小麦秸秆焚烧对土壤有机质积累和微生物活性的影响

Effect of wheat straw burning on soil organic matter accumulation and microbial activity

【目的】焚烧作物秸秆是常见的处理农业废弃物减少病虫害和增加土壤养分的方法。但秸秆焚烧污染大气,妨碍农业健康发展。前人对秸秆焚烧造成大气污染已研究颇多,而对土壤环境所受影响的探究较少。本文选取焚烧不同小麦秸秆量的耕层土壤为研究对象,分析秸秆焚烧在短期内对土壤有机质积累和土壤微生物活性的影响。【方法】利用田间试验,设置对照（CK）、秸秆减量焚烧（0.24 kg/m^2,A1）、全量焚烧（0.48 kg/m^2,A2）和增量焚烧（0.72 kg/m^2,A3）4种处理。将秸秆均匀覆盖在地表进行焚烧,并对残留较多的部分进行补充焚烧,以确保秸秆焚烧完全。焚烧完成5 h后,待土壤温度恢复正常,采集0—5 cm、5—10 cm、10—20 cm土壤样品,分析各层次土壤有机质含量、含水量、微生物数量和土壤酶活性。【结果】秸秆焚烧对0—5 cm土层的有机质含量、含水量、微生物数量及土壤酶活性影响显著,各处理均表现出减少的趋势。有机质含量下降了6.37%-19.47%,含水量减少22.15%-39.19%;细菌数量减少52.26%-75.25%,真菌减少45.21%-63.29%,放线菌减少46.87%-68.26%。蔗糖酶活性降低14.19%-30.75%,脲酶活性降低7.81%-25.48%,过氧化氢酶活性降低9.63%-39.53%,磷酸酶活性降低11.36%-40.44%;各处理与CK间大多呈显著差异。5—20 cm土层中各指标无显著变化。焚烧处理各指标的减少量均表现出A3〉A2〉A1的趋势,不同秸秆焚烧量之间大多差异显著。相关性分析表明,秸秆焚烧量与有机质含量、含水量、土壤微生物数量和酶活性之间呈显著负相关关系。【结论】小麦秸秆焚烧在短期内显著降低了0—5 cm土层中的有机质含量和微生物活性,而对5—20 cm土层的土壤影响不显著。小麦秸秆焚烧对土壤环境的影响强度随秸秆量的增多而加大。焚烧量与有机质含量、含水量、土壤微生物数量和酶活性之间呈显著负相关关系。鉴于秸秆焚烧对土壤肥力的长期效应以及对土壤理化性质影响的复杂性,焚烧对土壤有机质积累和微生物群落的影响还需要长期定位试验来探讨。

【Objectives】Open burning of agricultural waste is practiced to clear the surface biomass from land,to control pests and diseases,and to return some nutrients. Emissions from field burning activities deteriorate local air quality and seriously impede agricultural development. Recently many studies had been conducted to assess air pollution caused by straw burning. However,data are relatively limited in change of soil physical and organic subsequent to straw burning. Topsoil of different straw burning quantity was collected to study the immediate effect of straw burning on content of soil organic matter and soil microbial activity. 【Methods】A field experiment wasestablished in June 2012. The experimental treatments included 4 levels of amount of burned wheat straw： no burning（ CK）,decrement group（ 0. 24 kg / m^2,A1）,normal group（ 0. 48 kg /m^2,A2） and increment group（ 0.72 kg / m^2,A3）. The wheat straw was put evenly over soil surface and then was burned,and the remained wheat straws were additionally burned in order to make straw burnt completely. After five hours,when soil temperature had returned to normal,soil samples were collected from 0-5,5-10 and 10-20 cm depth of soil in each treatment and analyzed through laboratory experiment. To elucidate the specific effect of burning wheat straw on soil environment,change of indicators,soil organic matter content,moisture content,microorganism quantity and enzyme activities in each layer of soil,were analyzed. 【Results】Burning wheat straw had significant influence on topsoil. The indicators of soil constituents were reduced with different degrees in different treatments. In the layer of0- 5 cm,the content of soil organic matter and moisture was reduced by 6. 37%- 19. 47% and 22. 15%- 39.19% respectively. The quantities of bacteria,fungi and actinomyces were respectively decreased by 52. 26%- 75.25%,45. 21%- 63. 29%,46. 87%- 68. 26%. Activities of sucrase,urease,catalase and phosphatase were decreased by 14. 19%- 30. 75%,7. 81%- 25. 48%,9. 63%- 39. 53% and 11. 36%- 40. 44% respectively.There were significant differences between most combustion treatments and the control, while there was no significant difference in the 5-20 cm soil layer. The content of each indicator was decreased in the order of A3〉 A2〉 A1. The combustion treatments with different amount of straw mostly had significant difference between each other. The correlation analysis indicated that amount of straw burning had significantly negative correlations with soil organic matter content,moisture,soil microbial quantity and soil enzyme activity. 【Conclusions】The results indicated that wheat straw burning significantly reduced soil organic matter content and soil microbial activity in topsoil（ 0-5 cm） in a short time,and the impact strength was proportional to the amount of burned straw. In the layer of 5-20 cm,the effect of the straw burning was small. The correlation analysis indicated that straw burning amount had significantly negative correlations with soil organic matter content,moisture,soil microbial quantity and soil enzyme activity. Due to long- term effect of straw burning on soil fertility and the complexity of the effect on the physical and chemical properties in soil environment of straw burning,long- term in- situ study should be carried out to better assess effect of wheat straw burning in field.