Structure of soil fungal communities under long-term inorganic and organic fertilization in black soil of Northeast China

Objectives The abundance, diversity and composition of fungal community were identified, and the main relationship between soil fungi community variation and soil fertilizer would be revealed in this paper. Methods Based on 36-years' fertilization experiment in Heilongjiang Academy of Agricultural Sciences, four treatments were selected to study:no fertilizer (CK); manure (M); chemical N, P and K fertilizer (NPK); and manure with NPK(MNPK). The ITS gene was applied as target gene, using Illumina Miseq sequencing and quantitative PCR method. The fungal abundance, diversity and composition in black soil were analyzed. The relationship of fertilization and fungi community was calculated. Results Long term application of chemical fertilizers reduced soil pH and led to soil acidification, while manure did not show same impact. ITS gene abundance in ratio in MNPK (26.91104) was significantly higher than that in NPK, and the ratio was in order of MNPK M CK NPK. NPK treatment was more than in MNPK. Bacteria-to-fungi ratio was positively correlated with soil pH. Alpha diversity of fungi community of MNPK was slightly greater than that of NPK. Ascomycota and Zygomycota were the top two majority fungi found in black soil. The relative abundance of the fungi community was significantly different among the four fertilization treatments. The relative abundanceof Ascomycota in CK was 45.35%, in MNPK and NPK were 50.93% and 56.16%, respectively. Manure reduced the relative abundance of pathogenic fungi. The relative abundances of highly aggressive Cochliobolus in MNPK (0.41%) and M (0.39%) were significantly lower than those of CK (3.25%) and NPK (2.08%). Canonical correlation analysis indicated that the selected soil properties could explain 73.3% of the variation, and fungal communities were closely positively correlated with soil available P (Contribution=32.4%, P=0.002), NH4+-N concentration (Contribution=14.8, P=0.01) and NO3--N concentration (Contribution=16.2%, P=0.048).Conclusions Long-term fertilization affects fungal abundance, diversity and community characteristics of black soil. Compared with chemical fertilizers, manure alone and manure combined with chemical NPK fertilizers will improve the fungal communities structures, decrease fungal abundance and increase diversity activity, enhance the soil pH, slowed down soil acidification. Among the soil fertility factors, the soil available P, NH4+-N and NO3--N concentrations are the three dominant factors determining the variation of fungal communities structures.