Richard E. Miller, H. W. Anderson, D. Young
1988
Citations
1
Influential Citations
7
Citations
Journal
Soil Science Society of America Journal
Abstract
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.