Nitrate fertilization dramatically reshapes the soil microbiome around cucumber roots, recruiting beneficial Funneliformis fungi while stimulating plants to produce resveratrol, a potent antifungal compound. Split-root experiments demonstrated that nitrate specifically triggered resveratrol accumulation and enriched protective fungal communities, creating a natural defense system against Fusarium wilt. Conversely, ammonium fertilization had the opposite effect, promoting pathogenic fungi and increasing plant susceptibility to disease. This finding illuminates a sophisticated three-way interaction between nitrogen chemistry, soil ecology, and plant biochemistry that determines disease outcomes. The research suggests that strategic fertilizer choice could replace fungicide applications in agriculture, offering a more sustainable approach to crop protection. For human health applications, this work reinforces resveratrol's antimicrobial properties and suggests that dietary nitrates might influence our own microbiome composition. However, the study was conducted in controlled laboratory conditions with a single crop species, so field validation across diverse agricultural systems remains necessary. The discovery represents a significant advance in understanding how nutrient management can harness natural plant defense mechanisms.