— Poultry litter example – The current model assumes that as much as 15% of poultry litter is dropped during clean out of chicken houses. (During a clean out the sawdust bedding that catches chicken waste is scooped using a skid loader and driven from the house across a concrete pad at the end of the house and deposited in a nearby poultry litter storage shed.) Fifteen percent of the litter would mean an entire tractor trailer load is dropped on the ground and left during this process. Recent scientific research conducted at the University of Delaware found that less than a wheel barrel load actually falls off the skid loader in the process and most of that is swept up afterwards. This error is huge and is one that makes farmers distrust the model output. If left unfixed, the model will calculate a much higher level of potential nitrogen and phosphorous runoff than is actually occurring on farms. All the BMPs installed will be credited towards making up for an N&P loss that is not actually occurring.
Multiple practice exclusion - The most recent update of the model may not credit multiple Best Management Practices on the same field. We have been told that this will not be fixed. If this is the case, farmers might as well throw in the towel now. Most farms use cover crops, no-till planting, riparian buffers and grassed waterways all on the same field. All have benefit and all work to keep the vital nutrients in our field and out of the Bay. Farmers certainly wouldn’t spend money to install practices if they were not useful in preventing loss of nitrogen or phosphorus. But the Bay Model may not give farmers credit for all the work they are doing. We haven’t seen the latest version but we have heard this is the case with the model that will be used to dictate the numbers that must be reached for the TMDL.