A subsoiler or flat lifter is a tractor-mounted farm implement used for deep tillage, loosening and breaking up soil at depths below the levels worked by moldboard ploughs, disc harrows, or rototillers. Most such tools will break up and turn over surface soil to a depth of 15–20 cm (6–8 in), whereas a subsoiler will break up and loosen soil to twice those depths. Typically a subsoiler mounted on a compact utility tractor will reach depths of about 30 cm (12 in) and typically have only one thin blade with a sharpened tip.
The subsoiler is a tillage tool which will improve growth in all crops where soil compaction is a problem. In agriculture angled wings are used to lift and shatter the hard pan that builds up due to compaction. The design provides deep tillage, loosening soil depth is deeper than a tiller or plough is capable of reaching. Agricultural subsoilers, according to the Unverferth Company, can disrupt hardpan ground down to 60 cm (24 in) depths. 
Various manufacturers' brochures claim that crops perform well during hot and dry seasons because roots penetrate soil layers deeper to reach moisture and nutrients. Brochures further claim that in wet conditions, the water passes more easily through the shattered areas, reducing the possibility of crops drowning.
Agricultural subsoiler implements will have multiple deeper reaching blades; each blade is called a scarifier or shank. Purdue University's Dept. of Agriculture indicates that common subsoilers for agricultural use are available with 3, 5 or 7 shanks. Subsoilers can be up to 15' wide, some models are towed behind tractors while others are mounted to the three-point hitch.
One type of subsoiler has a torpedo-shaped tip and is called a mole plough because the tip describes a path much like the burrow that a mole creates. Mole ploughs are used to create tile drainage, with or without tiles or tile line added. A form of this implement (with a single blade), a pipe-and-cable-laying plough, is used to lay buried cables or pipes, without the need to dig a deep trench and re-fill it.
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