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Maize straw is more effective than maize straw biochar at improving soil N availability and gross N transformation rate |
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| Authors: | Zunqi Liu Na Xu Ting Cao Zhengfeng An Xu Yang Tianyi He Tingting Yang Jun Meng |
| Institution: | 1. Key Laboratory of Biochar and Soil Improvement, Ministry of Agriculture and Rural Affairs, National Biochar Institute, Shenyang Agricultural University, Shenyang, China;2. Key Laboratory of Biochar and Soil Improvement, Ministry of Agriculture and Rural Affairs, National Biochar Institute, Shenyang Agricultural University, Shenyang, China
Contribution: Data curation, ?Investigation;3. Key Laboratory of Biochar and Soil Improvement, Ministry of Agriculture and Rural Affairs, National Biochar Institute, Shenyang Agricultural University, Shenyang, China Contribution: Writing - review & editing;4. Department of Renewable Resources, University of Alberta, Edmonton, Alberta, Canada Contribution: Writing - review & editing;5. Key Laboratory of Biochar and Soil Improvement, Ministry of Agriculture and Rural Affairs, National Biochar Institute, Shenyang Agricultural University, Shenyang, China Contribution: ?Investigation, Writing - review & editing;6. Key Laboratory of Biochar and Soil Improvement, Ministry of Agriculture and Rural Affairs, National Biochar Institute, Shenyang Agricultural University, Shenyang, China Contribution: ?Investigation, Funding acquisition;7. Key Laboratory of Biochar and Soil Improvement, Ministry of Agriculture and Rural Affairs, National Biochar Institute, Shenyang Agricultural University, Shenyang, China Contribution: ?Investigation |
| Abstract: | Soil nitrogen (N) transformation is vital in determining farmland N availability. Although many studies have investigated the effect of biochar on N retention and loss via leaching and gaseous emissions, few have determined the dynamics of gross N transformation during crop growth in long-term biochar-amended soils and compared the effect of the biochar with that of its feedstock. In this study, we conducted a five-time field measurement of soil gross N turnover rates via 15N isotope pool dilution during maize growth in 2021. Three treatments were employed, including no amendment, biochar and straw applied annually at rates of 2.63 and 7.50 t ha?1, respectively, since 2013. The results showed that biochar did not change the rate of gross N mineralisation when compared with no amendment, but straw increased it by 139% in August, resulting in significantly higher cumulative gross N mineralisation than biochar and no amendment (701 vs 489 and 499 mg kg?1 in 200 d). The inconsistent influence was attributed to the fact that inherent biochar-N was recalcitrant and could not be mineralized like the straw. The gross nitrification rate was decreased by 72.9% and 77.4% by biochar and straw application, respectively, in June relative to no amendment, but then it increased from July to August in the straw treatment as a result of the elevated gross N mineralisation rate. The decreased nitrification in the biochar treatment was an outcome of the synergetic effect of a low ammonium pool (?59.4%) and a high gross ammonium immobilisation rate (+263%), which was likely due to excessive fertilizer N loss and abiotic adsorption to biochar. Meanwhile, biochar amendment inhibited bacterial 16S and fungal ITS genes, as well as ureC and bacterial and archaea-amoA gene copies. In conclusion, straw is more effective than biochar at improving soil N transformation and availability in the long term. |
| Keywords: | 15N isotope pool dilution farmland soil gross N transformation long-term biochar effect N availability |