What is the plough that contains a strong triangular iron strip known as? 

A plough is a large farming tool with sharp blades that are attached to a tractor or animal and used to turn the soil over before planting.

A ploughshare is the strong triangular iron blade of the cutting or leading edge of a moldboard in a plough. It is used in agriculture to break and turn over the soil and uproots weeds.

Breaking up soil clumps improves soil structure, water and air penetration, and plant growth, resulting in higher yields.