水稻土中矿物对绿肥残体转化的作用特征及潜在机制

The transformation of cover crop residue in soil relate closely to the improvement of soil productivity and the sequestration of soil organic carbon. The CO2、CH4 and humic acid, fulvic acid, humin which formed from the decomposition of 13C labeled milk vetch residue in paddy soil without and with the addition of a little amount of kaolinite or hydromica, goethite, ferrihydrite, gibbsite, non-crystalline Al oxide, birnessite within 360 days are chosen as the research objects in the current project. The influences of minerals on the release of CO2、CH4, the constitute, structure and property of humic acid, fulvic acid, humin, and the relationship between mineralization and humification of organic matter from milk vetch residue will be studied. The effects of minerals on the diversity and composition of soil functional microorganisms and the constitute, structure and property of dissolved, free, aggregated and mineral associated organic matter from milk vetch residue then will be elucidated. By analyzing the relationship of the influences of mineral on the mineralization and humification of organic matter from milk vetch residue with the effects of mineral on the characteristics of soil microorganisms and typical fraction of soil organic matter, the mechanisms of the influence of minerals on the transformation of cover crop residue in paddy soil will be clarified. The understanding of the transformation and sequestration of organic matter in soil will be promoted, the effective application of cover crop in paddy soil will also be improved.

绿肥残体在土壤中的转化与土壤地力提升和固碳减排紧密相关。本项目选取13C标记的紫云英残体在不添加和少量添加高岭石或水云母、针铁矿、水铁矿、三水铝石、非晶形铝氧化物、水钠锰矿的红壤性和潮土性水稻土中腐解360天产生的CO2、CH4和胡敏酸、富里酸、胡敏素为研究对象，分析矿物对水稻土中源自绿肥残体的CO2和CH4释放、腐殖质的组成结构和性质、以及矿化和腐殖化相互关系的影响，探讨矿物引起的土壤功能微生物多样性、群落组成等性状以及源自绿肥残体的水溶态、游离态、团聚体态、矿物结合态有机质的含量结构性质等性状的变化。通过分析矿物对水稻土中绿肥残体矿化、腐殖化及二者相互关系的影响与矿物引起的土壤功能微生物性状和土壤各形态有机质性状变化的关系，阐释水稻土中矿物对绿肥残体转化的作用特征及潜在机制，为深入理解有机质在耕地土壤中的转化和固定，有效应用绿肥培肥稻田土壤提供科学依据。

绿肥残体在土壤中的转化与土壤地力提升和固碳减排紧密相关。本项目研究了矿物对绿肥残体在红壤性和潮土性水稻土中转化的影响及其与矿物引起的土壤微生物、相关酶活性、各形态有机质和基本理化性质变化的关系，探究水稻土中矿物对绿肥残体转化的潜在作用机制。取得的主要结果如下：1. 在淹水条件下，伊利石、针铁矿、水铁矿均减少了两种水稻土中源自土壤的CO2和CH4累积释放量，水铁矿增加了源自绿肥的CO2累积释放量，针铁矿和水铁矿在红壤性水稻土中显著增加了源自绿肥的CH4累积释放量而在潮土性水稻土中减少了源自绿肥的CH4累积释放量；在不淹水条件下，供试矿物均减少了两种水稻土中源自绿肥的CO2累积释放量。2. 供试矿物在淹水条件下增多了红壤性水稻土中源自绿肥的DOM而减少了潮土性水稻土中源自绿肥的DOM，针铁矿、水铁矿在不淹水条件下减少了两种水稻土中源自绿肥的DOM。3. 供试矿物尤其是水铁矿在淹水条件下减少了潮土性水稻土中源自绿肥的MBC，在不淹水条件下减少了红壤性水稻土中源自绿肥的MBC。4. 供试矿物在淹水条件下显著减少了两种水稻土中真菌残体碳含量，针铁矿在不淹水条件下显著增加了潮土性水稻土中微生物残体碳含量。5. 供试矿物在淹水条件下减少了水稻土中真菌丰富度和细菌群落多样性，水铁矿在不淹水条件下显著减少了真菌丰富度。6. 矿物使土壤的C/N增大，pH降低，在淹水条件下还使Eh增大；水铁矿在淹水条件下增大了β-葡萄糖苷酶的活性，在不淹水条件下减小了β-葡萄糖苷酶活性。7. 在淹水条件下，矿物通过调节绿肥碳的微生物利用率、土壤β-葡萄糖苷酶活性等因子调节源自绿肥的CO2释放，矿物在红壤性水稻土中通过调节源自绿肥的DOM和MBC、绿肥碳的微生物利用率、土壤真菌多样性、真菌残体碳含量等因子调节源自绿肥的CH4释放，而在潮土性水稻土中通过调节土壤总氮含量、C/N、真菌丰富度等因子调节源自绿肥的CH4释放；不淹水条件下，矿物通过调节土壤pH、C/N、微生物残体碳含量等因子调节源自绿肥的CO2释放。这些结果为深入理解水稻土中有机质的转化和固定，有效应用绿肥培肥土壤提供了科学依据。