Objectives This study explored the effects of organic materials on nutrient accumulation in maize, to provide nutrient management techniques for maintaining soil microbial ecosystems and sustainable agricultural development.

Methods A positioning field experiment was carried out in Heilongjiang Province for two consecutive years. The experiment included a chemical fertilizer control (CK) and three chemical fertilizer combined with organic material treatments (maize straw decomposed, fulvic acid, and chicken manure). During the maize harvest period, the study investigated the accumulation of nutrients in the upper part of the maize field, the activity of soil enzymes, and the microbial diversity of soil bacteria and fungi.

Results Compared with CK, combined organic material application increased the yield and accumulation of nitrogen and phosphorus in maize plant. The maize straw decomposed treatment resulted in significantly different bacteria and fungal community structures, compared to the other treatments. In all the treatment soils, the number of differential microbial species specific to bacteria was higher than that to fungi. The four bacterial phyla with a relative abundance greater than 5% were Proteobacteria, Acidobacteriota, Gemmatimonadota and Actinobacteriota. Three bacterial families are Sphingomonadaceae, Gemmatimonadaceae and Vicinamibacteraceae, and one bacterial genus was Sphingomonas. The three fungal phyla with a relative abundance of more than 5% were Ascomycota, Basidiomycota and Mortierellomycota, and one fungal family was Chaetomiaceae. One fungal genus was Podospora. All the organic material treatments, except for the treatments involving fulvic acid on sucrase activity and maize straw decomposed, as well as fulvic acid on catalase activity, did not significantly change the activities of soil enzymes. The relative abundance of Basidiomycota was negatively correlated with maize nitrogen and potassium accumulation, and the relative abundance of Mortierellomycota was positively correlated with maize potassium accumulation.

Conclusions At the base of conventional chemical fertilizer application, the combined use of organic materials could further enhance the accumulation of nitrogen, phosphorus, as well as the yield of maize. The application of maize straw decomposed leads to significantly different bacterial and fungal community structures. The application of chicken manure and maize straw decomposed increases the number of differential bacterial species, but decreases the number of differential fungal species, while fulvic acid does not have an impact on them. Enzyme activities show a close correlation with soil microbial composition, especially with Sphingomonas in the bacterial phylum and Podospora in the fungal phylum. Maize nitrogen and phosphorus uptake are correlated with soil sucrase activity.