水稻秸秆添加对不同种稻年限黑土CH4排放特征的影响

  目的  评估水稻秸秆添加对东北地区不同种稻年限黑土CH₄的排放的影响，以期为黑土水稻田秸秆还田提供理论依据。  方法  不同种稻年限（0、12、35、62和85 a）黑土，分别设不添加（CK）和添加1%水稻秸秆（S）处理，进行淹水培养试验（培养温度为20 ℃，淹水层为1 cm），测定土壤CH₄排放通量及累积排放量，比较不同种稻年限土壤对水稻秸秆添加响应的差异。  结果  在淹水培养期间（150 d），添加水稻秸秆处理各种稻年限土壤CH₄排放通量（0.00 ~ 3.33 mg kg?1 d?1）显著（P > 0.05）高于未添加秸秆处理（0.00 ~ 0.13 mg kg?1 d?1），未添加和添加水稻秸秆处理土壤CH₄排放主要集中于淹水培养的前80 d和60 d。未添加水稻秸秆处理土壤CH₄累积排放量为0.04 ~ 4.45 mg kg?1，不同年限稻田土壤CH₄累积排放量差异不显著（P > 0.05）。添加水稻秸秆处理土壤CH₄累积排放量为29.64 ~ 91.08 mg kg?1，显著高于未添加水稻秸秆处理（P < 0.05），且12 a和35 a土壤CH₄累积排放量显著高于0 a、62 a和85 a（P < 0.05）。未添加和添加水稻秸秆处理土壤CH₄累积排放量与土壤有机碳、可溶性有机碳氮和铵态氮含量呈显著正相关（P < 0.01）。添加水稻秸秆处理土壤CH₄累积排放量还与土壤β-葡萄糖苷酶活性呈显著负相关（P < 0.05），土壤CH₄累积排放量增量也与土壤有机碳含量也呈显著线性正相关（P < 0.01）。水稻秸秆添加后土壤可溶性有机氮含量是影响土壤CH₄排放的直接因素，土壤可溶性有机碳和铵态氮含量及β-葡萄糖苷酶活性是影响土壤CH₄排放的间接因素。  结论  水稻秸秆添加显著促进了黑土不同种稻年限土壤CH₄排放，种稻年限越长，水稻秸秆添加后土壤CH₄排放量越少。本试验条件下，黑土种稻年限大于35年时，水稻秸秆还田带来的土壤CH₄排放量相对较小。

Effect of Rice Straw Addition on CH4 Emission in Black Soil with Different Rice Planting Years

  Objective  The effect of rice straw addition on soil CH₄ emission in Black soil with different rice planting years in Northeast China needed to be evaluated, which will provide to provide a theoretical basis for the return of rice straw in paddy field of Black soil.  Method  Flooding incubation experiment in a laboratory for 150 days (at 20 ℃, with 1 cm water-flooded layer) was carried out, and 1% rice straw was added to black soils with different rice planting years (0, 12, 35, 62 and 85 years), and the soil without rice straw addition was used as the control. The CH₄ emission flux and cumulative emissions from soil were determined.  Result  During flooding incubation period (150 days), the soil CH₄ emission flux (0.00 - 3.33 mg kg?1 d?1) from the treatments with rice straw was significantly higher than that from the treatments without rice straw (0.00 - 0.13 mg kg?1 d?1). The CH₄ emission from the treatments without and with rice straw mainly occurred in the first 80 days and the first 60 days, respectively. The cumulative emissions of soil CH₄ from the treatments without rice straw were 0.04 - 4.45 mg kg?1, there was no significant difference in soil CH₄ cumulative emissions in different rice planting years (P > 0.05). The cumulative emissions of soil CH₄ from the treatments with rice straw were 29.64 - 91.08 mg kg?1, which was significantly higher than that of without rice straw treatments (P < 0.05), and the cumulative emissions of soil CH₄ from 12 years and 35 years were significantly higher than that of 0 year, 62 years and 85 years (P < 0.05). The cumulative emissions of CH₄ from the treatments without and with rice straw positive correlated significant (P < 0.01) with soil organic carbon (SOC), dissolve organic carbon (DOC), dissolve organic nitrogen（DON）and NH₄ + ?N. The cumulative emissions of CH₄ from the treatments with rice straw negatively correlated significantly (P < 0.05) with β- Glucosidase activity, the cumulative emission increment of CH₄ positive correlated significant (P < 0.01) with SOC and DON in the treatments with rice straw addition, which means that the SOC and DON are the main affecting factors for CH₄ emission. While the DOC, NH₄ + ?N and β -glucosidase activities were the indirect factors affecting soil CH₄ emission.  Conclusion  These results suggest that the addition of rice straw significantly promots the CH₄ emission in Black Soil with different rice planting years, the longer the years of rice planting, the soil CH₄ emission is relatively lower. Therefore, the soil CH₄ emission increases from the treatments with rice straw addition is relatively small in more than 35-year rice planting Black soils