Thursday, March 26, 2015

The Eastern Shore, Chicken Manure and the TMDL

from USGS
According to the U. S. Environment- al Protection Agency (EPA), the primary pollutants in the Chesapeake Bay and its tributaries are; nitrogen, phosphorus and sediment. These nutrients can lead to harmful algae blooms that kill underwater plants and destroy the river, bay and estuary habitat that aquatic life needs to survive. Excess nutrients and sediments can also lead to water with little or no dissolved oxygen to the detriment of aquatic life and the ecosystem. Although the Eastern Shore includes only 7% of the land area in the bay watershed, it releases 25% of total phosphorus loads to the bay from manure and 33% of phosphorus loads from fertilizer applications. (This excludes the phosphorus from human waste water treatment.)

Phosphorus can be found dissolved in the soil solutions in extremely low concentrations or associated with soil minerals or organic materials. The relative amounts of each form of phosphorus will vary among soils. The soils of the Eastern Shore are not contusive to retaining dissolved phosphorus and the excessive levels of phosphorus applied to the land are carried into the surface waters. Over application of phosphorus is caused by the use of manure from the concentrated poultry feed operations. Poultry typically has nearly equal concentrations of phosphorus and nitrogen, though crops typically require 2.4-4.5 times the nitrogen as phosphorus. Poultry manure is used as fertilizer in the region to avoid the costs of waste removal or treatment. Historically, poultry manure has been added to soils obtain the correct nitrogen content not the lower phosphorus needs. The excess phosphorus is released through runoff and erosion. Pig manure has slightly more nitrogen than phosphorus. Cow manure has typically twice the nitrogen as phosphorus and is much less of a problem when used as fertilizer.

To restore the waters of the Chesapeake Bay the EPA has put the entire 4,247 square miles of the Chesapeake Bay watershed on a pollution diet. The Chesapeake Bay pollution diet, the Total Maximum Daily Load (TMDL) of nitrogen, phosphorus and sediment was mandated by the EPA to the six Chesapeake Bay Watershed states (Virginia, Maryland, Delaware, New York, Pennsylvania and West Virginia) and the District of the Columbia. Throughout the region the nitrogen, phosphorus, sediment and other pollutants are carried to the Chesapeake Bay by stormwater runoff.

A new report from the U.S. Geological Survey, “Understanding Nutrients in the Chesapeake Bay Watershed and Implications for Management and Restoration—the Eastern Shore,” by Scott W. Ator and Judith M. Denver highlights the contribution of the Eastern Shore to the nutrient pollution problem. Though only a small area of the Chesapeake Bay watershed, the Eastern Shore contributes disproportionately large loads of the excess nitrogen and phosphorus that have contributed to ecological and economic degradation of the bay in recent decades.

The disproportionately large releases of nitrogen and phosphorus to the Chesapeake Bay from the Eastern Shore are attributable to both human farming and agricultural practices as well as natural hydrogeologic and soil conditions. Land application of poultry manure and use of fertilizers is intensive on the Eastern Shore. Also, hydrogeologic and soil conditions promote the movement of these compounds from application areas on the land surface to groundwater and surface waters; and the proximity of much of the Eastern Shore to tidal waters limits natural removal and depletion of these compounds. The Eastern Shore represents only 7% of the Chesapeake Bay watershed land area, but receives nearly twice as much nitrogen and phosphorus applications per acre as other part of the watershed, and a significant portion is released to the bay.
from USGS

The Eastern Shore has been primarily agricultural for several hundred years. Nearly 600 million chicken are produced each year on the eastern shore more than half in Maryland, most of the remainder in Delaware. There are also crops grown in the region. Using applications of nitrogen and phosphorus to fertilize the land increased substantially during the second half of the 20th century, but use of fertilization has since stabilized or decreased while agricultural production has continued to increase.

Once applied to the land as either fertilizer or manure, nitrogen and phosphorus are carried primarily by runoff (stormwater or irrigation) to the surface waters. On the Eastern Shore, nitrogen is primarily transported to surface waters through groundwater in the form of nitrate, and phosphorus transported primarily in overland runoff. Here is where the hydrology and geology of the Eastern Shore region made everything worse. The naturally high oxygen containing groundwater and soil allowed for the uptake and storage of excessive nitrogen in the groundwater of the Eastern Shore. The USGS reports that 70% of nitrogen in the local streams is delivered through groundwater as nitrate and it will take decades to dissipate even if current use is significantly curtailed. Phosphorus, conversely, is predominantly transported over the land in runoff attached to sediment. Applications of phosphorus to farmland in recent decades have far exceeded the amounts necessary for crop growth. Thus, phosphorus has increased in the environment. Unlike nitrate, phosphorus is relatively insoluble in water and so excess phosphorus generally accumulates in agricultural soils. The only way to remove it is the slow take up of phosphorus by plants or by erosion of the soil carrying the phosphorus into the bay.

On the Eastern Shore, nitrogen is common in groundwater and surface waters and phosphorus is common in surface waters at concentrations that are well above natural levels, and are among the highest in the Nation. The increasing nitrate concentrations over time largely reflect the increasing nitrogen applications in previous decades and the long time periods required for the movement of nitrate in groundwater to flow to surface waters.

Soils and surface water sediments are sandy and permeable over much of the area—conditions that promote the movement of nutrients from application areas to groundwater, streams, and tidal waters. Agricultural best management practices need to be designed specifically for the regions. Te land application of phosphorus needs to be reduced (or eliminated for a period of years) and tightly controlled in the future and that means addressing the problem of poultry manure. Any solution will increase the costs involved in raising chicken and producing eggs. Ultimately it means that the cost of those food products will go up either directly or through some other means.

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