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This article in JEQ

  1. Vol. 42 No. 2, p. 516-522
    Received: July 10, 2012
    Published: January 18, 2013

    * Corresponding author(s): cogger@wsu.edu
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Biosolids Applications to Tall Fescue Have Long-Term Influence on Soil Nitrogen, Carbon, and Phosphorus

  1. Craig G. Cogger *a,
  2. Andy I. Barya,
  3. Elizabeth A. Myhrea and
  4. Ann-Marie Fortunab
  1. a Washington State Univ. Puyallup Research and Extension Center, 2606 W. Pioneer Ave, Puyallup, WA 98371-4998
    b Dep. of Soil Science, North Dakota State Univ., Fargo, ND 58108-6050


Repeated applications of biosolids provide long-term benefits by increasing soil organic matter and N supply but can cause excess accumulation of P. Our objective was to determine the residual effects of repeated surface applications of biosolids on N availability and fate, tall fescue (Festuca arundinacea Schreb.) response, soil C, and P. A field experiment was started in 1993 to compare two biosolids products, each applied at three rates (6.7, 13.4, and 20.1 Mg ha−1 yr−1), with synthetic N fertilizer (0 and 403 kg N ha−1 yr−1 as ammonium nitrate). Treatments were surface applied for 10 yr, followed by a 9-yr residual period where all plots received a reduced rate of inorganic N (202 kg N ha−1 yr−1). Annual measurements included forage yield, N uptake, and soil nitrate N. Soil samples collected in 2002 and 2011 were analyzed for total C and N and Bray-1 P. Cumulative apparent N recoveries in harvested grass (1993–2010) were 51% for biosolids N and 72% for ammonium nitrate. Net fall soil nitrate N summed for the period 1993–2002 ranged from <1 to 3% of N applied. The N applied that was accounted for in forage and soil averaged 74% for biosolids and 73% for ammonium nitrate. Soil C increased in the biosolids treatments, and the increase was equivalent to 27% of biosolids C. Bray-1 P remained at excessive levels (338–629 mg P kg−1 soil) 9 yr after the last biosolids application.

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