FATE OF [C-14] HYDROQUINONE AND [N-15]UREA IN A SOIL RICE SYSTEM - A POT TRIAL

[N-15]-urea and [C-14]hydroquinone were applied to brown soil (Agrodolf) at rates of 61.33 mug N g- 1 soil and 533.2 ng hydroquinone g-1 soil respectively in a rice pot trial. Total C-14-materials and isolated [C-14]hydroquinone in rice and soil were determined. The results showed the rice plant absorbed 0.25% of the [C-14]hydroquinone added and of this, only 34 and 47 ng g-1 existed in the form of hydroquinone in refined rice grain and straw, respectively. Most of the absorbed [C-14]hydroquinone had been degraded or converted to other forms of C-14-materials in plant tissues. In soil, the [C-14]hydroquinone decomposition rate was found to be 86.6% and about 58% of the added [C-14]hydroquinone was degraded and could not be detected; it contained 72 ng [C-14]hydroquinone g-1 soil (average) after 3 months of rice growth, much lower than its Multimedia Environmental Goal. The effects of hydroquinone on promotion of rice yield and urea efficiency were not observed in this pot trial due to the special experimental conditions. It is concluded that applying appropriate concentration of hydroquinone with urea as a urease inhibitor will not produce harmful effects on human health and the environment.