Effect of straw application time on soil properties and microbial community in the Northeast China Plain

The straw generated from crops significantly affects the soil microbial community when returned to the soil. However, the effects of different application times of straw return treatment on the microbial community remain unknown. Soil samples were collected from different depths (0–30 cm) at different straw return times (every year return (E0y), every 2 years (E1y), and every 3 years (E2y) besides from unfertilized soil (CK) in Fuxin Mongol Autonomous County, Liaoning, China. Soil physicochemical properties analysis and high-throughput sequencing technique were performed to analyze the structure and composition of the soil microbial communities. In deep layer soil, straw return significantly increased the soil water content, field capacity, and porosity and decreased soil bulk density. However, an increase in the soil porosity was not evident when the straw return was applied for consecutive years. When the straw return was applied every 3 years, it significantly increased the alkali-hydrolyzed nitrogen, available phosphorus, and available potassium levels in the deep layer of the soil, but it decreased the soil organic matter levels. Bacterial and fungi community diversity varied between straw return treatments and soil depths. Variations in the relative abundance of some trace microbes (Nitrospirae, Parcubacteria, Acidobacteria, Cercozoa, Rozellomycota, Blastocladiomycota) in different layer soil confirmed the different effects of straw application time on microbial community structure. Straw return treatment applied every 2 or 3 years significantly improved soil structure, increased soil nutrient decomposition, and affected microbial community composition in brown loam soil.