Submitted to: Irrigation Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/17/2016
Publication Date: 3/21/2016
Publication URL: http://handle.nal.usda.gov/10113/62581
Citation: Mclaughlin, M.R., Brooks, J.P., Adeli, A., Jenkins, J.N. 2016. Improving estimates of N and P loads in irrigation water from swine manure lagoons. Irrigation Science. 34(3):245-260.
Interpretive Summary: Nutrient management plans for confined animal feeding operations must track nitrogen (N) and phosphorus (P) loads from land-applied manure, including irrigation water from lagoons. By state regulation in Mississippi, nutrient records from manure lagoon irrigation water must be based on at least one analysis of the lagoon water annually; however, the present study showed that nutrient estimates based on a single annual analysis may over- or under-estimate N and P. The research reported here also confirmed that N and P levels in lagoon water, and the N:P ratio, varied significantly, but predictably, during the year, with seasonal changes in lagoon water temperature thought to be the driving force. The report showed that the predictable variation could be described by a simple mathematical model. The model was then applied to develop easy-to-use, calendar-based, lagoon-specific tables of N and P levels for lagoon water for any given day of the irrigation season. The tables enabled the land nutrient manager to more accurately track land-applied N and P loads from irrigation events throughout the irrigation season. This report describes the development and use of these improved methods for more precisely estimating N and P loads in irrigation water from a swine manure lagoon in Mississippi and also uses published data from earlier studies to examine the feasibility of applying these methods to swine manure lagoons in North Carolina.
Technical Abstract: The implementation of nutrient management plans (NMPs) for confined animal feeding operations (CAFOs) requires recording N and P loads from land-applied manure, including nutrients applied in irrigation water from manure treatment lagoons. By regulation, lagoon irrigation water nutrient records in Mississippi must be based on at least one lagoon water nutrient analysis annually. Research in Mississippi has shown that N and P levels in lagoon water, and the N:P ratio, vary significantly through the year. Nutrient estimates based on one annual analysis do not account for this variability and may overestimate or underestimate N and P loads. The present study reports an improved method to more precisely estimate N and P loads in irrigation water from swine manure lagoons. The method is based on predicable annual cycles of N and P levels in lagoon water and employs simple curve-fitting of lagoon-specific formulas derived by analyses of historical data. Similarity of curves from analyses of Mississippi lagoons and other lagoon studies suggests that the method can be applied using the often limited nutrient data for a lagoon to more precisely estimate seasonal shifts of N and P and to improve the precision of estimates for N and P in irrigation water. Although the present study focused on swine manure lagoons in the southern US, recognition that the annual N cycle in lagoon water is temperature driven, suggests that additional research incorporating temperature into future models could extend these models to other types of waste treatment lagoons and climates.