ABSTRACT
Long-term fertilization can change the supply of soil carbon and nitrogen (N), with consequences on the abundance and community structure of soil microorganisms. Based on the long-term fertilization positioning experiment station of brown earth, we analyzed the dynamics of soil ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) under different fertilization treatments, including no fertilization (CK), low level of inorganic N fertilizer (N2), high level of inorganic N fertilizer (N4), and organic manure combined with inorganic N fertilizer (M2N2), aiming to provide a basis for microbiological mechanism of soil N transformation and improvement of soil fertility. The results showed that the ratio of AOA to AOB abundance was 2.28-61.95 under different fertilization treatments. Compared with that in CK, the AOA abundance was reduced by 1.6%-13.6% after long-term fertilization. The abundance of AOB in N4 treatment decreased first and then increased with soil depths, but with contrary results in other treatments. The Shannon diversity index (H), evenness index (J), and Simpson index (S) of AOB were higher than those of AOA. The AOB diversity was increased at 0-20 cm soil layer in M2N2 treatment, while that of AOA was decreased. Soil AOB clustered with soil depths, and neither AOA nor AOB community clustered with fertilization treatments. In summary, long-term fertilization altered the composition of AOA and AOB. AOA was sensitive to environment, whereas AOB was more abundant and stable.
Subject(s)
Ammonia , Soil , Archaea , Bacteria , Nitrification , Oxidation-Reduction , Phylogeny , Soil MicrobiologyABSTRACT
BACKGROUND: Anthranilic diamide derivatives are among the most important classes of synthetic insecticides. Moreover, the 1,2,4-oxadiazole heterocycle, a bioisostere of amide, has been extensively used in pesticides. In order to discover novel molecules with high insecticidal activities, a series of anthranilic diamide analogues containing 1,2,4-oxadiazole rings were designed and synthesised. RESULTS: A series of novel anthranilic diamide derivatives containing 1,2,4-oxadiazole were obtained, and confirmed by 1 H and 13 C nuclear magnetic resonance and high-resolution mass spectrometry. The structure of 3-bromo-N-(4-chloro-2-methyl-6-{3-[(methylsulphonyl)methyl]-1,2,4-oxadiazol-5-yl}phenyl)-1-(3-chloropyridin-2-yl)-1H-pyrazole-5-carboxamide was further characterised by X-ray diffraction analysis. In addition, bioassays showed that most of the newly synthesised compounds displayed 100% mortality against Plutella xylostella at 100 mg L-1 , and compound 3IIl showed 90% larvicidal activities at a concentration of 0.5 mg L-1 . The LC50 value of 3IIl was 0.20 mg L-1 , which indicated that it may be used as a potential leading compound for further structural optimisation. Furthermore, brief comparative molecular field analysis (CoMFA) models were established to study the structure-activity relationships (SARs) of the title compounds. CONCLUSION: Compound 3IIl may be used as a potential leading compound for further structural optimisation, and SARs and CoMFA models could provide reliable clues for further structural optimisation. © 2016 Society of Chemical Industry.
