Effect of chemical fertilization and green manure on the abundance and community structure of ammonia oxidizers in a paddy soil

Abstract

Ammonia oxidization is a critical step in the soil N cycle and can be affected by the fertilization regimes. Chinese milkvetch (Astragalus sinicus L., MV) is a major green manure of rice (Oryza sativa L.) fields in southern China, which is recommended as an important agronomic practice to improve soil fertility. Soil chemical properties, abundance and community structures of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) in a MV-rice rotation field under different fertilization regimes were investigated. The field experiment included six treatments: control, without MV and chemical fertilizer (CK); 100% chemical fertilizer (NPK); 18 000 kg MV ha -1 plus 100% chemical fertilizer (NPKM1); 18 000 kg MV ha -1 plus 40% chemical fertilizer (NPKM2); 18 000 kg MV ha -1 alone (MV); and 18 000 kg MV ha -1 plus 40% chemical fertilizer plus straw (NPKMS). Results showed that NPKMS treatment could improve the soil fertility greatly although the application of 60% chemical fertilizer. The abundance of AOB only in the MV treatment had significant difference with the control; AOA were more abundant than AOB in all corresponding treatments. The NPKMS treatment had the highest AOA abundance (1.19 × 10 8 amoA gene copies g -1 ) and the lowest abundance was recorded in the CK treatment (3.21 × 10 7 amoA gene copies g -1 ). The abundance of AOA was significantly positively related to total N, available N, NH4 + -N, and NO3 --N. The community structure of AOA exhibited little variation among different fertilization regimes, whereas the community structure of AOB was highly responsive. Phylogenetic analysis showed that all AOB sequences were affiliated with Nitrosospira or Nitrosomonas and all AOA denaturing gradient gel electrophoresis (DGGE) bands belonged to the soil and sediment lineage. These findings could be fundamental to improve our understanding of AOB and AOA in the N cycle in the paddy soil.Key words: Abundance, ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB), Astragalus sinicus, community structure, Chinese milk vetch, soil chemical properties. INTRODUCTIONAppropriate fertilizer application is an important management practice to improve soil fertility. In recent years, due to the rapid population growth and continuous decline in the amount of cultivated land area, the application rate of fertilizer keeps on rising in tropical and subtropical regions of China in order to obtain high crop production. However, the long-term inappropriate fertilization has caused many environmental problems, such as high acidity, low nutrients in cultivated land and unbalanced ecosystem (Chen et al., 2010). Recently, soil quality has gained much attention as a result of environmental issues related to soil degradation and production sustainability under different farming systems (Galantini and Rosell, 2006). Chinese milk vetch (Astragalus sinicus L., MV) is considered as the most popular green manure in paddy field of South China, due to its high N-fixing potential and better growth under wet paddy soi...

Response of rhizosphere soil microbial to Deyeuxia angustifolia encroaching in two different vegetation communities in alpine tundra

“…In herbaceous soil samples, AOA was positively correlated with TOC, TP, and C/N and negative correlated with TK, while shrub soil samples had strong negative correlations with available nutrients (AN, AK). Significant correlations between AOA abundance and organic C, total N, and available N observed in the present study support the idea that C and N conditions may be a key factor affecting the population size of AOA in acidic soil 28 63 64 65 . Ammonia-oxidizing bacteria (AOB) may respond more strongly than ammonia-oxidizing archaea to increased N availability 66 67 .…”

“…An invasive species may influence soil nitrogen cycling through direct interactions with the soil microbial community or through its effects on soil nitrogen itself 26 . For example, the abundance of ammonia-oxidizing bacteria (AOB) and ammonia oxidizing archaea (AOA) may be directly influenced by organic carbon, total nitrogen, and availability of ammonium 27 28 , N enrichment is shown to change the abundance of functional N-fixation genes ( nifH ) 29 30 . In turn, nitrogen fixing bacteria population sizes could increase N input in rhizosphere was conducive to plant invasion 31 .…”

Soil ammonia-oxidizing archaea in a paddy field with different irrigation and fertilization managements

“…The abundance of AOA had richer than that of AOB in acidic paddy soils under different irrigation and fertilization regimes (Supplementary Figure S1 ). A lower abundance of AOB in the same type of rice paddy soil has also been reported in other studies 3 , 18 , because AOA could have a potentially competitive advantage over AOB in acidic and oligotrophic soil environments. Furthermore, AOA were more stable and resilient than AOB under different environmental conditions 19 .…”