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In an effort to a investigate practical method to minimize NO3 - leaching while maximizing N removal in land application of animal manure, an experiment was conducted in a greenhouse using perennial ryegrass (Lolium perenne L.) for its ability to maintain a relatively high ratio of NH4 + to NO3 - in soil and high rate of N uptake. Corn silage (Zea mays L.) grown under similar conditions using the same soil was used for reference comparison to observe the different impacts of ryegrass and silage on NO3 - concentration in leachate. The experimental design consisted of seven N application rates (0, 200, 400, 600, 900, 1500 and 2100 kg N /ha/yr) for the ryegrass and four N application rates (0, 200, 400 and 600 kg N /ha/growth) for corn silage. Each treatment of the two crops had three replications. The source of N was dairy manure with 71% to 76% of TKN being ammoniacal N (TAN). The average NO3 - concentration in the leachate from ryegrass ranged from 0.34 to 3.49 mg N/L for the N application rates. However, the average NO3 - concentration in the leachate from silage was 0.66, 0.22, 3.67 and 26.8 mg N/L respectively at the four N application rates. Therefore the NO3 - concentration from the leachate of ryegrass at 2100 kg N/ha application rate was only 13% of that from the leachate of silage at 600 kg N/ha application rate. The primary reasons for this great difference included that ryegrass had the ability to maintain a relatively lower ratio of NO3 - to NH4 + in soil, and higher N uptake. The results indicated that the goal of enhancing N application rate under the restraint of reducing NO3 - leaching to an acceptable level could be realized in land application for treating animal manure.