Response Of Soil Ammonia-oxidizing Microorganisms To Fertilizers And Nitrification Inhibitors And Its Relation To Nitrogen Transformation In Phyllostachys Edulis Plantations

The rapid development of bamboo industry has brought great economic and social benefits in recent years.The moso bamboo forest managers are making more yield and profit through increased use of fertilizers,which mainly include nitrogen fertilizer and compound fertilizer.But excessive fertilization could cause many environmental issues,including low efficiency of nitrogen fertilizers,Eutrophication and nitrous oxide?N₂O?emissions.Laboratory incubation experiment and field experiments were carried out to investigate effects of nitrification inhibitors incorporated with different fertilizers on microbial processes in nitrogen transformation.We determined soil N₂O flux,soil total nitrogen content,nitrification potential and soil microbial community characteristics.And soil microbial community characteristics were characterized by using PCR-DGGE and q PCR.Our aims are to 1)provide theoretical basis for soil management and the optimal fertilization scheme in moso bamboo forest;2)promote sustainable development of moso bamboo industry.We selected two major nitrification inhibitors commonly used in agriculture,dicyandiamide?DCD?and 3,4-dimethylpyrazole phosphate?DMPP?.The microcosm experiment had six treatments:?1?control?CK?;?2?only urea?Urea?;?3?applied with urea and 1%DMPP,the application rate of DMPP was 1% of applied fertilize N?1%DMPP?;?4?applied with urea and 1.5% DMPP?1.5%DMPP?;?5?applied with urea and 10% DCD?10%DCD?;and?6?applied with urea and 15% DCD?15%DCD?.The field experiment for analyzing the effects of nitrification inhibitors in moso bamboo forest had five treatments: 1)control?CK?;?2?only urea?Urea?;?3?applied with urea and1%DMPP?DMPP?;?4?applied with urea and15%DCD?DCD?;and?5?applied with stable compound fertilizer?SF?.Another field experiment in extensively managed moso bamboo forest had five different fertilizer treatments:?1?control?CK?;?2?only urea?Urea?;?3?applied with urea and KCl?NK?;?4?applied with urea andsaferock?NS?;and?5?applied with urea and Bamboo fertilizer?MBF?.We employed a randomized blocks design with three replications to carry out the two field experiments.Our results demonstrated that:?1?Results of the microcosm experiment indicated that applying urea had a positive effect on N₂O emission and ammonia oxidizers,especially Ammonia-oxidizing archaea?AOA?.Addition of nitrification inhibitors can effectively suppress N₂O emission and conversion of NH4+ to NO3-.Both of the nitrification inhibitors could significantly reduce the abundance of AOB and change the structure of AOB community,but they had weak inhibition effects on AOA community.AOB plays an important role in nitrogen transformation,particularly in the slight acid or neutral soil with high nitrogen.However,the relative importance of AOA increased with a decrease in p H and the ammonium nitrogen contents.DMPP and DCD worked by inhibiting the AOB community.But DMPP is more durable and efficient.To improve the use efficiency and durationof nitrification inhibitors,we suggest that 1)adjust the p H value to neutral;2)the optimal application rate of DMPP was 1% of applied fertilize N.?2?A follow-up field experiment during August 2010 and April 2015 shown that suppression effects of DMPP and DCD on N₂O emission,AOA and AOB communities and abundances of functional genes were similar to the microcosm experiment.DMPP and DCD pushed back the peak of N₂O production.And they had longer durations in April than in August.MBF had no effect on cumulative N₂O production compared with the Urea treatment.However,at the beginning of the MBF treatment?20 days?,DGGE fingerprints and microbial abundance shown weak suppression of AOB community by MBF.Using stabilized?DMPP?nitrogen fertilizers could not reduce the total N₂O losses.But it could effectively sustain the high ammonium nitrogen concentration and low nitrate and nitrite nitrogen concentrations in the soil,increase the nitrogen uptake by bamboo and improve the nitrogen use efficiency.The specific fertilizer strategies of DMPP for longer suppression effect deserve further investigation.?3?Several conclusions were drawn based on the different fertilizer treatments of the moso bamboo forest soil: 1)the long-term application of urea or urea combined with KClcaused soil acidification.And the application of urea combined with KCl suppressed some of ammonia oxidizers;2)although the long-term application of MBF caused soil acidification,it deceased the nitrification,and then improved the nitrogen use efficiency;3)in summary,applying urea with saferock?treatment NS?was the best fertilizer strategies,and should be promoted in moso bamboo forest management.