LAMAR, JHOANNA M. 2014 LAMAR, JHOANNA M. 2014. EFFECT OF DIFFERENT LEVELS OF ORGANIC FERTILIZER ON SWEET TAMARIND (Tamarindus indica Linn.) PRODUCTIONIN RELATION TO SOIL MICROBIAL POPULATION AND INSECT PESTS AND DISEASES INCIDENCE . Agricultural College, Magalang, Pampanga Pampanga. Adviser: Janette B. Musni, MSA The study was conducted to determine the effect of different levels of organic fertilizer on sweet tamarind (Tamarindus indica lL.) production in relation to _ soil Microbial population and insect pests and diseases incidence for October 2013 to March 2014. The sweet tamarind "aglibut" variety was subjected to different treatments namely:T;control (without fertilizer), Teo-50% lower than recommended rate (RR) of organic fertilizer based on soil analysis, T3100% of organic fertilizer as RR based on soil analysis, and T,50% more than RR of inorganic fertilizer. The experimental design followed is Complete Randomized Designed (CRD) with three replications. The result of the study showed that the different level of organic fertilizer applied has an effect in the soil microbial population but did not affect the incidence of insect pests and diseases. As the regard of the length, width, thick, treatment 4 has the largest mean while treatment 3 has the Indeed, the that the effect of different levels of organic fertilizer on the sweet tamarind by using "Aglibut Sweet" variety were found similar and has no significant.