This study employed metagenomic sequencing technology to investigate the effects of nitrogen application rates on the composition and structure of soil microbial communities in ‘Korla’ pear orchards, providing scientific evidence for rational fertilization and the sustainable development of pear orchards. The 0–20 cm soil samples from a 6–7-year-old ‘Korla fragrant pear’ orchard were used as the research material to study the changes in the composition and structure of soil microbial communities during the fruit expansion period under four nitrogen application levels: 0, 150, 300, and 450 kg N · hm−2 (denoted as N0, N1, N2, N3, respectively). In combination with an analysis of the soil’s physicochemical properties, the key soil environmental factors driving the changes in bacterial and fungal communities under different fertilization treatments were investigated. In all soil fertilization treatments, the dominant bacterial phyla were Proteobacteria, Actinobacteria, Firmicutes, and Chloroflexi, while the dominant fungal phyla were Ascomycota, Mortierellomycota, and Basidiomycota. Nitrogen application reduced the relative abundance of Actinobacteria and Basidiomycota, with Actinobacteria showing a highly significant negative correlation with total nitrogen (TN, P < 0.01), and Basidiomycota showing a highly significant negative correlation with TN and organic carbon (P < 0.01). At the same time, nitrogen application increased the relative abundance of Firmicutes, Acidobacteria, Gemmatimonadetes, Planctomycetes, and Ascomycota. Regarding bacterial diversity, Pielou’s evenness and Shannon indices were highest under N2 treatment, and the Simpson index showed a highly significant positive correlation with total carbon (TC, P < 0.01), as well as a significant positive correlation with nitrate nitrogen and ammonium nitrogen (P < 0.05). For fungal diversity, Chao1 and Observed Species indices initially increased and then decreased with nitrogen application: N2 > N3 > N1 > N0. Pielou’s evenness, Shannon, and Simpson indices for fungi increased with nitrogen application, showing the order: N2 > N3 > N0 > N1, with the best improvement observed under N2 treatment. Total nitrogen, nitrate nitrogen, ammonium nitrogen, and carbon-to-nitrogen ratio had a highly significant impact on bacterial communities at the phylum level (P < 0.01). Soil alkaline hydrolyzable nitrogen, inorganic carbon, and TC had a significant impact on bacterial communities at the phylum level (P < 0.05). Organic carbon had a highly significant impact on fungal communities at the phylum level (P < 0.01), while pH and TC had a significant impact on fungal communities at the phylum level (P < 0.05). The application of nitrogen fertilizer alters the physical and chemical properties of the soil, subsequently changing the composition and structure of soil bacterial and fungal communities. Therefore, in the cultivation of ‘Korla fragrant pear,’ the supply of nitrogen should be appropriately controlled. For 6–7-year-old ‘Korla fragrant pear,’ a recommended fertilization model with a nitrogen application rate of 300 kg·hm−2 is suggested, as it can result in a more diverse microbial community structure.

Study on the Response of Soil Microbial Communities to Different Nitrogen Application Rates in ‘Korla Fragrant Pear’ Orchards

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发表日期：

2025年9月15日

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Zeyue Ma,
Xuemei Wang,
Lei Feng,
Wei Li,
Zhan Huang,
Minghao Sun,
Xing Shen,
Zhongping Chai

摘要

This study employed metagenomic sequencing technology to investigate the effects of nitrogen application rates on the composition and structure of soil microbial communities in ‘Korla’ pear orchards, providing scientific evidence for rational fertilization and the sustainable development of pear orchards. The 0–20 cm soil samples from a 6–7-year-old ‘Korla fragrant pear’ orchard were used as the research material to study the changes in the composition and structure of soil microbial communities during the fruit expansion period under four nitrogen application levels: 0, 150, 300, and 450 kg N · hm⁻² (denoted as N₀, N₁, N₂, N₃, respectively). In combination with an analysis of the soil’s physicochemical properties, the key soil environmental factors driving the changes in bacterial and fungal communities under different fertilization treatments were investigated. In all soil fertilization treatments, the dominant bacterial phyla were Proteobacteria, Actinobacteria, Firmicutes, and Chloroflexi, while the dominant fungal phyla were Ascomycota, Mortierellomycota, and Basidiomycota. Nitrogen application reduced the relative abundance of Actinobacteria and Basidiomycota, with Actinobacteria showing a highly significant negative correlation with total nitrogen (TN, P < 0.01), and Basidiomycota showing a highly significant negative correlation with TN and organic carbon (P < 0.01). At the same time, nitrogen application increased the relative abundance of Firmicutes, Acidobacteria, Gemmatimonadetes, Planctomycetes, and Ascomycota. Regarding bacterial diversity, Pielou’s evenness and Shannon indices were highest under N₂ treatment, and the Simpson index showed a highly significant positive correlation with total carbon (TC, P < 0.01), as well as a significant positive correlation with nitrate nitrogen and ammonium nitrogen (P < 0.05). For fungal diversity, Chao1 and Observed Species indices initially increased and then decreased with nitrogen application: N₂ > N₃ > N₁ > N₀. Pielou’s evenness, Shannon, and Simpson indices for fungi increased with nitrogen application, showing the order: N₂ > N₃ > N₀ > N₁, with the best improvement observed under N₂ treatment. Total nitrogen, nitrate nitrogen, ammonium nitrogen, and carbon-to-nitrogen ratio had a highly significant impact on bacterial communities at the phylum level (P < 0.01). Soil alkaline hydrolyzable nitrogen, inorganic carbon, and TC had a significant impact on bacterial communities at the phylum level (P < 0.05). Organic carbon had a highly significant impact on fungal communities at the phylum level (P < 0.01), while pH and TC had a significant impact on fungal communities at the phylum level (P < 0.05). The application of nitrogen fertilizer alters the physical and chemical properties of the soil, subsequently changing the composition and structure of soil bacterial and fungal communities. Therefore, in the cultivation of ‘Korla fragrant pear,’ the supply of nitrogen should be appropriately controlled. For 6–7-year-old ‘Korla fragrant pear,’ a recommended fertilization model with a nitrogen application rate of 300 kg·hm⁻² is suggested, as it can result in a more diverse microbial community structure.