PROBLEM TO BE SOLVED: A crushing member can crush occluded soil as a barrier that blocks a flow path of an existing excavation groove to secure a flow path of the excavation groove, and it does not hinder drainage and drainage. The drainage function of can be reliably retained. SOLUTION: A crushing member 26 capable of crushing field soil is provided so as to be vertically swingable, and a closed soil DH generated at an intersection with an existing excavation groove WK by excavation of a plow member 11 or excavation by a plow member. The existing excavation due to the progressive formation of the above-mentioned excavation trench as closed soil in the existing excavation trench caused by the drop of the excavated soil D taken and discharged to the side into the existing excavation trench The crushing structure includes a crushing member that crushes the closed soil generated in the groove. [Selection diagram] Fig. 7【課題】圧潰部材は既存の掘取溝の流路を塞ぐ障壁としての閉塞土を圧潰して掘取溝の流路を確保することができ、水はけ排水性を妨げることがなくなり、掘取溝の排水機能を確実に保持することができる。【解決手段】圃場土を圧潰可能な圧潰部材２６を上下揺動自在に設け、すき部材１１の掘り取りによる既存の掘取溝ＷＫとの交差部分に生ずる閉塞土ＤＨ、あるいは、すき部材により掘り取られて側方に排出された掘取土Ｄの既存の掘取溝内への落ち込みにより生ずる既存の掘取溝内の閉塞土としての上記掘取溝の進行形成に起因して既存の掘取溝内に生起される閉塞土を圧潰部材により圧潰する圧潰構造を備えてなる。【選択図】図７
