The objective of the research was to investigate the effects of Potassium fertilizer, and Trichoderma harzianum and Interaction of the treatmen on Fusarium Wilt Tomato. The research was conducted from May to Oktober 2006, At The Green House and Laboratory Of Fitopatology Laboratory Sriwijaya University, Inderalaya. The research was Arranged in a Factorial Randomized Block Design. The First Fact…