The new strain grew easily and abundantly, producing a surplus that could be sold cheaply abroad. Ayutthaya, situated at the southern extremity of the floodplain, thus became the hub of economic activity. Under royal patronage, corvée labour dug canals on which rice was brought from the fields to the king's ships for export to China. In the process, the Chao Phraya Delta—-mud flats between the sea and firm land hitherto considered unsuitable for habitation—-was reclaimed and placed under cultivation. Traditionally the king had a duty to perform a religious ceremony blessing the rice plantation.[26]