reduce the cost of chemical fertilizer. But the cost to society of the pollution resulting from using such a very inefficient form of fertilizer must also be clearly understood.

The Chesapeake Executive Council, EPA and even the Chesapeake Bay Foundation have not addressed this issue seriously, always siding with agricultural interests. Chesapeake Executive Council Directive 04-3 (2004) proposes six “…solutions for reducing nutrient pollution from animal manure and poultry litter.” None of the “solutions” are mandated and some are meaningless, not unlike the “promises” in a previous Chesapeake Executive Council Directive (98-04 in 1998) that have not reduced nitrogen or phosphorus pollution after eight years. In “Assessing the State of Chesapeake Bay Agriculture, 2005” CBF claimed that “…farmers are managing commercial fertilizer more efficiently and substituting manure for commercial fertilizers, a smart move if manure is applied based on careful soil testing.” Based on what is presented below, referring only to practices in Virginia, the reader can judge whether or not using animal waste as fertilizer is a “smart move” if the goal is to improve water quality in Chesapeake Bay. A more thorough discussion and links are posted at www.VaBayBlues.org.

The JLARC report states that 232,000 dry tons of sewage sludge were spread on roughly 50,000 acres in Virginia in 2004, resulting on cost savings for farmers of about $56 per acre. This tonnage of sewage sludge, more than half of it from out-of-state, is similar to the tonnage supplied to me by the VDH and the Department of Environmental Quality for 2003. The Department of Conservation and Recreation (DCR) quantified the tons of poultry waste and manure land-applied in 2003. Here are the pounds of the three forms of animal waste (dry weight) land-applied in Virginia in 2003 according to the three state agencies. The fractions of the nitrogen in the animal waste and the fractions of the nitrogen not used by crops are from DCR’s “2005 Nutrient Management Standards,” Tables 8-2, 8-3, 8-4 and 9-1, on which Nutrient Management Plans are based. It is presumed that Nutrient Management Plans are being followed, which is certainly true for sewage sludge, but is not true for all the poultry litter derived from out-of-state, either because Nutrient Management Plans are not required or because they are not being enforced.

Pounds applied * fraction N * fraction N not used = pounds N pollution

Sewage sludge 494,648,000 * 0.02 * 0.45 = 4,452,000

Poultry litter 1,115,268,000 * 0.03 * 0.30 = 10,037,000

Other manure 468,509,000 * 0.03 * 0.50 = 7,028,000

21,517,000

Approximately 22 million pounds of nitrogen was land applied beyond what was needed to support the growth of crops in 2003, even if Nutrient Management Plans were followed. For perspective, 22 million pounds is similar in magnitude to the 26 million pounds released annually by wastewater treatment plants in Virginia. Not all of the excess nitrogen from biosolids and animal manure reaches waterways. But a significant amount of the excess nitrogen will eventually find its way into local streams, and eventually the Chesapeake Bay.

EPA is now claiming, to nobody’s surprise, that the touted nutrient reduction goals for Chesapeake Bay will not be achieved by 2010. That is because neither EPA nor the states have mandated that wastewater treatment plants be modernized immediately to reduce nutrient release, but more important, because voluntary agricultural fertilization efficiency has not improved significantly watershed-wide. Irrespective of claims that “…farmers are managing commercial fertilizer more efficiently …” the Bay acreage covered by submerged aquatic vegetation has not increased significantly and the volume of Bay water in the summer “dead zones” has not decreased. Water quality is not improving. It has been known for one-third century, since the EPA’s original Chesapeake Bay study in 1983, that agricultural practices are the largest source of nitrogen and phosphorus pollution of Chesapeake Bay. The land-application of animal waste is the most egregious and easily addressed source of agricultural pollution.

Even conventional fertilization using chemicals rather than animal wastes causes a great deal of pollution. Worldwide, the Nitrogen Use Efficiency of cereal crops is estimated at approximately 42 percent according to a well-referenced article in the 1999 Agronomy Journal (Volume 91, pages 357-363). In Northumberland County, the NUE is better. The average yield for corn is 130 bushels of grain per acre and 130 pounds of chemical nitrogen fertilizer (usually ammonium nitrate) is typically applied per acre to grow the crop. A bushel of corn weighs 64 pounds and contains about 15 percent moisture and 1.5 percent nitrogen on a dry-weight basis. This means that about 106 pounds (130 * 64 * 0.85 * 0.015) of nitrogen is removed from each acre of the field with the grain so that the Nitrogen Use Efficiency in Northumberland County is about 82 percent (106 / 130.) What happens to the other 24 pounds (130 – 106) of N? Some is converted to nitrogen gas, and some is intercepted by wetlands and riparian buffers, but a significant portion ends up in local streams. The bottom lines is that even chemical fertilization, under the best of circumstances, is “leaky” and typical single-application rarely releases less than about 1/4 of the applied nitrogen to the environment

When animal waste (poultry litter, manure or municipal sewage sludge) is used as fertilizer, pollution is greatly increased because about half the nitrogen is not “crop available.” Approximately twice as much nitrogen is land-applied using animal waste as would be applied using conventional chemical fertilizer, to grow exactly the same crop.

I observed the land-application of sewage sludge in Northumberland County in March of 2004. Based on the submitted Nutrient Management Plan, 24,770 pounds of nitrogen were spread on 72.4 acres in accordance with Table 9-1 in DCR’s “Nutrient Management Standards.” If chemical fertilizer had been used, 7,431 pounds of nitrogen would have been applied. Lime-stabilized sewage sludge is applied on the basis that 30 percent of the nitrogen is crop-available the first year, 10 percent the second and third years, and 5 percent the fourth year. Fifty-five percent of the nitrogen is presumed to be crop-available over four years. The nitrogen application rate is determined by dividing the chemical fertilization rate by 0.3, or the amount of nitrogen available to the crop the first year (24,770 = 7431 / 0.3). This specific application to 72.4 acres caused at least 11,000 pounds of nitrogen (more than 2000 50 pound bags of 10-10-10) to be applied with no benefit for the crop.

Farmers know that roughly twice as much nitrogen is applied using animal waste as would be applied using chemical fertilizer, to grow exactly the same crop. As long as the land-application practice is sanctioned, or even promoted, how can we expect farmers to voluntarily apply Best Management Practices (BMPs) such a split fertilizer application and unfertilized winter cover crops, which reduce their profits, and which increase Nitrogen Use Efficiency less than the inefficiency involved in the use of free or inexpensive animal waste? The specific fate of the excess nitrogen applied when animal waste is used as fertilizer (denitrification, ammonia volatilization, NOx release, etc.) as a function of soil type, rainfall, etc., and the amount of the nitrogen consumed by riparian buffers can be studied forever, and although interesting scientifically, scientific uncertainty is not a reason for inaction. There is no getting around the simple fact that conventional chemical agricultural fertilization is far from 100 percent efficient, and can be improved significantly. If the amount of nitrogen applied to the land is doubled to grow the same crop by using animal waste, the pollution is increased.

Everyone must recognize that the cost savings involved in the land-application of animal waste for poultry-growers (and poultry-purchasers), a few farmers, and the profits of the land-application industry come at an immense cost to society in the form of massive and unnecessary pollution of lakes, rivers and Chesapeake Bay. Pollution resulting from land-application is quantitatively ignored in the JLARC report and submerged in verbiage in favor of agriculture by the Chesapeake Executive Council, EPA and CBF. I doubt that politicians would be elected if they advocated the existing government policy that “Continued profits for special interests (poultry growers, land-appliers and a few farmers) are more important than improving water quality in Chesapeake Bay.” Until people demand an end to cheap but highly polluting agricultural fertilization practices and are willing to shoulder the economic consequences for less polluting alternatives, resulting in more expensive poultry and food grown with mandated BMPs, there can be no significant improvement in water quality in Chesapeake Bay. Water quality in Chesapeake Bay cannot improve until the major source of pollution, agricultural fertilization, is addressed meaningfully.

Dr. Lynton S. Land, Emeritus Prof. Geological Sciences, U. Texas, Austin

P. O. Box 539, Ophelia VA 22530, October 14, 2006