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This article in SSSAJ

  1. Vol. 52 No. 1, p. 256-260
    Received: June 23, 1986

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Urea and Biuret Stimulate Growth of Douglas-fir and Western Hemlock Seedlings

  1. Richard E. Miller ,
  2. Harry W. Anderson and
  3. Donald C. Young
  1. USDA-FS, Forest Science Lab., Olympia, WA
    Washington State Dep. of Natural Resources, Olympia, WA
    Unocal Science and Technology Div., Brea, CA



Two experiments were conducted in a greenhouse to test a theory that biuret in urea fertilizer reduces growth of Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] or western hemlock [Tsuga heterophylla (Raf.) Sarg.]. Newly germinated seedlings in 2.5-L pots were treated with 0, 0.224, 2.24, or 22.4 kg biuret ha−1 (40% N) in factorial combinations with 0, 84, or 168 kg N ha−1 as reagent-grade urea (46% N). The biuret was applied as a solution to either the sandy loam soil or the foliage. Four of the eight replicates were harvested 203 d after treatment. For Exp. 2, the remaining seedlings were retreated as they were initially and harvested 305 d later. In both experiments, the two species responded strongly to urea; moreover, seedling dry weight increased with increasing biuret (P = 0.003). Averaged over all other factors, weight of seedlings treated with the highest biuret dosage was 14% more than the weight of seedlings with no biuret. Unfertilized hemlock responded as much to 0.2 kg biuret ha−1 (0.08 kg N ha−1) as to 84 kg N ha−1 as urea; this suggests that biuret functions as a hormone. The results indicated that biuret is unlikely to reduce growth of seedlings of either species even when urea heavily contaminated with biuret is applied at high dosage.

Contribution from the USDA-FS, Pacific Northwest Res. Stn., Olympia, WA 98502.

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