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This article in JEQ

  1. Vol. 23 No. 3, p. 437-451
     
    Received: Aug 9, 1993
    Published: May, 1994


    * Corresponding author(s):
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doi:10.2134/jeq1994.00472425002300030006x

Managing Agricultural Phosphorus for Protection of Surface Waters: Issues and Options

  1. Andrew N. Sharpley *,
  2. S. C. Chapra,
  3. R. Wedepohl,
  4. J. T. Sims,
  5. T. C. Daniel and
  6. K. R. Reddy
  1. USDA-ARS, National Agric. Water Quality Lab., P.O. Box 1430, Durant, OK 74702-1430;
    CADSWES, Univ. of Colorado, Boulder, CO 80309-0421;
    Wisconsin Dep. of Nat. Resources, Madison, WI 53707;
    Dep. of Plant Science, Univ. of Delaware, Newark, DE 19717-1303;
    Dep. of Agronomy, Univ. of Arkansas, Fayetteville, AR 72701;
    Soil Science Dep., Univ. of Florida, Gaineseville, FL 32611.

Abstract

Abstract

The accelerated eutrophication of most freshwaters is limited by P inputs. Nonpoint sources of P in agricultural runoff now contribute a greater portion of freshwater inputs, due to easier identification and recent control of point sources. Although P management is an integral part of profitable agrisystems, continued inputs of fertilizer and manure P in excess of crop requirements have led to a build-up of soil P levels, which are of environmental rather than agronomic concern, particularly in areas of intensive crop and livestock production. Thus, the main issues facing the establishment of economically and environmentally sound P management systems are the identification of soil P levels that are of environmental concern; targeting specific controls for different water quality objectives within watersheds; and balancing economic with environmental values. In developing effective options, we have brought together agricultural and limnological expertise to prioritize watershed management practices and remedial strategies to mitigate nonpoint-source impacts of agricultural P. Options include runoff and erosion control and P-source management, based on eutrophic rather than agronomic considerations. Current soil test P methods may screen soils on which the aquatic bioavailability of P should be estimated. Landowner options to more efficiently utilize manure P include basing application rates on soil vulnerability to P loss in runoff, manure analysis, and programs encouraging manure movement to a greater hectareage. Targeting source areas may be achieved by use of indices to rank soil vulnerability to P loss in runoff and lake sensitivity to P inputs.

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