Variation of Soil Bacterial and Fungal Communities from Fluvo-Aquic Soil Under Chemical Fertilizer Reduction Combined with Organic Materials in North China Plain

Abstract

Since 2015, China has implemented chemical fertilizer reduction, aiming to achieve zero growth in the application rate of chemical fertilizer. Therefore, it is of great significance to explore the effect of chemical fertilizer reduction combined with organic materials in a wheat-maize rotation system from fluvo-aquic soil in North China on soil microbial community. The field experiment included five fertilization treatments, i.e., chemical fertilizer with conventional application rate (F), chemical fertilizer reduction on the basis of conventional fertilization (FR), chemical fertilizer reduction plus straw (FRS), chemical fertilizer reduction combined with organic fertilizer (FRO), and chemical fertilizer reduction combined with organic fertilizer and straw (FROS). The abundance, composition, diversity, and structure of bacterial and fungal communities among treatments were evaluated using qPCR and Illumina high-throughput sequencing technology. The results showed that the concentrations of soil organic matter (SOM) and total nitrogen (TN) in all treatments with addition of organic materials were much higher than those in treatments applied with only chemical fertilizer. The SOM content in the FRS, FRO, and FROS treatments increased by 23.91%, 37.12%, 26.09%, and the TN content increased by 11.96%, 21.08%, 15.22% in comparison with the F treatment, respectively. The lowest contents of available phosphorus (AP) and nitrate nitrogen (NO3−-N) were observed in FR treatment. The AP content in FRO and FROS treatments were 2.44 times and 2.42 times greater than that in FR treatment, respectively. Compared with F treatment, the organic materials input significantly increased bacterial and fungal abundances. More significant effects on the α-diversity with organic fertilizer were observed in the fungal community compared with the bacterial community. The significant increase of Ascomycota and the decline of Mortierellomycota and Glomeromycota were observed in the combined with organic materials treated soils. The nonmetric multidimensional scaling (NMDS) analysis demonstrated that the bacterial community structure in the F treatment was clearly separated from the other treatments, and the other treatments clustered closely, while with respect to fungal community structure, the FRO and FROS treatments grouped together and were separated from the other three treatments. The redundancy analysis (RDA) results showed that the structure of the bacterial community was significantly correlated with SOM and TN, and the fungal community structure was strongly correlated with AP, SOM, and TN. The chemical fertilizer reduction combined with organic fertilizer and straw can effectively improve soil fertility and nutrient availability, altered the community structure of both bacteria and fungi, but only significantly reduced fungal biodiversity. The influence of chemical fertilizer reduction combined with organic materials on fungi was greater than that on bacteria in fluvo-aquic soil of North China.