Nitrosospira Cluster 8a Plays a Predominant Role in the Nitrification Process of a Subtropical Ultisol under Long-Term Inorganic and Organic Fertilization

Abstract

Long-term effects of inorganic and organic fertilization on nitrification activity (NA) and the abundances and community structures of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) were investigated in an acidic Ultisol. Seven treatments applied annually for 27 years comprised no fertilization (control), inorganic NPK fertilizer (N), inorganic NPK fertilizer plus lime (CaCO) (NL), inorganic NPK fertilizer plus peanut straw (NPS), inorganic NPK fertilizer plus rice straw (NRS), inorganic NPK fertilizer plus radish (NR), and inorganic NPK fertilizer plus pig manure (NPM). In nonfertilized soil, the abundance of AOA was 1 order of magnitude higher than that of AOB. Fertilization reduced the abundance of AOA but increased that of AOB, especially in the NL treatment. The AOA communities in the control and the N treatments were dominated by the and B1 clades but shifted to clade A in the NL and NPM treatments. cluster 8a was found to be the most dominant AOB in all treatments. NA was primarily regulated by soil properties, especially soil pH, and the interaction with AOB abundance explained up to 73% of the variance in NA. When NL soils with neutral pH were excluded from the analysis, AOB abundance, especially the relative abundance of cluster 8a, was positively associated with NA. In contrast, there was no association between AOA abundance and NA. Overall, our data suggest that cluster 8a of AOB played an important role in the nitrification process in acidic soil following long-term inorganic and organic fertilization. The nitrification process is an important step in the nitrogen (N) cycle, affecting N availability and N losses to the wider environment. Ammonia oxidation, which is the first and rate-limiting step of nitrification, was widely accepted to be mainly regulated by AOA in acidic soils. However, in this study, nitrification activity was correlated with the abundance of AOB rather than that of AOA in acidic Ultisols. cluster 8a, a phylotype of AOB which preferred warm temperatures, and low soil pH played a predominant role in the nitrification process in the test Ultisols. Our results also showed that long-term application of lime or pig manure rather than plant residues altered the community structure of AOA and AOB. Taken together, our findings contribute new knowledge to the understanding of the nitrification process and ammonia oxidizers in subtropical acidic Ultisol under long-term inorganic and organic fertilization.

Effects of Organic Fertilizers on the Soil Microorganisms Responsible for N2O Emissions: A Review

“…However, this phenomenon seems to occur only in soils with low pH and substrate availability. In the soils with inorganic N additions or relatively high pH, AOB is still the main players [ 82 , 83 ], as reported by Lin et al [ 68 ], who observed a shift from AOA to AOB accompanied by an increase in pH of an acidic soil after 44 years of pig manure and inorganic N additions. Microorganisms carrying nirK and nirS denitrifying genes are also sensitive to pH change and, as mentioned earlier, to changes in C availability [ 84 ].…”

“…Ammonia oxidizers are particularly sensitive to the supply of NH 4 + since they are lithoautotrophic microorganisms. Thus, animal manures typically increase the abundance and activity of ammonia oxidizers, leading to overall high nitrification rates [ 56 , 68 ]. While mineralization kinetics of organic N depends on environmental conditions and C:N ratios of the manure, nitrification of NH 4 + proceeds relatively quickly, especially under high temperature and oxygen availability.…”

Dominant Tree Mycorrhizal Associations Affect Soil Nitrogen Transformation Rates Through Mediating Microbial Abundances in a Temperate Forest

“…Dominant OTUs (relative abundance >1%) were taxonomically classi ed through constructing neighbor-joining phylogenetic trees in the MEGA7 software (Kumar et al 2016) using representative sequences of AOA or AOB amoA genes and taxonomically determined reference sequences. Reference sequences for AOA clusters were from Alves et al (2013) and Lin et al (2019), and for AOB clusters were from and . Diversity (Shannon) and richness (Chao1) of AOA and AOB were calculated by the QIIME.…”

Conservation tillage regulates soil bacterial community assemblies, network structures and ecological functions in black soils

“…Burkholderia and Mesorhizobium have been widely reported to have nitrogen xation capabilities (Fan et al, 2019;Soe et al, 2020), and their abundances were signi cantly higher in the rhizosphere soils with NT and RT than in those with MP. OTU2806 (Nitrosospira multiformis) and OTU3942 (Nitrosospira tenuis), which play a pivotal role in the nitri cation process (Lin et al, 2018), were enriched in the bulk soils with RT and rhizosphere soils with NT. OTU4404 (Bradyrhizobium japonicum) and OTU2109 (Rhizobium etli) are widely documented to facilitate nodulation and biological nitrogen xation of legumes (Kalita and Malek, 2020; Rivas et al, 2009; Roper et al, 2020), and they increased in the rhizosphere soils with NT and RT.…”