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| Effects of earthworms on nitrogen uptake by lettuce and microbial nitrogen fixation after nitrogen application |
| Received:August 20, 2019 |
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| KeyWord:earthworm;urea nitrogen;soil nitrogen;microbial biomass nitrogen;nitrogen uptake by plants |
| Author Name | Affiliation | E-mail | | NA Li-ping | College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China | | | LI Yu-ting | College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China | | | HE Ji-qiang | College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China | | | LI Jian-feng | Shandong Binzhou Agricultural Bureau, Binzhou 256600, China | | | WU Yu-peng | College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, China | wyp19851205@126.com |
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| Abstract: |
| In exploring the impact of the earthworm on nitrogen uptake by plants and microbial nitrogen fixation after urea application, a pot experiment was conducted to compare the difference in plant nitrogen content and explore the dynamic of soil microbial biomass between earthworm(Metaphire guillelmi)and non-earthworm treatments after 15N-labeled urea application. Results showed that there was no significant difference in plant nitrogen content among treatments, while earthworm presence increased the whole plant biomass, leading to an increase in total nitrogen uptake of about 30.8%. In terms of distribution ratio, earthworm presence significantly increased the proportion of soil nitrogen absorbed by the plant and reduced the proportion of applied urea nitrogen absorbed by the plant. There was no significant change in total nitrogen between earthworm presence and earthworm absence throughout the experiment, as nitrogen from fertilizer in the soil decreased gradually; however, the decrease in nitrogen was faster in the earthworm-treated soil. The microbial biomass nitrogen(MBN) content initially decreased and then increased, and high levels of MBN content were observed in earthworm treatments, especially at days 5 and 30. However, the content of fertilizer nitrogen in MBN was always lower than that in the control. Throughout the experiment, the content of soil dissolved organic nitrogen initially decreased and then increased, which was consistent with the trend for MBN. The content of ammonium nitrogen(NH4+-N)in the earthworm treatment was lower than that in control treatment, while the content of nitrate nitrogen(NO3--N) was not significantly different. In conclusion, earthworms can promote growth and nitrogen uptake by plants by regulating microbial biomass to form a buffer pool, but this regulation mainly acts on native soil nitrogen rather than the newly applied urea nitrogen. |
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