Ratooning is done in case of few crops like sugarcane. It is a technique in which during harvesting bottom bits are left uncut to produce its ratoon or stubble crop.
Merits: The main benefit is that the crop matures much earlier and the other advantage is that it saves cost of preparing soil and planting.
Demerits: In sugarcane, ratooning leads to thinner canes with low sugar content. There is also an increased risk of pest attack.