硝化抑制剂对毛竹林土壤N_2O排放和氨氧化微生物的影响

为了探索硝化抑制剂在毛竹生产中的施用技术,通过培养试验研究3,4-二甲基吡唑磷酸盐(DMPP)和双氰胺(DCD)两种硝化抑制剂对毛竹林施用尿素后土壤N2O排放、氮素转化和相关氨氧化细菌(AOB)、氨氧化古菌(AOA)群落结构和丰度的影响。试验设(1)对照(CK)、(2)单施尿素(Urea)、(3)尿素+1%DMPP(DMPP占总N的1%,下同);(4)尿素+1.5%DMPP;(5)尿素+10%DCD;(6)尿素+15%DCD等6个处理,测定N2O的排放动态以及气体排放转折点时的土壤特征指标。结果表明:与单施尿素相比,160 d的时间内两种DMPP用量处理的土壤N2O累积排放减排幅度均为54%,而10%DCD和15%DCD处理的土壤分别减少28%和41%。DMPP和DCD处理50 d和90 d时土壤的NH4+-N含量均显著高于(p0.05)单施尿素处理,而NO3--N含量和表观硝化率则恰好相反,但两种抑制剂间无差异。DMPP处理的AOB群落结构的变化从10 d开始显现,至50 d和90 d时仍保持明显的抑制状态,而DCD处理则至90 d时抑制作用基本消失。单施尿素AOB功能基因(amo A)的丰度均显著高于硝化抑制剂处理(90 d时尿素+10%DCD处理除外);在整个培养期内,尿素和对照土壤的AOA群落结构相似,硝化抑制剂反而增加了AOA功能基因的丰度,表明硝化抑制剂对AOA丰度无明显抑制作用。即两种硝化抑制剂主要通过抑制AOB起作用;调节土壤p H至中性范围,并在1%DMPP施用条件下,硝化抑制剂的抑制效果最显著。

Effects of Nitrification Inhibitors on Soil N2O Emission and Community Structure and Abundance of Ammonia Oxidation Microorganism in Soil under Extensively Managed Phyllostachys edulis Stands

AbstractObjective]Combined application of nitrification inhibitors and ammonium-containing fertilizers is considered an effective means for improving N utilization efficiency and reducing pollution risk. To determine effects of the use of two nitrification inhibitors:dicyandiamide(DCD)and 3, 4-dimethylpyrazole phosphate(DMPP),separately,on N2O emission,nitrogen transformation rate, and community structure and abundance of ammonia-oxidizing bacteria(AOB)and ammonia-oxidizing archaea(AOA)in soils applied with ammonium-containing fertilizers.Method]An in-lab incubation test was conducted of soil samples collected from an extensively managedPhyllostachys edulis plantation. The soil samples were subjected to six treatments,separately,that is(1)CK(no fertilizer);(2) Urea(Urea);(3)Urea + 1% DMPP(1% of Urea in quantity);(4)Urea + 1.5% DMPP;(5) Urea + 10% DCD;(6)Urea + 15% DCD. Dynamics of N2O emissionand soil parameters at the time of N2O emissionturning point(10 d,50 d and 90 d)were determined.Result]Results show that both of the two nitrification inhibitors greatly reduced N2O emission during the 160 days of incubation. The reduction rate in Treatments Urea + DMPP(both 1% and 1.5%),Treatment Urea +10% DCD,and Treatment Urea +15% DCD was 54%,28%,and 41%,respectively. Significant differences were found in cumulative emission of N2O(p<0.05)between the treatments,but not between the two Urea + DMPP treatments. The treatments in which urea was combined with nitrification inhibitors were similar to Treatment CK in N2O emission rate during the first 40 days of incubation,and then the formers began to rise gradually with the incubation going on and exceeded CK. Significantly lower N2O cumulative emission was observed in Treatment Urea +15% DCD than in Treatment Urea +10% DCD. Soil NH4+-N levels due to urea application increased rapidly to a maximum and then decreased gradually,with Treatment Ureabeing lower than all the urea + inhibitor treatments on D50 and D90 of incubation;NO3--N concentrations exhibited an opposite trend. The DGGE profiles of soil ammonia oxidizing archaea(AOA)and ammonia oxidizing bacteria(AOB)revealed that DCD and DMPP significantly inhibited AOB in abundance. The effect began to be obvious on D10 of incubation and remained to be significant on D50 and D90 in Treatments Urea + MPP,but faded on D90 in Treatments Urea + DCD. Treatment Urea was obviously much higher than all the urea + inhibitor treatments in abundance of AOBamoAexcept for Treatment Urea +10% DCD on D 90 of incubation. In contrast,little effect of the use of inhibitors was detected on AOA community,with AOAamoAcopy number actually increasing in all treatments. In summary,the dynamics of N2O emission,soil NH4+-N content,and abundance of AOBamoA and AOAamoAdid vary synchronously,indicating that N2O emission was controlled by different factors in different time periods for the two bacterial groups. The effect of nitrification inhibitors suppressing AOB led to low N2Oemission during the first 40 days of incubation. Although the soil was sufficient in ammonium content and abundant in AOA,the slightly acidic condition(pH about 6.0)may have limited nitrification activity of the group. During the period of D50-D90 of incubation,Changes in AOA triggered by decrease in soil pH with time may be responsible for the increase inN2O emission because the AOBamoAabundance was still low.Conclusion]In conclusion,nitrification was mainly controlled via inhibition of AOB activity and application of DMPP at a 1% rate appears to be sufficient to reduce nitrification. It is also suggested that adjusting soil pH to nearly neutral may prolong the effect of the inhibitor DMPP.