Response of soil ammonia-oxidizing organisms on fertilization and mulch in Phyllostachys violascens stands

Abstract

For intensive management of Phyllostachys violascens stands, heavy winter mulching, to increase soil temperature, and winter fertilization are widely used techniques which affect the activity of soil ammonia oxidizing organisms. To understand the effects of mulch and fertilization on ammonia oxidizing bacteria (AOB)and ammonia oxidizing archaea(AOA)communities, two experiments were conducted:1)with a constant N fertilizer rate of 360 kg·hm-2 applied as m(N):m(P2O5):m(K2O)=16:16:16 and treatments(Tr) with mulch (Tr1)and no mulch(ck1);and 2) with mulch in each treatment and ck,three fertilizer combinations at a constant N rate of 360 kg·hm-2[Tr1(as above)——applied as a compound fertilizer,Treatment 2(Tr2)——applied N as urea,Treatment 3(Tr3)——applied fertilizer as urea and potassium chloride(KCl),and ck2——no fertilizer applied]. The community structure and functional gene abundance of soil AOB and AOA were measured using polymerase chain reaction——denaturing gradient gel electrophoresis(PCR-DGGE) and real-time——polymerase chain reaction (RT-PCR) with the Shannon diversity index being used for analysis. Results showed a majority of common AOB and AOA species represented by bands on DEEG profile were produced from the all treatments. The AOB community structure with no mulch(ck1) was different from the other treatments which received mulch in the winter season, and Tr3 was different from the other mulched treatments. The Shannon diversity index for AOB species with Tr1 was significantly higher(P＜0.05)than Tr3. The higher (P＜0.05)amoA abundance for both AOB and AOA was observed in Tr3. Results from the combination of PCR-DGGE and RT-PCR for both AOA and AOB, showed Tr3 best in species diversity and gene abundance of ammonia oxidizing organisms;whereas,Tr2 was worst. Thus,to sustain the activity of ammonia oxidizing organisms and to improve N recycling,urea in combination with KCl should be applied.