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This article in JEQ

  1. Vol. 36 No. 5, p. 1235-1240
    Received: Dec 20, 2006

    * Corresponding author(s): rmaguire@vt.edu
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Diet Modification to Reduce Phosphorus Surpluses: A Mass Balance Approach

  1. R. O. Maguire *a,
  2. D. A. Crouseb and
  3. S. C. Hodgesa
  1. a Dep. of Crop and Soil Environmental Sciences, Virginia Tech, Blacksburg, VA 24061
    b Dep. of Soil Science, North Carolina State Univ., Raleigh, NC 27695


Diet modification to reduce phosphorus (P) concentrations in manures has been developed in response to environmental concerns over P losses from animal agriculture to surface waters. We used USDA-NASS statistics on animal numbers and crop production to calculate county scale mass balances for manure P production, P removed in harvested portion of crops, and the potential effects of diet modification. Although spreading manure evenly over all crop acreage within a county is unlikely to occur, these calculations give a good indication as to the impact diet modification to reduce P can have at a regional or national scale. There was a high degree of regional variability in manure P surpluses (e.g., with the large crop acreages in the grain belt leading to large P offtake in crops preventing most P surpluses). In 89% of counties, there was a deficit of manure P relative to crop P removal; therefore there was a manure P surplus in 11% of counties. Diet modification decreased the percentage of states with a manure P surplus from 11 to 8%, a decrease of approximately 27%. Diet modification decreased the percentage of counties with the greatest surpluses of manure P (>30 kg ha−1) from 3% of all counties to 1%. Diet modification to decrease manure P is an important part of strategies to alleviate environmental concerns associated with surplus manure P in many areas, but additional strategies to deal with manure P surpluses are needed in some areas.

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Copyright © 2007. American Society of Agronomy, Crop Science Society of America, Soil Science SocietyAmerican Society of Agronomy, Crop Science Society of America, and Soil Science Society of America