| 土壤水分和碳氮有效性对水稻土CH4与CO2排放的影响 |
| 摘要点击 1636 全文点击 106 投稿时间：2024-06-18 修订日期：2024-08-07 |
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| 中文关键词 水稻土 土壤水分 碳氮有效性 甲烷（CH4） 二氧化碳（CO2） |
| 英文关键词 paddy soil soil water carbon and nitrogen availability CH4 CO2 |
| DOI 10.13227/j.hjkx.20250660 |
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| 中文摘要 |
| 近年来，社会经济快速发展和人们膳食结构改善驱动了稻田转为旱地作物种植，改变了土壤水分含量和碳氮有效性及其引起的温室气体排放强度. 因此，有必要研究稻田转为旱地，特别是该土地利用方式转变初始阶段，土壤水分变化和碳氮有效性对温室气体甲烷（CH4）和二氧化碳（CO2）排放的影响及其关键控制因素. 研究采集了长期种植水稻的土壤和由稻田转为旱地作物种植的土壤样品，通过室内模拟试验将水稻土设置淹水（水土比为2∶1）和由淹水到缓慢落干处理（土壤水分由水土比2∶1缓慢降低到70%田间持水量，随后保持稳定不变），与旱地土壤（土壤水分维持70%田间持水量）对比分析. 每一种水分梯度下分别设置不添加葡萄糖（C）和NH4Cl（N）、添加C、添加N和添加CN这4个处理，培养过程中定期测定CH4和CO2排放通量、土壤生物化学性质，并计算培养期间（培养结束时的值减去初始值）土壤微生物生物量碳（ΔMBC）、溶解性有机碳（ΔDOC）和矿质氮（ΔMineral-N， 含ΔNH4+-N和ΔNO3--N）的含量变化，以期探明土壤水分变化和碳氮有效性及其交互作用对水稻土CH4和CO2排放的影响. 研究结果表明，与淹水处理相比，水稻土落干处理CH4排放显著降低了95%，CO2排放增加了46%. 落干水稻土CH4和CO2排放[累计排放量（以C计，下同）分别为1.36 mg·kg-1和584.13 mg·kg-1]明显高于旱地土壤（0.01 mg·kg-1和407.70 mg·kg-1）. 在淹水水稻土中，与碳氮不添加处理相比，碳添加处理CH4排放显著增加了40%，氮添加处理CH4排放显著降低了63%，碳氮同时添加对CH4排放无显著影响. 在落干水稻土中，只添加碳处理CH4排放显著增加了48%，其他处理无显著差异. 在旱地土壤中，碳氮有效性对CH4排放无显著影响，但均显著增加CO2排放（45%~109%）. 碳氮有效性对淹水水稻土CO2排放无显著影响，但落干水稻土同时添加碳氮处理CO2排放显著增加了36%. 土壤水分变化和氮添加对CH4排放无显著交互作用，而土壤水分变化和碳及碳氮同时添加交互影响CH4排放，土壤水分变化和碳氮有效性对CO2排放的影响无明显的交互作用. 淹水稻田落干转为旱地降低了土壤pH、DOC、MBC和NH4+-N含量，增加了NO3--N含量，碳氮添加显著影响土壤生物化学学性质. 相关性分析结果表明，CH4排放与土壤pH、ΔMBC和ΔNH4+-N显著正相关，与ΔNO3--N显著负相关，而CO2排放与ΔNO3--N显著正相关，与pH、ΔDOC、ΔMBC和ΔNH4+-N显著负相关，土壤水分变化和碳氮有效性引起的土壤生物化学性质的变化是水稻土CH4和CO2排放的主要影响因素. 综上所述，土壤水分和碳氮有效性变化通过影响土壤生物化学性质调控CH4和CO2排放，水稻土排水落干是减少CH4排放的有效措施，但需考虑短期内CO2排放增加的风险. 建议在制定稻田利用方式转变过程中温室气体减排策略时，需综合考虑水分和碳氮管理的影响，减少淹水时间并合理施肥，以实现温室气体有效减排和农业绿色可持续生产. |
| 英文摘要 |
| In recent years， the rapid socio-economic development and the improvement of people's diets have driven the conversion of paddy soil to upland crop cultivation， leading to changes in soil water content， carbon and nitrogen availability， and the intensity of greenhouse gas emission. Therefore， it is crucial to study the effects of changes in soil water content and carbon and nitrogen availability on greenhouse gas CH4 and CO2 emissions and identify the key controlling factors upon rice paddy conversion into upland field， especially during the initial stage of conversion. Soil samples used in the present study were collected from a long-term rice paddy field and an adjacent upland field previously converted from rice paddy. The paddy soil was set into submerged （water to soil ratio of 2∶1） and from submerged to a slowly draining treatment （water to soil ratio of 2∶1 slowly decreased to 70% field water capacity and then remained stable） and compared with the upland soil （soil water content remained at 70% field water capacity）. Under each water gradient， the soil was supplied with labile C and N to change substrate availability： ① control （no substrate addition）， ② C addition （glucose）， ③ N addition （NH4Cl）， and ④ C and N additions （glucose+NH4Cl）. CH4 and CO2 emissions and soil biochemical properties were measured regularly during the incubation period so as to investigate the effects of soil water content， carbon and nitrogen availability， and their interaction on CH4 and CO2 emissions in paddy soil. The changes in contents of soil microbial biomass carbon （ΔMBC）， dissolved organic carbon （ΔDOC）， and soil mineral N （ΔMineral-N， containing ΔNH4+-N and ΔNO3--N） over the incubation period were calculated by subtracting the initial values from the final values at the end of the incubation period. The results showed that as compared to the submerged condition， the drainage of submerged paddy soil significantly reduced CH4 emission by 95% on average and increased CO2 emission by 46% on average. The cumulative emissions of CH4 and CO2 were significantly higher in drained paddy soil （1.36 mg·kg-1 and 584.13 mg·kg-1 for CH4 and CO2， respectively） relative to those in upland soil （0.01 mg·kg-1 and 407.70 mg·kg-1）. CH4 emissions from the submerged paddy soil significantly increased by 40% after carbon addition and decreased by 63% after nitrogen addition. The simultaneous additions of carbon and nitrogen had little effect on the CH4 emissions from submerged paddy soil. CH4 emissions from the drained paddy soil increased significantly by 48% after carbon addition， but there was no significant difference among other substrate addition treatments. In upland soil， the additions of carbon and nitrogen had no significant effect on CH4 emissions but significantly increased CO2 emissions by 45%-109%. The additions of carbon and nitrogen had little effect on CO2 emissions in submerged paddy soil. The concurrent addition of carbon and nitrogen significantly increased CO2 emissions by 36% in drained paddy soil. The interactions between soil water change and N addition had no significant effect on CH4 emissions， while the interactions between soil water change and C and CN additions significantly affected CH4 emissions. No significant interactions between soil water change and C and N availability were observed for CO2 emissions. The conversion of submerged paddy to upland soil decreased soil pH， DOC， MBC， and NH4+-N contents but increased NO3--N content. The additions of carbon and nitrogen significantly affected soil biochemical properties. The results of correlation analysis showed that CH4 emissions were significantly positively correlated with soil pH， ΔMBC， and ΔNH4+-N and negatively correlated with ΔNO3--N among treatments. Conversely， CO2 emissions were significantly positively correlated with ΔNO3--N but negatively correlated with pH， ΔDOC， ΔMBC， and ΔNH4+-N. The changes of soil chemical and biological properties induced by soil water change and carbon and nitrogen availability were the main factors influencing CH4 and CO2 emissions from paddy soil. In summary， changes in soil water content and carbon and nitrogen availability affect CH4 and CO2 emissions by altering soil biochemical properties. Drainage of paddy soil is an effective measure to reduce CH4 emissions， but the risk of increased CO2 emissions during the short-term period upon drainage should be considered. Therefore， when developing strategies for rice paddy management， it is crucial to consider the combined effects of water and C and N management so as to achieve effective greenhouse gas mitigation and green and sustainable agricultural production. |
