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.