Abstract
Revolving furnace slag (RFS), which is and industrial by-product, and spent disposable portable body warmer (PBW) were applied to paddy soil as oxidation materials. Portions of 4 kg of Coarse and Medium Textured Gley soil were placed into plastic pots (1/5,000a). RFS was added to the pots at the rate of 0 (control), 10,20,40,100 ton ha^<-1>, and PBW at 10 ton ha_<-1>only. Methane flux from the potted soil planted with rice was measured by the closed chamber method during the 1999 cropping season. Pots that received RFS showed lower. Eh values compared with the control pot, although the RFS was applied to keep soil oxidative in the early period of cultivation. The strong decrease in Eh under a high rate of RFS application may be due to the high pH of the RFS (pH (H_2O) = 12.2). On the other hand, methane flux was suppressed under a high rate of RFS application, during the early period of cultivation. However, this flux trend was reversed during the midgrowing period. This may be due to disturbances in the soil environment caused by dissolving elements from RFS. Total methane flux during the cultivation period was significantly decreased, about 10%, when 10-40 ton ha^<-1>of RFS and 10 ton ha^<-1> of PBW were applied. Methanogenic activity was not significantly different when 0-40 ton ha^<-1> of RFS were applied, while that of RFS pots at 1OO ton ha^<-1> and of PBW pots at 10 ton ha^<-1> were decreased. However, methane oxidizing activity was increased, max 15%, when 10-40 ton ha^<-1> of RFS were applied, while that of RFS pots at 1OO ton ha^<-1> and of PBW pots at 1O ton ha^<-1> were decreased. The decrease in total methane flux may be attributed to enhanced methane oxidizing activity rather than inhibition of methanogenic activity. The grain yield was significantly increased, about 30%, when 40 or 1OO ton ha^<-1> of RFS was applied. It was also partly due to the dissolving inorganic substances from RFS. From this study it is clear that the use of RFS and PBW in paddy field are desirable because they led to increased grain yield as well as decreased methane emission.
