Rice is an integral part of the Balinese culture. The rituals of the cycle of planting, maintaining, irrigating, and harvesting rice enrich the cultural life of Bali. At the beginning of planting time, after the water buffalloes walk the rice fields several times to prepare them, ceremonies are held to carry the young stems of rice that have been nurtured in a special nursery. On each section of the rice fields, the corner nearest to Gunung Agung receives the first young stems of rice. The planning and responsiblity of the irrigation and planting schedule are arranged through subak, a Balinese system that ties together rice cultivation with its water temple system. Historical evidence dates this system to around the 11th century, yet the yield per acre of a Balinese rice field is about the highest in the world.