What progressive changes were taking place in the agriculture of Western European countries? Why was this transformation slow?

In England and Holland, new types of agricultural implements were used: light plow, seeder, thresher. A gradual transition from three-field to various types of crop rotation (grass-sowing, fruit-change) began.
After the era of the great geographical discoveries, new field and garden crops (corn, pumpkin, sunflower, potatoes, tomatoes, beans, tobacco) began to be mastered in Europe.
Serfdom in Western Europe in the XIV-XV centuries. almost disappeared. Some of the peasants managed to buy their plots from the lords.
The transformation was slow because the level of agricultural production was still low.