After the rice harvest one can grow watermelons.Mounds are built and covered by agricultural plastic. Small holes are created in order to feed the watermelons. It takes 3 months to grow. For a field of 1000 m², seeds, fertilizers and insecticides represent an investment of 1 million đ. Watermelons will be sold at a price of 3500 đ/kg for a total profit of 6 million đ. For the same field, rice brings only 2 million đ in profit.