Short-term Effect of Waterlogging on Mineral Nitrogen and Ammonia-oxidizing Microorganisms in Soil

【Objective】 Waterlogging is a common abiotic stress affecting crop growth and soil functions. The purpose of this paper is to experimentally investigate short-term effect of waterlogging on mineral nitrogen and ammonia-oxidizing microorganisms in the rhizosphere and bulk soil of winter wheat. 【Method】 Waterlogging was imposed at the anthesis stage, and lasted 0 days, 3 days and 5 days, respectively. In each treatment, we measured the mineral nitrogen and the copy numbers of ammonia oxidizing microorganisms in the soil at the end of surface waterlogging, the end of subsurface waterlogging, as well as two days after the waterlogging completely eased. 【Result】 Compared with the control (without waterlogging), prolonged surface waterlogging promoted ammonium nitrogen and reduced nitrate nitrogen in both the rhizosphere and the bulk soil (P<0.05). Surface waterlogging lasting for 5 days significantly reduced the copy numbers of ammonia-oxidizing archaea (AOA-amoA) gene in the rhizosphere but reduced the ammonia-oxidizing bacteria biomass after the waterlogging eased. Redundancy analysis showed that the ammonium nitrogen and pH significantly affected the community of the ammonia oxidizing microorganisms in the bulk soil. Stepwise regression analysis showed that the contents of ammonium and nitrate nitrogen were both regulated by the ammonia-oxidizing archaea in the bulk soil during and after the waterlogging. In contrast, a decrease in water content in the rhizosphere did not show significant influence on ammonium nitrogen, but increased nitrate nitrogen. The increase in available phosphorus may accelerate the accumulation of ammonium nitrogen. 【Conclusion】 Mineral nitrogen content in soil recovered quickly after short-term waterlogging, and applying phosphate fertilizer can improve mineral nitrogen in the rhizosphere of winter wheat.