小麦蚕豆间作对根际土壤氮转化微生物的影响

通过田间小区试验，采用磷脂脂肪酸（PLFA）、实时荧光定量PCR研究了小麦蚕豆间作不同生育期对根际土壤微生物群落的变化、氨氧化细菌（AOB）、氨氧化古菌（AOA）以及反硝化细菌中亚硝酸还原酶（nirK）、一氧化氮还原酶（norB）和氧化亚氮还原酶（nosZ）基因拷贝数以及土壤酶活性和土壤硝态氮、铵态氮含量的影响。结果表明：与单作相比，小麦蚕豆间作显著提高了根际土壤中总的PLFAs生物量、细菌、真菌、放线菌和好氧菌的生物量。土壤样品中的amoA基因拷贝数在10⁵～10⁶范围内AOB的amoA基因数量高于AOA。在不同的生育期，根际土壤中nirK的基因拷贝数都是间作高于单作；在拔节期，间作蚕豆的norB基因显著高于其他种植模式（P<0.05）；在拔节期、抽穗期，nosZ基因均是间作显著高于单作（P<0.05），并随着生育期呈现降低的趋势。间作降低了根际土壤NO₃^--N的含量，提高了NH₄⁺-N的含量（P<0.05）。说明小麦蚕豆间作后改变了根际土壤的微环境，使得土壤微生物群落结构发生改变，这种改变在一定程度上能够对土壤氮素的有效保蓄和供应、同时防止氮素损失和污染起到积极作用，为间作增产提供了氮素营养保障。

Effects of Wheat and Faba Bean Intercropping on Microorganism Involved in Nitrogen Transformation in the Rhizosphere Soils

Soil microorganism is one of the key factors that affects soil ecological activity. It is an important symbol of soil health, and the soil nitrogen cycle is closely related to the microorganisms. The relationship between nitrogen and microorganisms under the intercropping is im-portant for the farmland ecosystem. In this paper, phospholipid fatty acids(PLFA) analysis was used to determine soil microbial communi-ties, e.g., biomasses of anaerobic bacteria, aerobic bacteria, bacteria, fungi and actinobacteria. The abundance of nitrifying genes(AOB, AOA) and three denitrifying genes (nirK, norB, nosZ) were measured using real-time quantitative polymerase chain reaction. The enzymes, nitrate and ammonium concentrations were measured using conventional methods. The results showed that along with the growth period, the TPLFAs(total phospholipid fatty acids) increased and the bacterias, fungus, actinomyces and aerobic bacterias significantly(P<0.05) dif-fered between intercropping and monoculture. The greater abundance of AOB than AOA and the variation range of 10⁵~10⁶ were observed in all samples. The gene copies of norB and nosZ were pronounced by intercropping in the rhizosphere of faba bean at elongation and heading stages, respectively. The abundance of nirK remarkably(P<0.05)differed between intercropping and monoculture. In intercropping rhizo-sphere, the contents of NO₃^--N were lower than monoculture, while the NH₄⁺-N contents were converse (P<0.05). Conclusively, wheat and fa-ba bean intercropping system could change rhizosphere microenvironment, and then the microbial community structure in the soils, which would facilitate the conservation and supplying of soil nitrogen and reduce the nitrogen loss and pollution under the intercropping conditions to some extent. This might be the nitrogen nutrition mechanism for the overyielding of wheat and faba bean intercropping system.