<P> The three field system required more plowing of land and its introduction coincided with the adoption of the moldboard plow . These parallel developments worked hand in hand to increase the productivity of the land . The legume crop needed summer rain to succeed, and so the three - field system was less successful around the Mediterranean . Oats for horse food could also be planted in the spring, which, combined with the adoption of horse collars and horseshoes, led to the replacement of oxen by horses for many farming tasks, with a concomitant increase in agricultural productivity and the nutrition available to the population . </P> <P> One of the first Germans to question this system, and new ways of expanding beyond this medieval system was Johann Friedrich Mayer, in his 1769 work Lehre vom Gyps als vorzueglich guten Dung zu allen Erd - Gewaechsen auf Aeckern und Wiesen, Hopfen - und Weinbergen . </P>

What was the effect of the three field system