The development of a three-field rotation system for planting crops[AA] increased the usage of land from one half in use each year under the old two-field system to two-thirds under the new system, with a consequent increase in production. The development of the heavy plough allowed heavier soils to be farmed more efficiently, aided by the spread of <answer>the horse collar</answer>, which led to the use of draught horses in place of oxen. Horses are faster than oxen and require less pasture, factors that aided the implementation of the three-field system.
What invention allowed horses rather than oxen to be used to plow?
the horse collar