SUMMARY
ABSTRACTTo support Indonesian organic agricultural system that will be started in 2010, fertilizing will be done with organic fertilizer. The function of fertilizer is to fulfill the plant nutrition. The needs of nutrition is different from plant to plant so it is necessary to formulate the organic fertilizer to balance the nutrition. The most needed nutrition for plant consists of N, P and K. The formulated organic fertilizer were applied for mango, chili, rose, paddy, oil palm, and ginger.Materials which were used to formulate organic fertilizer were compost (X1), cow manure (X2), rock phosphate (X3), and chaff ash (X4). Method which was used for formulated organic fertilizer was linear programming (LP). The objective function was to minimize the cost that was based on each material cost. The constrain function in the left side was content of N, P and K dry basis for each material while in the right side was the needs of plant’s N, P, and K nutrition per hectare.The result of problem solving with LINDO program was : 4 898.00 kg/ha X1, 2 367.60 kg/ha X2 and 1 808.89 kg/ha X3 for mango’s formula; 5 296.08 kg/ha X1, 1 465.70 kg/ha X2 and 4 325.93 kg/ha X3 for chili’s formula; 7 450.14 kg/ha X1, 6 462.52 kg/ha X3 and 1 045.98 kg/ha X4 for rose’s formula; 5 088.26 kg/ha X1, 744.28 kg/ha X3 and 1 725.96 kg/ha X4 for paddy’s formula; 2 943.88 kg/ha X1, 4 646.32 kg/ha X3 and 6 520.57 kg/ha X4 for oil palm’s formula; 23 631.42 kg/ha X1, 19 311.75 kg/ha X3 and 2 479.06 kg/ha X4 for ginger’s formula.The NPK content of the formulated organic fertilizer can be determined with mathematic calculation, but to determine the real NPK content must be tested in laboratory. The result of NPK content by calculating and the result from laboratory test have relatively small differences, that is about 0% to 8.33%.Key word : organic fertilizer, compost, plant nutrition, linear programming