Researchers Working with Regulators & Growers to Calculate Accurate Loading Rates

Restoration efforts in the Chesapeake Bay recently intensified with the 2010 introduction of federal Total Maximum Daily Load (TMDL) limits for all 94 bay watershed segments.  These regulations have specific, binding consequences if any of the six states or the District of Columbia fail to meet interim goals, including loss of federal dollars for various programs and increasing regulation of point sources, if non-point (agricultural and urban) nutrient reduction goals are not met in the watershed.   An expert agricultural review panel was  recently formed to advise how the precision of the Chesapeake Bay model can be increased, through a better understanding of agricultural practices, including precision nutrient and water management and many other best management practices employed by growers.  This information will guide both current and future model development, to increase the accuracy of the model.  The nursery and greenhouse industry poses several unique characteristics compared to general agriculture, which must be accounted for in order to produce a more precise estimate of loading rates.  A more accurate accounting of land area by operation type is a primary issue, since the current model relies on USDA agricultural census data, which does not match well with operational production on the ground. This is very important since the type of operation (field, container-nursery, or greenhouse operation) has a significant impact on plant density, types of fertilizer used and application rate, which combine with irrigation and water management practices to affect nutrient runoff potential.  It is also important to represent a variety of implemented best management practices, such as slow-release fertilizers, in-row buffer strips, and containment in the model, and accurately assess how these mitigate both nutrient and sediment runoff from individual operations.  It is possible that the TMDL process currently being implemented throughout the Chesapeake Bay will be used as a remediation process for other impaired waterways in the future.  Information learned from the Chesapeake Bay TMDL process could be applicable to other estuarine water bodies, which have similar water-use regulations and issues.  The lessons learned about the Chesapeake Bay model in general, and for the nursery and greenhouse industry in particular, will likely provide guidance for how industry can be proactive in reducing environmental impacts and protect the economic viability of growers in the future.