Impact of nitrogen fertilizer application on soil fungal diversity and maize yield variation in Shandong Province, China

Maize is one of the major crops cultivated in northern Shandong Province and contributes significantly to China's maize production, and nitrogen (N) application to the soil can have a marked impact on maize yield and soil microbial productivity. The current environmental challenge, which needs urgently to be addressed, is to effectively utilize fertilizer nitrogen to improve crop production without causing environmental stress in sustainable agroecosystems. Soil fungi can improve plant health and crop performance through improved nutrient uptake and reducing plant stress levels. How soil N influences fungal diversity and maize yield at spatial patterns remains unclear. In this study, the influences of different soil N treatments on maize yields and fungal diversity were investigated in maize fields at five N rates (from 0 to 120 kg ha−1). High-throughput sequencing of the internal transcribed spacer (ITS) region revealed that α- and β-diversities of fungi significantly increased at 80 kg N ha−1 (N80) but decreased significantly in the control (N0) and other N treatments. Variations in the NC model predicted strong fungal distribution patterns (R2 = 0.60) among all the treatments. The highest proportion of operational taxonomic units (OTUs) (68.99%) was observed at N80. The study also found that the complexity of the co-occurrence network significantly stabilized at N80, but a decrease in network complexity was observed at N120. The study showed that, relative to the control, the addition of N to the soil significantly increased the abundance of Ascomycota at the phylum level and Chaetomium, Fusarium, and Mortierella at the genus levels, with average abundances of 5.82%, 1.67%, and 19.58%, respectively. Functional ecology analysis indicated that soil N upregulated the composition of ecological fungal communities by stochastic processes. The composition of major fungal sub-communities was positively correlated with nitrogen/carbon cycling at N80. Moreover, results also indicated that the yields (3.14 t ha−1) and other agronomic effects at N80 were significantly higher than those in the other treatments. This study demonstrates that optimal nitrogen application achieves increases in both fungal diversity and yield, contributing to improved crop production and sustainability at spatial scales.