The use of nitrogen fertilizer on bioenergy crops such as switchgrass results in increased costs, nitrogen leaching and emissions of N₂O, a potent greenhouse gas. Intercropping with nitrogen-fixing alfalfa has been proposed as an environmentally sustainable alternative, but the effects of synthetic fertilizer versus intercropping on soil microbial community functionality remain uncharacterized. We analysed 24 metagenomes from the upper soil layer of agricultural fields from Prosser, WA over two growing seasons and representing three agricultural practices: unfertilized switchgrass (control), fertilized switchgrass and switchgrass intercropped with alfalfa. The synthetic fertilization and intercropping did not result in major shifts of microbial community taxonomic and functional composition compared with the control plots, but a few significant changes were noted. Most notably, mycorrhizal fungi, ammonia-oxidizing archaea and bacteria increased in abundance with intercropping and fertilization. However, only betaproteobacterial ammonia-oxidizing bacteria abundance in fertilized plots significantly correlated to N₂O emission and companion qPCR data. Collectively, a short period of intercropping elicits minor but significant changes in the soil microbial community toward nitrogen preservation and that intercropping may be a viable alternative to synthetic fertilization.

中文翻译：

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苜蓿-柳枝稷间作对微生物群落结构和功能的影响

在柳枝稷等生物能源作物上使用氮肥会导致成本增加、氮浸出和 N _2排放O，一种强效温室气体。已提出与固氮苜蓿间作作为环境可持续的替代方案，但合成肥料与间作对土壤微生物群落功能的影响仍未确定。我们在两个生长季节分析了来自华盛顿州普罗瑟农田上层土壤层的 24 个宏基因组，代表了三种农业实践：未施肥柳枝稷（对照）、施肥柳枝稷和柳枝稷与苜蓿间作。与对照地块相比，合成施肥和间作并未导致微生物群落分类和功能组成发生重大变化，但注意到了一些显着变化。最值得注意的是，菌根真菌，随着间作和施肥，氨氧化古菌和细菌大量增加。然而，只有受精地块中的 β-变形菌氨氧化细菌丰度与 N 显着相关。₂ O 排放和伴随的 qPCR 数据。总的来说，短时期的间作引起土壤微生物群落向氮保存方向发生微小但显着的变化，间作可能是合成施肥的可行替代方案。