<P> This is a variety of ridge plough notable in that the blade points towards the operator . It is used solely by human effort rather than with animal or machine assistance, and is pulled backwards by the operator, requiring great physical effort . It is particularly used for second breaking of ground, and for potato planting . It is found in Shetland, some western crofts and more rarely Central Scotland . The tool is typically found on small holdings too small or poor to merit use of animals . </P> <P> The mole plough allows underdrainage to be installed without trenches, or it breaks up deep impermeable soil layers that impede drainage . It is a very deep plough, with a torpedo - shaped or wedge - shaped tip, and a narrow blade connecting this to the body . When dragged through the ground, it leaves a channel deep under the ground, and this acts as a drain . Modern mole ploughs may also bury a flexible perforated plastic drain pipe as they go, making a more permanent drain--or they may be used to lay pipes for water supply or other purposes . Similar machines, so called pipe - and - cable - laying ploughs, are even used under the sea, for the laying of cables, as well as preparing the earth for side - scan sonar in a process used in oil exploration . </P> <P> Heavy land requires draining to reduce its water content to a level satisfactory for efficient plant growth . Heavy soils usually have a system of permanent drains using either perforated plastic or clay pipes which discharge into a ditch . Mole ploughs are used to form small tunnels (mole drains) in the soil at a depth of up to 950 mm (30 in) at an angle to the pipe drains . Water from the mole drains seeps into the pipes and runs along them into a ditch . </P> <P> The mole plow allows underdrainage to be installed without trenches, or it breaks up deep impermeable soil layers which impede drainage . It is a very deep plow, with a torpedo - shaped or wedge - shaped tip, and a narrow blade connecting this to the body . When dragged through the ground, it leaves a channel deep under the ground, and this acts as a drain . Modern mole plow may also bury a flexible perforated plastic drain pipe as they go, making a more permanent drain--or they may be used to lay pipes for water supply or other purposes . A simple check can be made to find if the subsoil is in the right condition for mole ploughing . Compact a tennis ball sized sample taken at moling depth by hand, then push a pencil through . If the hole remains intact without splitting the ball the soil is in an ideal condition for the mole plough . </P>

Who invented a plow with an iron blade that was strong enough to till the soil of the great plains