Abstract:

The objective of this study was to evaluate the effect of humic acid addition on soil fungal communities in drip irrigated maize （Zea mays） fields in northern Xinjiang under reduced nitrogen fertilizer supply， and to explore the optimal application of nitrogen fertilizer in farmland. In this study， a randomized block experiment was adopted， and six treatments were set up： No nitrogen fertilizer （CK， 0 kg·ha^-1）， conventional nitrogen fertilizer （T₁， 300 kg·ha^-1）， humic acid application alone （T₂， 90 kg·ha^-1）， conventional nitrogen fertilizer combined with humic acid （T₃）， nitrogen fertilizer reduction of 15% combined with humic acid （T₄）， and nitrogen fertilizer reduction of 30% with humic acid （T₅）. Illumina MiSeq high-throughput sequencing technology was used to analyze the changes in fungal diversity and community structure under the six different treatments， and to explore the effects of nitrogen fertilizer reduction combined with humic acid application on soil fungal community composition. Supporting data on soil nutrient levels and maize yield were also collected. It was found that the soil electrical conductivity （EC） of T₄ and T₅ was significantly reduced by 18.35% and 24.85%， respectively， compared with T₁， and the soil alkaline hydrolyzable nitrogen content was significantly increased by 32.00% and 18.40%， respectively under the same treatments. The maize yield was highest （18038.75 kg·ha^-1） in the T₄ treatment； however， the treatments had no significant effects on the soil fungal community Alpha and Beta diversity. With respect to soil fungi， the relative abundance of Ascomycota under T₄ and T₅ was significantly increased by 21.85% and 24.59%， respectively， compared with T₂， but the relative abundance of Mortierellomycota and Chytridiomycota was significantly reduced. Pearson correlation analysis showed that soil conductivity was significantly positively correlated with Ascobolus and negatively correlated with Botryotrichum， while soil organic matter was negatively correlated with Fusarium presence， and soil alkaline hydrolyzable nitrogen was significantly positively correlated with Cladosporum presence. Further redundancy analysis showed that soil available phosphorus was the main environmental factor affecting the community structure of fungi in this drip irrigated maize field， while soil EC value and alkali hydrolyzable nitrogen were the main environmental factors affecting the horizontal community structure of soil fungi. In conclusion， nitrogen fertilizer reduction combined with humic acid changed the soil fungal community structure， promoted the growth of beneficial bacteria， and inhibited the reproduction of pathogenic fungi by causing changes in soil nutrient content. This information is of great significance for improving the soil microbial environment， maintaining the balance of the soil microbial community and increasing crop yield.

Key words: corn, nitrogenous fertilizer, humic acid, fungal communities, soil nutrients