Development of a Research-based Phosphorus Index for Vermont. (NE_03-jokela104504-oral)
Authors:
W.E. Jokela* - Univ. of Vermont J.P. Tilley - Univ. of Vermont F.R. Magdoff - Univ. of Vermont F. Potter III - USDA-NRCS
Abstract:
The P Index is a tool developed to assess the potential for P runoff from individual fields based on soil and field characteristics and management practices. Our current P Index is a modification of the LeMunyon and Gilbert prototype based on minimal state or regional data or evaluation. We began our 8-month revision process by establishing a multi-agency work group to support and advise the core development team, examining P Indexes from other states, and reviewing P runoff research results from current and past research in VT and elsewhere. We decided to pursue two approaches. One uses the same format as that used in VT and most NE states in which the sum of P source factors (soil test P, manure, and fertilizer P) are multiplied by a composite factor for transport (erosion, runoff, flooding, etc.). The other is a semi-quantitative method that estimates actual P loss via two different pathways, particulate P from erosion and dissolved P via runoff. The initial revised drafts were examined by comparing to the current VT P Index and to those of other states in the NE, calculating the PI on a data set of 300 actual fields, conducting a sensitivity analysis for various input parameters, and, for the pathway PI, comparing estimated P loads to those from measured watershed studies. Local and regional field visits/assessments contributed further input. Release of the revised P Index will be followed by training, publication of extension materials, and incorporation of the revised P Index into nutrient management software.
Speaker Information: William Jokela, Univ. of Vermont, Plant and Soil Science Dept, Hills Bldg. Univ. of, Burlington, VT 05405; Phone: 802-656-0480; E-mail: [email protected]
