Effects of Water Supply Mode on Nitrogen Transformation and Ammonia Oxidation Microorganisms in a Tea Garden

Abstract

Drought limits tea yield and can also negatively impact its quality. In this study, constant humidity and dry–wet alternating modes were compared to determine their impacts on soil nitrogen transformation and ammonia-oxidizing microorganisms. Drought was found to reduce the soil NH4+-N concentration under the constant humidity mode, and the NO3−-N concentration was highest in 60% water-holding capacity (WHC) soil. Soil NO3−-N content increased rapidly after rewatering, and increasing the frequency of dry–wet watering resulted in a higher accumulation of NO3−-N. In the constant humidity mode, drought reduced the abundance of ammonia-oxidizing archaea (AOA), whereas that of ammonite-oxidizing bacteria (AOB) increased. Increases in drought duration and the frequency of dry–wet watering inhibited the activity of AOA under the dry–wet alternating mode, whereas the relative activity of AOB increased after rehydration. The water supply mode did not change the community structure of AOA or AOB at the genus level but affected their relative abundance. In the constant humidity mode, the contribution rate of AOA to nitrification potential (PNR) was 42.75–49.72%, whereas that of AOB was 50.28–57.25%. In the dry–wet alternating mode, the contribution rate of AOA to PNR increased, and the contribution rate of AOB decreased. Taken together, these findings indicate that ammonia oxidation might be primarily driven by AOA and AOB in weakly acidic and neutral soil. This study reveals the effects of different water supply modes on soil nitrogen transformation and ammonia-oxidizing micro-organisms and provides a scientific basis for improving nitrogen use efficiency.