LAUSR

Intensified livestock system produced large amount of bio-waste, and improper disposal of livestock manure has led to severe environmental consequences. However, knowledge about the time-dependent changes of manure-derived nitrate and soil bacterial diversity along the soil profiles is limited. Vertical variation of soil bacterial diversity and composition in a manure-amended maize field and adjacent non-manured woodland was investigated using high-throughput sequencing technique in spring and autumn along a 1-m profile depth. The soil is classified as aquic inceptisol with a bulk density of 1.31 g cm−3, and a sandy loam texture. The results showed that significant higher amount of nitrate (up to 172.13 mg kg−1) was detected along the soil profile loaded with cattle manure compared with the adjacent non-manured woodland. Soil δ15N-NO3− composition from maize field fall between + 5 and 25‰, while those from woodland fall between − 5 and 15‰. No significant difference in bacterial richness between the two land uses was found, while clear separation of bacterial structure was detected even to the deep soil layers. Canonical correspondence analysis showed that soil organic matter, C/N ratio, nitrate content, pH, and moisture were the major factors influencing the variance of bacterial community composition. Bacterial networks in the maize field harbor more modules than those in the adjacent woodland. Negative standardized effect size measure of mean nearest taxon distance in the soils tended to be more phylogenetically clustered than expected by chance, and was more likely to be clustered along the depth. These findings suggested that soil bacterial β diversity was strongly affected by multi-nutrient properties in terms of high livestock manure load, and had important implications for assessing the environmental impacts on belowground biodiversity in sandy loam soils.