Influence of drought and dry-wet alternation on nitrogen transformation and low abundance microorganisms in tea garden soil

Aim: The soil water availability seriously limits the growth and development of tea plants, and soil microorganisms are an important medium to regulate soil nutrient cycling. In this study, the effects of water supply mode on soil nitrogen nutrition and soil microbes in tea gardens were investigated. Methodology: This experiment set up consisted two water supply modes (consecutive drought and dry-wet alternation) by using the soil microcosm incubation experiment, and four treatments were set: 20% water holding capacity for 21day (D21); 20% water holding capacity for 1-7 days and 60% water holding capacity for 8-21 days (D7W14); 20% water holding capacity for 1-14 day and 60% water holding capacity for 15-21 days (D14W7); 20% water holding capacity for 1-7 days, 60% water holding capacity for 8-14 days, 20% water holding capacity for 15-21 days (D7W7D7). Destructive sampling was carried out to determine soil NH4+-N, NO3--N, soil enzyme activities. 16S rRNA sequencing technique was used to determine the change in soil microbial diversity. Results: The results showed that the consecutive drought reduced the content of soil NH4+-N to 13.97 mg kg-1, and the net nitrogen mineralization was negative (-2.75 mg kg-1) after 21 days of incubation. Dry-wet alternation promoted the increase in of soil net nitrogen mineralization quantity and net nitrification quantity, which rose to 3.48-26.41 mg kg-1 and 8.07-23.11 mg kg-1, respectively. Different water supply modes had no significant impact on the structure of dominant soil microbial community, and the effect mainly focused on relative abundance, especially dry-wet alternation mode. Compared with the continuous drought treatment, the relative abundance of Nitrospirae, Actinobacteria, Chloroflexi, Patescibacteria, Latescibacteria, Rokubacteria, Acidobacteria were significantly different in different dry-wet alternation treatments, while the relative abundance of Nitrospirae, Acidobacteria, Latescibacteria, Gemmatimonadetes, Patescibacteria and Chloroflexi also increased or decreased significantly among different dry-wet alternation treatments. Among the physical and chemical factors of tea garden soil, NO3- had the most significant effect on the structure of microbial community. Interpretation: Different water supply can significantly affect the transformation of soil nitrogen and the change in soil bacterial community in tea garden, which provided a theoretical basis for tea garden to cope with adverse weather changes and maintain the stability of tea garden soil ecosystem.