Dataset for research entitled "Hydrochar as a potential soil conditioner for mitigating H⁺ production in the nitrogen cycle: A comparative study"

In this study, we investigated how rice-straw hydrochar would affect soil nitrification and nitrate leaching. We (1) determined how hydrochar addition interferes with nitrification mediated by soil microbes;(2) verified whether hydrochar input notably reduces nitrate leaching risks; and (3) elucidated the possible mechanisms by which hydrochar impacts soil nitrification and nitrate leaching relative to pyrochar.Our results showed that hydrochar addition mitigated the net nitrification rate by 3.75%~48.75% and 57.92%~78.19%, respectively, in contrast to the control and pyrochar treatments. This occurred mainly because a greater amount of dissolved organic carbon (DOC) was released from hydrochar (148.42 mg kg^-1~255.58 mg kg^-1) than the other treatments (117.13 mg kg^-1~122.22 mg kg^-1), which stimulated greater microbial nitrogen immobilization.The abundances of ammonia-oxidizing archaea (AOA) and bacteria (AOB) were dramatically elevated by 25.62%~153.19% and 12.38%-22.39%, respectively, in the hydrochar treatments because of DOC-driven stimulation. The cumulative leaching loss of NO₃^--N in soils amended with hydrochar was markedly reduced by 43.78%~59.91% and 61.70%~72.82% compared with that in the control and pyrochar treatments, respectively, becausehydrochar promoted the soil water holding capacity by 2.70%~9.04% and reduced the residual NO₃^--N content by 20.36%~36.21%.Collectively, we highlighted that (1) Hydrochar addition mitigated the increase in net H⁺production resulting from soil nitrification and the NO₃^--N leaching process; (2) Hydrochar can decrease the soil nitrification rate by providing abundant DOC and enhancing microbial nitrogen immobilization; (3) The promoting effect of soil nitrification caused by increased AOA and AOB abundance might be neutralized by intensive NH₄⁺-N assimilation in hydrochar-amended soils; (4) Hydrochar decreased the risk of NO₃^--N loss via leaching, as it promoted soil saturated water-holding capacity and reduced NO₃^--N content. A graphical abstract was also provided below to help understand the framework and results of this work.本研究探究了稻秆基水热炭（rice-straw hydrochar）对土壤硝化作用与硝酸盐淋溶的影响。具体研究内容包括：(1) 明确水热炭（hydrochar）添加如何干扰土壤微生物介导的硝化过程；(2) 验证水热炭输入是否可显著降低硝酸盐淋溶风险；(3) 阐明相较于热解炭（pyrochar），水热炭影响土壤硝化作用与硝酸盐淋溶的潜在作用机制。研究结果显示，相较于对照组与热解炭处理组，添加水热炭可使土壤净硝化速率分别降低3.75%~48.75%与57.92%~78.19%。该现象主要源于水热炭释放的溶解态有机碳（dissolved organic carbon, DOC）含量（148.42 mg·kg⁻¹~255.58 mg·kg⁻¹）显著高于其他处理组（117.13 mg·kg⁻¹~122.22 mg·kg⁻¹），进而促进了微生物的氮固持作用。受DOC驱动的刺激作用影响，水热炭处理组中氨氧化古菌（ammonia-oxidizing archaea, AOA）与氨氧化细菌（ammonia-oxidizing bacteria, AOB）的丰度分别显著提升25.62%~153.19%与12.38%~22.39%。相较于对照组与热解炭处理组，施加水热炭的土壤中硝态氮（NO₃⁻-N）的累积淋溶损失量分别显著降低43.78%~59.91%与61.70%~72.82%，这是由于水热炭可使土壤持水能力提升2.70%~9.04%，同时使残留硝态氮含量降低20.36%~36.21%。综上，本研究明确以下核心结论：(1) 施加水热炭可缓解土壤硝化作用与硝态氮淋溶过程所产生的净氢离子（H⁺）生成量增加；(2) 水热炭可通过提供丰富的溶解态有机碳并强化微生物氮固持作用，降低土壤硝化速率；(3) 氨氧化古菌与氨氧化细菌丰度提升所带来的土壤硝化促进效应，可被水热炭处理土壤中强烈的铵态氮（NH₄⁺-N）同化作用所抵消；(4) 水热炭可通过提升土壤饱和持水能力并降低硝态氮含量，降低硝态氮淋溶流失风险。本文下方还提供了图文摘要（graphical abstract），以帮助读者理解本研究的框架与核心结果。