Three main criteria which should be considered while selecting the crops for rotation are -
Nutritional requirement - The plants should be selected in such a way that there nutritional requirements are different. This helps in avoiding competition between the two for nutrition.
Root pattern - The plants should be selected in a manner where one is deep rooted while the other is short rooted. This allows maximum utilisation of nutrients and avoiding competition.
Crop maturation - There should be a difference in the time of maturity of the two plants. One should mature earlier than the other.