3,4-Dimethylpyrazole phosphate and 2-(N-3,4-dimethyl-1H-pyrazol-1-yl) succinic acid isomeric mixture nitrification inhibitors: Quantification in plant tissues and toxicity assays.

Nitrification inhibitors are used to maintain ammonium available in the soil for longer periods while reducing nitrate leaching and N2O emission. In this work we evaluated the potential toxicity effects of 3,4-dimethylpyrazole phosphate (DMPP) and 2-(N-3,4-dimethyl-1H-pyrazol-1-yl) succinic acid isomeric mixture (DMPSA) nitrification inhibitors. In order to determine the potential plant capacity to take up and translocate these inhibitors, we grew clover plants in hydroponic conditions and we developed a novel methodology for extracting DMPP and DMPSA that we quantified by HPLC. In addition, we also did toxicity bioassays: seed germination and Vibrio fischeri test. When clover was exposed to high amounts of nitrification inhibitors, plants accumulated DMPP, predominantly in leaves, and also DMPSA that preferentially accumulated in roots. These inhibitors did not provoke phytotoxicity at the equivalent of the maximum amount estimated in agriculture (0.5mg/kg soil). DMPP only provoked detrimental effects in plants at very high dose (100mg/kg soil). Interestingly, DMPSA was innocuous.