| Abstract: | Abstract Herbicides have potential for economical and efficient site preparation following timber harvest. The effects of tebuthiu‐ron, one of the herbicides approved for this use, on soil nitrogen (N) mineralization and nitrification were determined in laboratory incubations. Tebuthiuron was added at rates from 0 to 1000 μg g‐1 to three soils. There was no effect of tebuthiuron additions of less than 1 μg g‐1 on soil N mineralization and nitrification. Tebuthiuron reduced nitrification in all soils at 1000 μg g‐1 and in two of the soils at 100 μg g‐1 . All soils had increased net mineralization with tebuthiuron added at 100 and 1000 μg g‐1. The addition of 50 μg NH+ 4‐N and 1000 μg tebuthiuron g‐1 resulted in increased net mineralization in the three soils. Nitrification was affected differently in each of the three soils by the addition of both NH+ 4‐N and tebuthiuron. The added NH+ 4‐N either removed the inhibition of nitrification by the herbicide or had no effect on the inhibition in two of the soils. In the third soil, nitrification was reduced by the addition of NH+ 4‐N. The presence of NO‐ 3‐N in these acid soils and the effects of added NH+ 4‐N on NO‐ 3‐N production suggest that heterotrophic nitrification occurs in at least two of the soils. The findings of this study indicate that any effects of tebuthiuron on N mineralization and nitrification at the currently recommended application rates are likely to be transient and localized. |
