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This article in JEQ

  1. Vol. 30 No. 5, p. 1699-1709
    Received: Nov 15, 2000

    * Corresponding author(s): jdc7@psu.edu
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Leachate Chemistry of Field-Weathered Spent Mushroom Substrate

  1. Mingxin Guo,
  2. Jon Chorover *,
  3. Rex Rosario and
  4. Richard H. Fox
  1. Department of Agronomy, The Pennsylvania State Univ., University Park, PA 16802


Passive leaching by rainfall and snowmelt is a popular method to treat piles of spent mushroom substrate (SMS) before its reuse. During this field weathering process, leachate percolates into the underlying soils. A field study was conducted to examine the chemistry of SMS leachate and effects of infiltration. Two SMS piles were deposited (90 and 150 cm in height) over a Typic Hapludult and weathered for 24 mo. Leachate was collected biweekly using passive capillary samplers. The SMS leachate contained high concentrations of dissolved organic carbon (DOC; 0.8–11.0 g L−1), dissolved organic nitrogen (DON; 0.1–2 g L−1), and inorganic salts. The pH, electrical conductivity, and acid neutralizing capacity were 6.6 to 9.0, 21 to 66 ds m−1, and 10 to 75 mmolc L−1, respectively. Inorganic chemistry of the leachate was dominated by K+, Cl, and SO2− 4 Leachate DOC was predominantly low molecular weight (<1000 Da) organic acids. During 2 yr of weathering, the 90-cm SMS pile released (per cubic meter of SMS) 3.0 kg of DOC, 1.6 kg of dissolved N, and 26.6 kg of inorganic salts. The 150-cm pile released (per cubic meter of SMS) 2.8 kg of DOC, 0.7 kg of dissolved N, and 13.6 kg of inorganic salts. The 150-cm pile retained more water and exhibited lower net nitrification compared with the 90-cm pile. The top 90 cm of soil retained 20 to 89% of the leachate solutes. Weathering of SMS in piles of 90 cm depth or greater may adversely affect ground water quality.

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Copyright © 2001. American Society of Agronomy, Crop Science Society of America, Soil Science SocietyPublished in J. Environ. Qual.30:1699–1709.