This study focuses on how to determine secondary plants at smallholdings oil palm plantation at Langkat regency, North Sumatra province of Indonesia. This research is motivated by the fact that there is a change of land use in Langkat, from paddy field to oil palm plantation. The situation has caused job loss in the agriculture sector. In the oil palm plantation, however, there is empty space in the beginning of the planting period due to the nature of oil palm plantation itself. The space can be used for secondary plants (such as horticulture plants), which have competitive prices and high productivities. We use linear programming model to formulate the problem of selecting horticulture plants to cultivate in smallholdings oil palm plantation. The model is solved using MS Excel Solver, and the results show that cayenne pepper (cabai rawit) and long bean (kacang panjang) are selected as the optimum secondary plants to plant.

Key words: Cultivation planning, linear programming, land diversification, oil palm plantation