Effects of copper concentration on methane emission from rice soils

Outdoor pot experiments with various paddy soils representing five soil types were conducted at Nanjing Agricultural University during the 2000 and 2001 rice-growing seasons. Eighteen soils and ten out of the eighteen soils were involved in the 2000 and the 2001 experiment, respectively. Two treatments were designed as mineral fertilization (MF) and mineral fertilizer + wheat straw incorporation (MF + WS) for the 2001 experiment. Seasonal average rate of CH 4 emission from different soils ranged from 1.96 to 11.06 mg m −2 h −1 in the 2000 experiment, and from 0.89 to 5.92 mg m −2 h −1 for the MF treatment in the 2001 experiment, respectively. Incorporation of wheat straw enhanced considerably CH 4 emission with an average increment of 7.09 mg m −2 h −1. CH 4 emissions from the two-year experiment were negatively correlated to soil available and total copper concentration. A further investigation showed that CH 4 emission from the MF treatment was positively related to the dissolved organic carbon (DOC) in the soil ( r=0.904, p