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To elucidate the impact of fertilizer nitrogen (N) practices upon water quality in Lake Bloomington watershed, a 74 ha site has been subdivided into six equal parcels of approximately 12.3 ha. Within each 12.3 ha parcel, 10 cm tile was installed on a 22.8 m grid with interceptor access to collect tile water on a weekly basis for nitrate-N concentration. Six agricultural fertilizer N practices for corn were evaluated to determine if the timing, rate, or form of N can reduce nitrate-N release into tile water. In general, the application of anhydrous ammonia in the spring produced equivalent grain yields to that of the fall-applied treatments, while reducing nitrate-N release into tile water. This reduction could be due to many factors, one of which was the increased plant N accumulation of the spring-applied treatment. Thus, one method to reduce nitrate-N of water entering Lake Bloomington, IL is to encourage the application of fertilizer N in the spring. The knowledge gained from this study will aid in developing recommendations that deal with fertility and cultural practices that promote the safe stewardship of Illinois farmland, while maintaining high quality drinking water.