Nitrogen (N) fertilization in agroecosystems can alter soil physicochemical and biological properties. Yet, little is known about the relative importance of short- and long-term effects of N inputs on soil microbial communities. In a continuous corn (Zea mays L.) trial from southern Ontario, Canada, we analyzed the response of soil microbial community structure to contrasting mineral N fertilization rates applied either continuously for 10 years (low: 30, mid: 87, high: 218 kg N ha⁻¹ y⁻¹) or ‘shocked’ with a higher/lower N rate once every five years. Soil samples (0–15 cm) were collected on the last year of trial at corn early reproductive stage. Microbial biomass was analyzed using fatty acid methyl esters and microbial diversity and community composition using high-throughput sequencing. The effects of N inputs on soil microbial community structure were minor, mostly in the long-term, and slightly different between prokaryotes and fungi. The total N input over 10 years (long-term) was correlated positively with bacterial biomass and negatively with fungal richness. Total N inputs also caused minor shifts in microbial community composition. Shock N rates (short-term) did not affect microbial community structure except for the relative abundance of some taxa. Taxonomic changes were observed at lower levels (i.e., genus), with no clear changes at the phylum level, and low N generally favoured more phylogenetically diverse taxa than high N. Overall, our results suggest that, even under the uniform conditions of corn monoculture, soil microbial communities can be shaped by N fertilization rates commonly used in agriculture. Depending on the functional traits of the sensitive organisms, such structural changes could lead to changes in nutrient cycling dynamics and crop growth.

农业生态系统中的氮 (N) 施肥可以改变土壤的理化和生物特性。然而，关于氮输入对土壤微生物群落的短期和长期影响的相对重要性知之甚少。在加拿大安大略省南部的连续玉米 ( Zea mays L.) 试验中，我们分析了土壤微生物群落结构对连续 10 年（低：30，中：87，高：218）的对比矿物氮肥施用率的响应公斤 N ha ^-1 y ^-1) 或“震惊”每五年一次更高/更低的 N 率。在玉米早期生殖阶段的最后一年试验中收集土壤样品（0-15 厘米）。使用脂肪酸甲酯分析微生物生物量，使用高通量测序分析微生物多样性和群落组成。N输入对土壤微生物群落结构的影响较小，主要是长期的，原核生物和真菌之间略有不同。10 年（长期）的总氮输入与细菌生物量呈正相关，与真菌丰富度呈负相关。总氮输入也引起微生物群落组成的微小变化。除了某些分类群的相对丰度外，冲击 N 率（短期）不影响微生物群落结构。在较低水平（即属）观察到分类学变化，在门水平没有明显变化，低氮通常比高氮更倾向于系统发育多样化的分类群。 总的来说，我们的结果表明，即使在玉米单一栽培的统一条件下，土壤微生物群落也可以通过常用的施氮率来塑造在农业方面。根据敏感生物的功能特性，这种结构变化可能导致养分循环动态和作物生长的变化。