Soil improvement method and underground trench construction and deep scarification all-in-one machine thereof

The invention discloses a soil improvement method and an underground trench construction and deep scarification all-in-one machine thereof, and belongs to the technical field of soil improvement, and the soil improvement method comprises the following steps: cutting soil, and backfilling a cutting seam under the extrusion of soil on two sides of the cutting seam to form a scarification structural seam; grooves are constructed in the bottom end of the soil loosening structural seam, the grooves are arranged in parallel at intervals and communicate with the soil loosening structural seam, the soil loosening structural seam forms a vertically-communicated water seepage channel, and the grooves form a containing cavity; salt in the soil is downwards conveyed to the containing cavity through the water seepage channel, and the salt content in the soil is reduced; nutrients of the soil surface layer are downwards conveyed to the containing cavity through the water seepage channel, and loss of the nutrients on the so