开放式大气CO2浓度增高对水稻土反硝化活性的影响

利用江都市小记镇的稻-麦轮作FACE平台,研究大气CO2浓度增高对农田反硝化活性的影响.在2005年水稻生长季研究不同施肥(施常规氮量和低氮量)、不同秸秆还田(秸秆半还田、秸秆不还田)处理土壤中的反硝化细菌数量、硝酸还原酶和亚硝酸还原酶活性在大气CO2浓度升高(FACE)条件下随时间的变化情况,并且在拔节期测定对照及FACE土壤的反硝化潜势.结果表明:CO2浓度增高对水稻生长各时期的土壤反硝化细菌数量具有一定的抑制作用,这种抑制作用在常规氮肥施用及秸秆不还田情形下最为显著(P＜0.01).FACE对硝酸还原酶和亚硝酸还原酶活性几乎没有影响.对反硝化潜势的研究发现,在低氮与常氮施用条件下,FACE土壤的反硝化潜势分别为对照土壤的84.21%和97.46%.通过与土壤理化性质的相关性研究,认为主要是因为FACE促进植物生长和土壤中的微生物活性,反硝化微生物在竞争中受到抑制,使得反硝化活性降低.

Effects of FACE on denitrification activity in paddy-field soil

A free-air CO2 enrichment(FACE) experiment was used to investigate the effects of elevated atmospheric CO2 concentration on soil denitrification activities.The FACE system was conducted under a rice/wheat rotation at Jiangdu,China.The numbers of denitrifying bacteria,the activities of nitrate reductase and nitrite reductase was studied by sampling fresh soils from the fields with two different N fertilization levels(Usual N and Low N) and two rice straw incorporation levels [HR(half straw return) and NR(no straw return)] exposed to the elevated and ambient CO2 during the rice-growing season in 2005.And the denitrification potential was determined at jointing stage.The results showed that elevated atmospheric CO2 concentrations decreased denitrifying bacteria numbers,especially at UN and NR conditions(P<0.01).FACE had little impact on the activities of nitrate reductase and nitrite reductase.The study on DP(denitrification potential) showed that DP from FACE plots only arrived to 84.21% and 97.46% of ambients under LN and UN levels.The denitrification was restraind because of their competition between plant growing and microbial activity promoted by FACE.