生物活性抑制剂对淹水稻田痕量气体排放的影响及其机理

With no wheat straw powder amended all treatments with inhibitors had much lower methane emission during rice growth than the treatment with urea alone (control), which was contrary to methane emission from the cut rice-soil system. Especially for treatments with dicyandiamide DCD and with DCD plus hydroquinone HQ, the total amount of methane emission from the soil system and intact rice-soil system was 68.25-46.64% and 46.89-41.78% of the control, respectively. Hence, DCD, especially in combination with HQ, not only increased methane oxidation in the floodwater-soil interface following application of urea, but also significantly enhanced methane oxidation in rice root rhizosphere, particularly from its tillering to booting stage. Wheat straw powder incorporated into flooded surface layer soil significantly weakened the above-mentioned stimulating effects. Regression analysis indicated that methane emission from the rice field ecosystem was related to the turnover of ammonium-N in flooded surface layer soil. A significantly nonlinear negative relation was found between the N2O emission and the CH4 emission when no wheat straw was added, but it was hard to quantify this trade-off relation when wheat straw was incorporated into the flooded surface layer soil. The mineral N content in the floodwater can to some extent predict the emissions of N2O and CH4 in rice production.With no wheat straw amendment, all treatments with inhibitors, especially with HQ + DCD, had a much smaller N2O emission during the rice growing period than the urea treatment, whereas a substantially increased N2O emission was observed from a rice-free soil with inhibitors. The N2O emission from the rice-planted soil was exponentially positive correlated with the NO3--N concentration in the rice aboveground biomass. Stepwise regression analysis indicates that denitrification in the flooded surface layer soil was the main source of N2O emission from this wetland rice cultivation, particularly when wheat straw was added. By comparing the total N2O emission from the rice-free soil and from the rice-planted soil, we found that urea application alone might induce an apparent plant-mediated N2O emission, being 0.39 ± 0.08% of the applied urea N. Wheat straw incorporated into the flooded surface layer soil could increase the plant-mediated N2O emission significantly. However, application of HQ + DCD could reduce this emission (0.27 ± 0.08% of the applied urea N, compared with 0.89 ± 0.18% in the urea treatment). NO3--N in young rice plants can substantially contribute to the plant-mediated N2O flux..During the whole period of wheat growth, HQ+DCD induced an increasing 15N uptake by plant, and even promoted the translocation of absorbed 15N from stem to grain. In the presence of inhibitors, organic plus chemically fixed 15N occupied a large portion of soil 15N recovery at maturity stage of wheat growth (34.3-50.6%, in contrast to 9.9% in the absence of inhibitors), and DCD and DCD+HQ could remarkably reduce the remaining soil (NO3- +NO2-)-15N. DCD and DCD+HQ retarded N2O flux from the soil-wheat system after treatment with urea and reduced the total N2O flux during the whole period of wheat growth. Treatment with both inhibitors had much lower gaseous N losses than that with HQ or DCD alone. Hence, a proper combination application of HQ and DCD is an efficient way to improve urea-N efficiency, while decreasing its loss to the environment. When excessively available N can be avoided in rice-wheat rotation fields, an effective method for mitigation of both N2O and CH4 emissions from arable soils is the use of N fertilizers together with inhibitors and the control of irrigation water that can lead to small emissions. However, much further field experiments are necessary before the method is assessed

采用模拟淹水稻田盆栽实验、田间野外观测和室内培养相结合的方法，研究相关生物活性抑制剂氢醌与双氢胺及二者组合对淹水稻田中甲烷和氧化亚氮净排放量的影响并分析其机理。阐明在水稻不同生育期内水稻根际和剖面不同层次土壤中氧化亚氮和甲烷形成与消耗的规律及抑制剂影响，为提高淹水稻田尿素肥效又阻控氧化亚氮和甲烷排放量提供科学理论依据。.