| Abstrakt: |
Influencing mechanism of nitrogen (N) fertilization on soil diazotrophs of legumes remains unclear. Further study on the effect of different nitrogen application rates on soil nitrogen-fixing is of critical importance for high-efficiency nitrogen application of peanut field and agricultural sustainability development. We used the non-nodulating (BL) and nodulating (Huayu 22, HY22) peanuts as experimental materials, with four N application rates arranged, including N0 (without N application, 0 kg hm-2), N60 (N reduced-application, 60 kg hm-2), N120 (N common-fertilization, 120 kg hm-2), and N180 (N over-application, 180 kg Hm-2). The qRT-PCR and Illumina high-throughput sequencing of nifH gene were used to analyze soil diazotrophic abundance, diversity, and community composition. Results showed that: (1) N fertilization significantly increased the contents of soil N fraction. Especially at N120, the soil microbial biomass carbon and dissolved organic carbon of nodulating peanut were significantly higher than that of non-nodulating peanut. The podding yields of non-nodulating peanut increased positively and linearly with the increasing N rates, while those of nodulating peanut was unaffected by N fertilization. (2) Under N fertilization, soil nifH copies of non-nodulating peanut were inhibited, while that of nodulating peanut decreased firstly and then increased with N rates increased. (3) N fertilization reduced firstly and then enhanced the soil diazotrophic diversity from non-nodulating peanut with N rates, while N fertilization increased firstly and then decreased that from nodulating peanut, with peak value at N120. (4) Nonrank_ Bacteria and Proteobacteria were the predominated phyla. N fertilization altered the soil diazotrophic community composition of non-nodulating peanut, with dominant genera being nonrank_Bacteria (N0), unclassified_Cyanoabcteria (N60), nonrank_ Bacteria (N120), and Skermanella (N180), respectively, and NO3-N being the overriding determinative factor, while exerted no effect on that of nodulating peanut (being dominated by unclassified_Proteobacteria and Skermanella except N120). The different responses of soil nitrogen-fixing bacteria to nitrogen application level between non-nodulating peanut and nodulating peanut may be due to the influence of different nitrogen sources (nitrogen fixed by nodules vs. N fertilizer). In conclusion, 120 kg hm-2 was the best for nitrogen-fixation of peanut field and thus agricultural production among the studied N rates. [ABSTRACT FROM AUTHOR] |
