Crop sequence is one of those agriculture practices in which allelopathic activities among plant species could be enhanced. In this work, peanut (Arachis hypogaea L.) in addition to its pathogens and soil microorganisms were exposed to the allelochemicals derived from its preceding crops during the crop sequence, i.e. garlic, onion, barley and canola. Several solvent extracts of preceding crops showed varied antifungal activity against the tested pathogens in vitro. For this target field experiment was conducted at Nubaria province, during 2009 summer season, where peanut root- and pod-rots are epidemic. Root- and pod-rot diseases of peanut caused by Aspergillus niger Vantighn and Fusarium oxysporum Schlecht are the most serious diseases affecting peanut productivity. All preceding crops significantly reduced root- and pod-rots of peanut which effected by increasing of soil phenols content. Garlic was the best preceding crop significantly reduced the two diseases. The combination of garlic as a preceding crop and its residues induced root- and pod-rot incidence reduction by 86.8% and 50.4%, respectively, compared to without residues which gave reduction by 79.8% and 45.2% for both diseases. All preceding crops significantly increased growth characters, microbial counts, N2 fixation bacteria, phosphate dissolving bacteria, VAM mycorrhiza and yield of peanut, canola was the most effective.