Agriculture Best Management Practice Efficiencies Accepted for the
Inland Bays Watershed

By Jennifer Jennings

The efforts of the Agriculture Pollution Control Strategy Workgroup were well rewarded on December 9, 2003 at the full committee meeting of the Delaware Nutrient Management Commission (DNMC).  The Agriculture PCS Workgroup, formed in April 2002, is a multi-agency “think tank.”  Representative agricultural experts came from two Department of Natural Resources and Environmental Control (DNREC) divisions --- Water Resources and Soil and Water Conservation, the National Resource Conservation Service (NRCS), the Kent and Sussex Conservation Districts, the University of Delaware, and the Delaware Nutrient Management Commission.  The ultimate goal of this group was to develop a method of estimating the contribution of existing agricultural best management practices (BMPs) toward achieving the TMDL mandated nutrient load reductions for the Inland Bays.

A TMDL, or total maximum daily load, is the maximum amount of a pollutant that can enter a water body without having a detrimental effect on the water quality.  The Inland Bays TMDL, which addresses the nutrients nitrogen and phosphorus, was adopted in December 1998.  In order to reduce the nutrient loads to the estuary, it was determined that all point sources, like wastewater treatment plants, had to be removed and that the nutrients coming from nonpoint sources, which originate from various land use practices, must be reduced.  The requirements of the TMDL will be achieved through the implementation of a pollution control strategy (PCS).   The Inland Bays Tributary Action Team (TAT) and DNREC are currently in the process of developing a PCS for the Inland Bays.  The TAT recommended aggressive tactics to deal with nonpoint nutrients from on-site wastewater disposal systems, stormwater, and urban land uses, and also called for agreement between state, county, and local environmental laws.  The TAT initially decided not to address the agricultural sector in their recommendations because the state was in the process of passing the Nutrient Management Act (NMA) and forming the Nutrient Management Commission (NMC) to specifically address the role of agriculture in the nutrient story at that time (1998).  The PCS currently under development, however, will not be complete without an agricultural component.

The need for assessing agriculture’s contribution to the required TMDL nutrient reductions, by way of implementing BMPs, was the impetus for forming the Agriculture PCS Workgroup more than a year and a half ago.  By estimating how well the BMPs currently used on farms in the watershed are at reducing the nutrient load from agricultural lands, goals can be established for further implementation of the most effective practices.  This goal can thus serve as the agricultural component of the strategy.  The workgroup compiled and analyzed research reports and data sets appropriate to the Inland Bays watershed in order to assign reduction efficiencies to BMPs that ranged from wetlands and stream buffers to poultry litter management and the use of nutrient management plans.

The workgroup found that cover crops, poultry litter relocation, and nutrient management plans have been the most effective practices for nitrogen reductions to date in the Inland Bays watershed.   The greatest phosphorus reductions have come from the addition of the enzyme Phytase to poultry feed, which reduces the phosphorus content in excrement, and the litter relocation and alternative use programs.   These and other agriculture BMPs have already helped achieve more than 10% of the needed nitrogen reduction and close to 60% of the required phosphorus reduction.  Thus, the agricultural sector’s commitment to improving the water quality of the Inland Bays appears to have resulted in substantial nutrient reductions thus far.

Some of the practices that are most effective at reducing nutrients, however, are not currently in wide spread use across the Inland Bays watershed.  Virtually every agriculture BMP can be implemented at no or very low cost (per acre) to the farmer with the help of cost-share programs.  In addition, these practices are a much more cost effective means of achieving nutrient reductions in comparison to wastewater and stormwater retrofit projects.  Thus, the agricultural community has a great opportunity to add to the tremendous effort already put forth by establishing goals for future agriculture BMP implementation.

At the December 9th meeting of the Nutrient Management Commission, the Workgroup presented their findings on agriculture BMP efficiencies, progress to date from the agriculture sector toward the TMDL reductions, and goals for future implementation of the more effective agriculture practices.  By the close of the meeting, the Committee endorsed the Workgroup’s assessment of BMP efficiencies and the concept of developing implementation goals for each sector contributing nutrients to the Inland Bays.  With this endorsement, the State of Delaware is now ready to propose a complete and comprehensive Pollution Control Strategy for the Inland Bays watershed, the first in the state.