If rivers are not polluted and are allowed to flow in their own way, or sometimes allowed to flood the land, the land will become very fertile and able to produce all kinds of vegetables, trees and plants. The word rasa means taste. Actually all rasas are tastes within the earth, and as soon as seeds are sown in the ground, various trees sprout up to satisfy our different tastes. For instance, sugarcane provides its juices to satisfy our taste for sweetness, and oranges provide their juices to satisfy our taste for a mixture of the sour and the sweet. Similarly, there are pineapples and other fruits. At the same time, there are chilies to satisfy our taste for pungency. Although the earths ground is the same, different tastes arise due to different kinds of seeds. As Krsna says in Bhagavad-gita (7.10), bijam mam sarva-bhutanam: I am the original seed of all existences. Therefore all arrangements are there. And as stated in Isopanisad: purnam idam [Isopanisad, Invocation]. Complete arrangements for the production of all the necessities of life are made by the Supreme Personality of Godhead. People should therefore learn how to satisfy the yajna-purusa, Lord Visnu. Indeed, the living entitys prime business is to satisfy the Lord because the living entity is part and parcel of the Lord. Thus the whole system is so arranged that the living entity must do his duty as he is constitutionally made. Without doing so, all living entities must suffer. That is the law of nature.