ABSTRACT Nutrient recycling and mineral balance are important factors affecting nutrient budgets in oil palm (Elaeis guineensis Jacq.) plantations. The nutrient budget includes processes such as plant uptake, removal by harvesting, accumulation or storage in the standing plant, and recycling through decomposition of cover crop Asystasia gangetica (L.) T. Anderson can be utilized as cover crops in mature oil palm plantations with appropriate management. This study aimed to examine the growth of A. gangetica in 17 yr old oil palm plantations with different populations, understanding the contribution of A. gangetica to improve available nutrient in the plantation on the nutrient balance, and to study its role as cover crop in the mature oil palm plantation. The experiment was conducted in an experiment field of 17 yr old of mature oil palm at Bogor, Indonesia. Results showed that A. gangetica can be used as cover crops in mature oil palm plantations because it meets several conditions such as rapidly covering the land (11 wk after planting), and able to increase the available N, P, K as much as 18.49%, 9.20%, 38.36%, respectively, based on the nutrient balance with the optimum population is 1 000 000 plants ha-1