不同土壤水吸力与耕作方式对土壤压缩—回弹特性的影响

Effects of Soil Water Suction and Tillage Method on Soil Compressibility-Resilience Characteristics

    摘要
  • 摘要:
      目的  合理耕作方式是缓解土壤压实、提升土壤生产能力的有效措施，而土壤水分是影响土壤机械物理性能的重要因素，直接影响土壤耕作质量。通过研究不同土壤水吸力和耕作方式下土壤压缩曲线及模型拟合效果，分析土壤回弹—再压缩曲线变化及机械力学参数（预固结压力、压缩指数和回弹指数）差异，以期为农田土壤耕作和培肥提供科学依据。
      方法  通过不同土壤水吸力（S：50 kPa、100 kPa、630 kPa）和耕作方式（T：单一深翻（SF）、深翻 + 秸秆（SFJ）、地表旋耕 + 秸秆（XGJ））土壤的单轴压缩－回弹－再压缩固结试验，获得土壤压缩曲线和回弹再压缩曲线，进而计算出预固结压力、压缩指数和回弹指数。
      结果  Gompertz模型可以很好地拟合不同水吸力下不同耕作方式土壤的压缩曲线，其中低吸力段不同耕作土壤间孔隙比差异明显，表现为SFJ > XGJ > SF。耕作方式、水吸力及二者的交互作用对土壤压缩—回弹特性的影响表现为，同一耕作方式下土壤预固结压力随水吸力的增加而增加，同一水吸力条件下不同耕作方式土壤的预固结压力值表现为SF > SFJ > XGJ。土壤水吸力和耕作方式及二者的交互作用对压缩指数和回弹指数的影响均表现为土壤水吸力 > 交互 > 耕作方式。土壤压缩指数随水吸力的增加呈现先减小后增大的趋势变化，而回弹指数随水吸力的变化规律与之相反，即在水吸力100 kPa时压缩指数最小而回弹指数最大。
      结论  水吸力100 kPa（相当于55%田间持水量）下更适宜土壤耕作，深翻 + 秸秆还田（SFJ）可以有效的改善土壤压缩—回弹特性。

     

    Abstract:
      Objective  Reasonable tillage can mitigate soil compaction and improve soil productivity, and soil moisture affects directly tillage quality via influencing soil physical and mechanical properties. In order to provide a scientific basis for farmland soil cultivation and fertilization, the effects of soil water suction and tillage method on soil compression curve model and its fitting effects were studied, the characteristics of the resilience-recompression curve and the differences of mechanical parameters were analyzed.
      Method  A uniaxial compression-resilience-recompression consolidation experiment was conducted, which consisting of three levels of soil water suction (50 kPa, 100 kPa, 630 kPa) with three tillage methods (SF, single deep ploughing; SFJ, deep ploughing + straw; XGJ, surface rotary tillage + straw). The mechanical parameters were calculated including pre-compression stress, compression, and resilience index based on the obtained soil compression-resistance-recompression curve.
      Result  Gompertz model fitted well the compression curves of different tillage methods under different soil water suction levels. There was a significant difference of void ratio in the low suction section, and which was SFJ > XGJ > SF. The effects of tillage method, water suction and their interaction on soil compression-resilience characteristics showed that the pre-compression stress increased with the increase of soil water suction under the same tillage method, and soil pre-compression stress of different tillage method was expressed as SF > SFJ > XGJ under the same water suction level. The effects of soil water suction, tillage methods, and their interaction on the compression and resilience index were all expressed as soil water suction > interaction > tillage method. The compression index decreased firstly and then increased with the increase of soil water suction, while the resilience index changed with water suction in the opposite way. When the soil water suction was 100 kPa, the compression and resilience indices were minimum and maximum, respectively.
      Conclusion  Soil tillage was more suitable under soil water suction of 100 kPa（equivalent to 55% water-holding capacity）. SFJ treatment (deep ploughing + straw) could effectively improve soil compression-resilience characteristics.

     

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