Skip to main content

On-farm evaluation of a phosphorus site index for Delaware

Evaluaciónde un índice en un sitio de Fósforo para el estado de Delaware

Leytem, A.B. and Sims, J.T. and Coale, F.J. (2003) On-farm evaluation of a phosphorus site index for Delaware. Journal of Soil and Water Conservation. 58(2):89-97.

[img] PDF

Download (293kB)
[img] PDF

Download (11kB)


The contribution of phosphorus (P) to non-point source (N PS) pollution of surface
and groundwaters is a serious environmental problem in Delaware. In 1999, the Delaware
Nutrient Management Act was passed limiting application of P on "high" P soils to a "three year
crop removal" rate or to the amount recommended by a University of Delaware P site index. The
Delaware P site index was developed and evaluated on seven farms in Delaware, through a joint
effort between the universities of Delaware and Maryland. Results showed that 78% of fields
evaluated were in the "low" risk category, with the remaining 22% falling into the "medium"
(6%), "high" (7%), and "very high" (9%) risk categories. The components of the index found to
have the greatest influence on P site index ratings were soil erosion, subsurface drainage,
leaching potential, distance from field to surface water, soil test P and organic P application rates
and methods. P site index ratings were found to vary by year, depending on manure
applications, suggesting a need for yearly P site index evaluations or averages over a cropping
rotation. The P site index worked well for identifying fields with differing relative potential risks
of P loss; however, validation of these P loss assessments is needed to ensure that the risk
categories assigned are sufficiently protective of water quality. Continual monitoring, analysis,
and improvement of the P site index are needed to ensure that it remains a useful tool for P
based nutrient management planning in the future.

Item Type: Article
NWISRL Publication Number: 1101
Subjects: Mass Import - unclassified
Depositing User: Users 5 not found.
Date Deposited: 20 Nov 2010 21:50
Last Modified: 09 Nov 2016 16:15
Item ID: 160