From the 16th century onward, Aceh increased the production of pepper, an important export commodity, in exchange for rice, which grew well in the Batak wetlands. Batak people in different areas cultivated either "sawah" (wet rice fields) or "ladang" (dry rice), and the Toba Batak, most expert in agriculture, must have migrated to meet demand in new areas. The increasing importance of rice had religious significance, which increased the power of the Batak high priests, who had responsibility for ensuring agricultural success.