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ARS Home » Northeast Area » University Park, Pennsylvania » Pasture Systems & Watershed Management Research » Research » Publications at this Location » Publication #174821
Title: LOCAL ASSESSMENTS OF THE IMPACT OF P-INDEX IMPLEMENTATION IN PENNSYLVANIA

Author
item KOGELMANN, W - PENN STATE UNIV
item Bryant, Ray
item LIN, H - PENN STATE UNIV
item BEEGLE, D - PENN STATE UNIV
item Weld, Jennifer

Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/25/2005
Publication Date: 1/15/2006
Citation: Kogelmann, W.J., Bryant, R.B., Lin, H.S., Beegle, D.B., Weld, J.L. 2006. Local assessments of the impact of phosphorus index implementation in Pennsylvania. Journal of Soil and Water Conservation. 61:20-30.

Interpretive Summary: Nutrient loading of streams and lakes is a leading cause of surface water impairment in Pennsylvania. To address this problem, the Pennsylvania State Conservation Commission has proposed the adoption of the Phosphorus (P) Index in forthcoming revisions of the Pennsylvania Nutrient Management Act regulations. Thirteen farms in Lancaster and Snyder Counites were studied to provide insight into the impact of P-Index implementation in regions that were previously identified as having a high fraction of farmland that will be most affected by these regulations. Of the 276 fields studied, 29.7% required detailed assessment by the P Index, and 67.1% of those fields were found to be 'P restricted' under current management practices. From a whole farm management perspective, a rating of 'P restricted' on an agricultural field limits additional manure applications, which may require the purchase of commercial fertilizers to meet nitrogen demands. Additionally, disposal of manure by land application will be concentrated on other fields. Overall, 19.9% of the fields in this study (representing 26.8% of total farm acreage) would be P restricted under the P-Index. Soil test P levels were found to increase with increasing animal density and farms in the highest animal density classes were found to have the largest fraction of fields and acreage restricted. Thus, larger scale generalizations, while useful on a regional basis for planning purposes, may not hold for individual farms or fields and may not reflect the full impact of nutrient management regulations at the local level.

Technical Abstract: Phosphorus (P), while essential for profitable agriculture poses a threat to water quality if it is transported from agricultural operations to waterways in concentrations and quantities sufficient to stimulate algal growth. Nutrient loading of streams and lakes is a leading cause of surface water impairment in Pennsylvania. To address this problem, the State Conservation Commission (SCC) has proposed the adoption of the Phosphorus Index (P-Index) in forthcoming revisions of the PA Nutrient Management Act regulations. The P-Index is a field-level assessment tool that rates fields on their potential to lose P to surface waters. Based on the P-Index rating, P application restrictions may be recommended. Farm operators may need to alter manure application practices in terms of amount, location, method, and timing which will carry a cost in both time and money. The degree of this burden should be investigated prior to implementation. To this end, the SCC funded a two phase study to assess the impact of P-Index implementation in Pennsylvania. This report contains the results of Phase II of this research. Thirteen farms in Lancaster and Snyder Counites were studied to provide insight into the impact of P-Index implementation in regions that were identified (in Phase I) as having a high fraction of farmland requiring Part B assessment under the P-Index. Of the 276 fields studied, 29.7% required Part B assessment, and 67.1% of the fields requiring Part B were found to be P restricted under current management practices. Overall, 19.9% of the fields (representing 26.8% of total farm acreage) would be P restricted under the P-Index. Soil test P levels were found to increase with increasing animal density and farms in the highest animal density classes were found to have the largest fraction of fields and acreage restricted. A number of variables and combinations of factors can lead to high P-Index values. Thus, larger scale generalizations, while useful on a regional basis for planning purposes, may not hold for individual farms or fields. Lastly, degree of soil saturation with P (Psat) was assessed on the fields sampled. Psat of 21% corresponded to the 200 ppm P threshold that is part of the P-Index. Soils from Lancaster County in the Piedmont physiographic region were found to have significantly higher P sorbing capacity compared to soils in Snyder County which is in the Ridge and Valley physiographic region. Psat was highest in samples from animal concentration areas (mean of 40%) compared to cropland (11%) and pastureland. (11%). This level of Psat is near twice the 21% level associated with the 200 ppm P environmental P threshold, indicating that these areas pose a significant environemental threat if runoff is not properly managed.