Varying nitrogen fertilization and soil bacterial community dynamics at three growth phases of winter wheat production

Wheat-rice straws returning with varied nitrogen (N) fertilization rates has become a routine part of winter wheat production in the Jianghan Plain of Yangtze River Basin, Hubei Province, China. The effect of this practice is mostly reported on soil physico-chemical properties and grain yield at the expense of soil bacterial community in this major wheat growing area. Therefore, the present study was aimed to evaluate changes in soil bacterial community diversity under varying straw return (SR) and N fertilization at three stages of winter wheat growth (i.e., before seeding, jointing and maturation stages). The wheat variety, Yangmai 23 under three rates of rice SR (0, 50 and 100%) and four N fertilization rates (0, 33.3, 70 and 100%) with 180 kg/ha urea were employed. Soil physico-chemical properties including pH, total nitrogen, nitrate (NO3−), ammonium (NH4+), total phosphorus, potassium and soil moisture were measured at the three growth stages. A high-throughput sequencing of soil bacterial community was conducted on an Illumina HiSeq PE250 platform, yielding 67,052 operational taxonomic units and with 97% sequence similarity. About 35,941 were successfully classified at least in different levels of soil bacteria taxonomy (i.e., phylum (n = 63), class (n = 203), order (n = 499), family (n = 826), genus (n = 1,712), and species (n = 4,799). The Ace and Chao bacteria community richness, Shannon and Simpson diversity indices varied significantly (p < 0.05) across the three stages. The top five soil bacteria at phylum level consisted of Chloroflexi (27.75%), Actinobacteriota (18.89%), Proteobacteria (13.81%), Acidobacteriota (13.59%), and Firmicutes (25.96%). The relative abundance of Chloroflexi increased from before seeding compared to either jointing or maturation stage. Some of the soil bacteria phyla were significantly associated with soil physio-chemical properties at the three stages. The final grain yield significantly correlated with Chloroflexi, Proteobacteria, Desulfobacterota and WS4 at before seeding; while, Desulfobacterota (r = 0.72) and Sva0485 (r = 0.59) abundance at the jointing stage correlated with grain yield. KEGG functional analysis revealed soil bacteria communities were mainly involved in transport and amino acids metabolism, nucleotides, carbohydrate, coenzymes, lipids, inorganic ions and secondary metabolites, energy production and transformation. These results provide valuable information for potential formulation of sustainable soil management strategies taking into consideration soil bacterial community dynamics.