4. Correlation Study of Soil-P Test for Vegetables Grown in the Ultisols at Nanggung, Bogor, Juang G. Kartika and Anas D. Susila 1 Abstract Phosphorus (P) correlation experiment has been done in Ultisols in Nanggung District, Bogor, Indonesia from 2006-2007 to find the best P ext Taction method suitable for vegetables i.e. amaranth (Amaranthus sp.), kangkung (Ipomoea aquatica L.), eggplant (Solanum melongena LJ, chili (Capsicum annuum L.), tomato (Lycopersicon esculentum Mill), green bean (Pahaseolus vulgaris L.) and yard-long bean (Vigna unguiculata L.). Treatments were Prate: 0, 45, 90, 135 and 180 kg/ha P20 S equal to 0, 125, 250, 375 and 500 kg/ha SP36 (36% P20 S). Treatments were arranged in Randomized Complete Block design with three replications. Soil samples were taken from every plot and analyzed with five extraction methods (25% HCI, Morgan Vanema, Bray-I, Mehlich and Olsen). Soil analysis results were correlated with the relative yield of each vegetable. The best soil extraction method is that which showed highest correlation with vegetable relative yield. Olsen method showed highest correlation with amaranth, chili and tomato relative yield; 25% HCL with yard-long bean and eggplant; and Morgan Vanema kangkung relative yield and Bray-l for green bean. Keywords: Vegetables, P-correlation, relative yield, Ultisols. 1. Introduction Phosphorus (P) is the macro nutrient for plants; and next to nitrogen, is the second highest needed by plants. P nutrients have a role in carbohydrate, fat and protein metabolism. Phosphorus acts as intermediary, to keep and supply energy for me- tabolism like respiration and fermentation (Soepardi, 1983). P also arranges enzy- matic process, closely related to compilation of crop essentials like nucleic acid at cell core; increases resilience to disease and increases crop quality. Sufficient amounts of available P can increase root development, assist in flower initiation and other reproductive organs and quickens ripening process of fruit (Nyakpa et aI., 1988; Rosmarkam and Yuwono, 2002). Addition ofP into the soil can increase production and dry matter of the plant. P nutrients in plant also helps reduce nitrogen stimulating fungus effect. I Plant Production Division, Department of Agronomy and Horticulture, Faculty of Agriculture, Bogor Agricultural University, JI. Meranti, Komplek IPB Darmaga, Bogor 16680, Indonesia. ikajuang@yahoo.com, anasdsusila@ipb.ac.id, Te1lFax: 0251 629353 65