关键词: 氮肥, 丛枝菌根真菌, 玉米, 土壤氧化亚氮排放通量, 土壤细菌

Abstract:

【Objective】 The aim of this study was to understand the mechanism of arbuscular mycorrhizal fungi (AMF) on soil nitrous oxide (N₂O) emissions, so as to provide the theoretical basis for increasing maize yield, improving nitrogen (N) use efficiency and reducing greenhouse gas emissions. 【Method】 A 2-factorial greenhouse experiment was established during maize growth periods in 2016 and 2017. The factors were as follows: (1) N fertilizer rates (180 kg N·hm^-2 (N1) and 360 kg N·hm^-2 (N2)), and (2) three mycorrhizae treatments, including a control (M0, neither roots nor AMF could enter the hyphal chamber from the growth chamber), an AMF treatment (M1, only AMF can enter the hyphal chamber from the growth chamber), and a root treatment (M2, both roots and AMF can enter the hyphal chamber from the growth chamber). Maize grain yield, plant biomass and their N accumulation, and soil N₂O flux were measured. Soil bacterial community structure and diversity at maize maturity stage was determined by using the high throughput sequencing technique on Hiseq 2500 PE250. 【Result】 Both N fertilizer rates and mycorrhizae treatments significantly affected maize yield, plant N accumulation and soil N₂O flux. Compared with M0, maize yield under M1 and M2 under the conditions of N1 input increased by 38% and 82%, by 30% and 52% for aboveground N accumulation, respectively, and reduced by 26% and 65% for soil inorganic N, respectively. However, under the conditions of N2 input, the maize yield under M1 and M2 increased by 16% and 48%, by 9% and 33% for aboveground N accumulation, and reduced by 34% and 55% for soil inorganic N, respectively. Compared with the M0, the total N₂O emission of M1 and M2 treatments reduced by 17% and 40% under the conditions of N1 input, and by 41% and 67% for the N₂O emission intensity, respectively; while under the conditions of N2 input, the total N₂O emission reduced by 26% and 45%, and by 28% and 57% for the N₂O emission intensity, respectively. Nonmetric multidimensional scaling analysis showed that both N fertilizer rates and mycorrhizae treatments had significant effects on bacterial communities’ composition. Compared with N1, the relative abundance of Proteobacteria and Gemmatimonadetes under N2 treatment on phyla level reduced by 6% and 15%, increased by 32% for Actinobacteria, while on genera level, the Streptomyces increased by 27%, and reduced by 8% for Gemmatimonas. Compared with M0 under the conditions of N1 input, the relative abundance of Streptomyces under M1 and M2 increased by 64% and 205%, by 31% and 53% for Gemmatimonas; however, under the conditions of N2 input, the relative abundance of Streptomyces under M1 and M2 increased by 10% and 93%, respectively, the Gemmatimonas for M1 reduced by 2%, and increased by 56% for M2. Moreover, the relative abundance of soil Streptomyces and Gemmatimonas was negatively related with soil N₂O emission, but positively related with maize yield. 【Conclusion】 Arbuscular mycorrhizal fungi could reduce soil N₂O emission under both higher and lower N fertilizer application rate by increasing the maize N uptake, and regulating the bacterial composition, especially increasing the relative abundance of Streptomyces and Gemmatimonas.

Key words: nitrogen fertilizer, arbuscular mycorrhizal fungi, maize, soil N₂O flux, soil bacteria