Effects of fertilization on soil microbial community diversity in Chinese arable black soils: research progress and prospects

Black soil of Northeast China is a precious soil resource. Due to long-term overuse without proper maintenance of its fertility, the degradation of arable black soils has been an indisputable issue. Fertilization is an important agronomic practice to maintain/improve the productivity of black soils and ensure crop yield. In this paper, the recent research progress on the influences of long-term application of organic fertilizer, inorganic fertilizer, combined application of organic and inorganic fertilizer, as well as the effects of inorganic fertilizer N, P, K and their combinations on microbial quantity, community alpha diversity and beta diversity of soil bacteria, fungi, diazotrophs and denitrifying bacteria in arable black soils were reviewed. We found that the various findings depend on the location of the experimental sites, the treatments, the types of targeted microorganisms, and even the sampling year. Most studies found that long-term application of chemical fertilizer, especially nitrogen fertilizer, significantly reduces bacterial abundance and alpha diversity index, but has no significant effect on fungal abundance and alpha diversity. Different fertilizations significantly change the microbial beta diversity in black soils, but this change is limited, and the same fertilization treatment does not drive the homogenous succession of soil microbial community structures across different sites, indicating that the distribution of microorganisms in black soils has strong regionalism. In the study of long-term application of different inorganic fertilizers, it was found that N is the most important nutrient driving the change of soil microbial community in arable black soils than P and K. In this paper, besides discussing the changes of soil microbial community structure caused by long-term application of organic fertilizer, the potential ecological risk of antibiotic resistance gene pollution caused by organic fertilizer application and the counter measures of resistance genes are also discussed. Finally, some problems and knowledge gaps regarding the effect of fertilization on microorganisms in arable black soils are summarized, and the five future research comments are proposed.