Consumer interest in food quality as it affects health has increased in recent years. Lycopene, the compound that imparts red color to watermelon, tomatoes, and some other fruits and vegetables, has been shown to reduce heart disease incidence and some cancers. The question of just how nutrient inputs impact lycopene in watermelons remains largely unanswered. The objectives of this study are to evaluate recommended, high, and low rates of potassium (K) and phosphorus (P) on the yield, quality, and composition of watermelons. Additionally, since nitrogen (N) is important in the general performance of P and K, N rate was included as part of the treatments.