2. Even without land rotation, the conditions required for weeds to grow are far lower than those of crops, that is, weeds require less soil than crops and consume less fertility. After they die, they can form new fertility in the field, and they consume more fertility than when they grow-in other words, the ups and downs of weeds are beneficial to soil fertility. Therefore, there is no need to be afraid of weeds in fallow farmland, which is good for restoring soil fertility.