稻田CH_4排放的控制措施

通过对稻田CH_4排放施肥效应的研究指出:化肥的施用能够降低CH_4的排放,但是有机物的数量及质量是影响稻田CH_4排放的主要因素,因此稻田CH_4排放的控制应该主要从有机肥的科学施用入手;比起常规的有机肥,沼渣肥这种已经发酵的“陈”有机肥能够较大程度地降低CH_4排放。推出沼渣肥和化肥混施的方案,在不降低水稻产量的同时降低CH_4排放,并建议新鲜有机肥(紫云英、稻草、猪粪等)先进沼气池产生沼气并利用,沼渣在施入土壤前先充分干燥。 水管理实验发现,当土壤湿润度低到一定程度时(26％<湿度<31％),CH_4排放率突然减少,CH_4产生率也明显降低,而且主要的产CH_4区域向土壤深处移动。重新灌水后在较长的一段时间内CH_4排放率仍不能恢复。一个三日间隔灌溉法因为灌溉的时间间隔太短,没有起到降低排放的作用。同时考虑水稻产量及方案实用性,提出用适当时间表的间歇灌溉来降低CH_4排放。如果能控制好土壤湿润度的临界值,我国常用的晒田技术会起到降低CH_4排放的效果。 为更好地降低CH_4排放,并努力增加水稻产量,设想了一种水肥结合的控制措施,即把沼渣肥和化肥混施方案与最简单的间歇灌溉方案——晒田共同使用、结果使晚稻CH_4排放降低了一倍多。水稻作为传输CH_4的主要路径,某些水稻品种也可能对降低稻田CH_4排

POSSIBLE MEASURES FOR THE REDUCTION OF METHANE EMISSION FROM RICE PADDY FIELDS

The study of fertilizer effect on CH₄ emssion from rice fields shows that the use of mineral fertilizer may reduce CH₄ emission. But the quantity and type of organic manure are considered to be the dominate factor affecting CH₄ emission,therefore the reduction of CH₄ emission should be mainly achieved by scientific application of organic manure. Compared to the normally used organic manure,the fermented and "old"sludge from biogas pits may greatly reduce CH₄ emission. Therefore we put forward a fertilization scheme combining sludge from biogas pits with mineral fertilizer to reduce CH₄ emission from rice fields while having no influence on rice production. We propose that before supplied to field, "fresh" organic matter (green manure,rice straw and pig excrement)had better be fermented in biogas pits for fuel substitute and be dried by storing in the open air.Water management experiments show that in the field treated with constant moisture, when soil moisture lowers down to certain extent(26%4 emission drops suddenly,and the main CH₄ producing area moves down to the deep soil. Even when flooded water was re-supplied to the dried field,CH₄ emission was not rising for a reasonably long period. A frequent drainage with 3-day -interval in our experiment doesn' t significantly lower down the total -season methaneemission. Taking rice production and practical use into account, we think a frequent drainage with a suitable time table should be used to reduce methane emission. If soil moisture can be controlled,sunning field technique,which is commonly used in our rice agriculture, may also be a good technique for lowering methane emission.In order to reduce CH₄ emission more efficiently and to increase rice production as well, we simulated a scheme in the late rice period (1992) combining fertilizer treatment which is the mixed use of fermented manure from biogas pits and mineral fertilizer, with water management which is the normal sunning ground technique,and we found that CH₄ flux may be reduced by more than 50%. A more scientific and practical measures combining fertilizer and water management needs further investigation.As a main routine for CH₄ transport,rice plant involves in CH₄ production and oxidation processes. Therefore some varieties of rice plants may play active role in reducing methane emission from rice fields.