Manure application rules and environmental considerations

Three manure application limits – nitrogen limit, annual phosphorus limit, and multiple-year phosphorus limit (P Banking) are modeled to compare economic profitability and probability of application prior to a runoff causing rainfall event. Particular attention is given to the number of hours needed and available to distribute manure under each limit. Benefits are estimated as the foregone fertilizer applications. Costs are estimated based on the hours needed for manure management. The benefit and cost estimates indicate that P Banking was more profitable than nitrogen limit, which was more profitable than annual phosphorus limit. The number of hours required indicated that the annual phosphorus limit would not be completed within a five-week window approximately 2 of 10 years. If further restrictions based on precipitation forecasts were imposed, the likelihood of completion decreased to 6 of 10 years. The results of the study indicate that regulations that require annual phosphorus limit of manure cost the farmer and may have the unintended consequence of increasing runoff. P Banking would be the preferred manure application rule for both increasing farmer net income and reducing probability of application prior to a runoff causing rainfall event.