EFFECT OF CHEMICAL FERTILIZER ON METHANE EMISSION FROM RICE PADDIES

Using the closed chamber method, the methane emission rate from rice p addies was measured during three complete vegetation periods from 1990 to 1992 in the Beijing area. The emission level of this region was fo und between 15.0 mg/m2/h and 20.4 mg/m2/h. The methane emission rate s howed a strong diurnal variation with the maximum and minimum emission rate in the afternoon and in the morning, respectively. The diurnal m ethane emission rate closely correlated with soil temperature after th e tillering stage. A study on the effect of four kinds of chemical fer tilizers (ammonium sulfate, urea, ammonium phosphate, ammonium bicarbo nate) was carried out in 1991 and 1992. Application of ammonium sulfat e and urea resulted in a reduction of methane emission, while applicat ion of ammonium phosphate enhanced the methane emission during the eff ective period of a chemical fertilizer. No significant influence of am monium bicarbonate was found. Reasonable application of some types of chemical fertilizers in 1992 resulted in a significant reduction of to tal methane emission from rice paddies.