First, we should note that these innovations took place at different times. Crop rotation, also known as the three field system, was introduced during the Middle Ages, sometime after 1000 AD. This helped cause an agricultural revolution because it increased crop yields. By planting different crops in a given field each year (or allowing it to lie fallow), farmers prevented the depletion of nutrients in the soil. In addition, the use of this system meant that 2/3 of the land rather than 1/2 would be cultivated each year.
The enclosure system did not become common until the 1500s. This system took away the peasants' right to work a certain amount of land on their own. Instead, the person who owned the land would enclose it, make it in to one plot, and often raise sheep on it. This led to more efficient use of the land, which helped to increase yields. Land would now be farmed as one big plot instead of as many little ones with wasted space in between.
Both of these changes, though separated by centuries in time, helped to increase agricultural yields. This increase can be seen as an "agricultural revolution."