不同氮水平下间作对玉米土壤硝化势和氨氧化微生物数量的影响

利用荧光定量PCR(real-time quantitative PCR,Q-PCR)技术,结合氨氧化细菌(ammonia oxidizing bacteria,AOB)和氨氧化古菌(ammonia oxidizing archaea,AOA)丰度和土壤理化性质的测定,探索了不同氮水平下间作对玉米土壤硝化势(PNF)的影响.试验设置玉米单作和与马铃薯间作两个种植模式,4个施氮水平(不施氮N0、1/2常规施氮N1、常规施氮N2和3/2常规施氮N3)的随机区组试验.结果表明,从不施氮到常规施氮,土壤硝化势和AOA、AOB数量均随施氮量增加而逐渐增加,而高氮(N3)时与N2没有显著差异;间作对土壤硝化势、AOA与AOB数量的影响与施氮量和作物生育期有关,低氮投入(N1)间作有利于增加土壤氨氧化微生物数量和硝化作用.施肥是硝化势增加的主要驱动因子,相关性分析结果表明,土壤含水量是影响PNF的主要环境因子;PNF与土壤中AOA、AOB amoA基因丰度成显著的正相关.尽管玉米马铃薯间作降低了土壤中AOA、AOB amoA基因丰度,却使得间作土壤中AOB占据氨氧化微生物数量上的优势.以上结果表明,施氮和间作均影响了土壤硝化作用和氨氧化微生物AOA和AOB数量的变化,这些变化会影响土壤环境质量.

Effect of Different Nitrogen Rates on the Nitrification Potential and Abundance of Ammonia-oxidizer in Intercropping Maize Soils

The objectives of this study were to explore the effects of different nitrogen rates on the nitrification potential in intercropping maize soils. The experiment included two plantation types (maize monocropping and intercropping maize and potato) and four nitrogen levels (N0: no fertilizer treatment, N1: 1/2 conventional fertilizer treatment, N2: conventional fertilizer treatment, N3: 3/2 conventional fertilizer treatment). Abundance of AOA and AOB was analyzed with real-time quantitative PCR (Q-PCR) and soil properties were also measured. Results of this study suggested that the PNF of soils, the abundance of AOA and AOB were increased with increasing N fertilization in conventional fertilizer range, and there was no significant difference between N2 and N3 treatments. The influences of intercropping on PNF, AOA and AOB were associated with N application rates and crop growth period, as well as the benefits of ammonia oxidizer and nitrification of intercropping on N1 level. Fertilization was obviously the main driving force of the PNF, correlation analysis indicated that water content was the main environmental factor affecting the nitrification potential. Nitrification potential in maize and potato intercropping soils exhibited significant positive correlations with AOA and AOB amoA gene abundance. Maize and potato intercropping could decrease the abundance of AOA and AOB, but it resulted in dominance of AOB among nitrification bacteria in these soils. In conclusion, N fertilizer and intercropping could affect both soil nitrogen internal cycling process and the abundance of AOA and AOB, which further affected soil environmental quality.