NCSWAP (nitrogen and carbon cycling in soil, water and plant) is a simulation model of the soil-crop-water system which integrates water flow dynamics, crop growth, N transformations, tillage and residue effects, soil temperature, and solute transport. A small plot field study was initiated in May of 1980 to determine the effects of N rate (2 or 20 g N/m2), tillage (rototill or no-till), and residue management system (residue return or noresidue) on soil parameters, and maize (Zea mays L.) production. Significant differences due to treatments (N rate, tillage, and residue) were not detected in 1981 for the measured soil-plant parameters including soil moisture, yield, and N uptake. Therefore, two representative treatment combinations (N rates of 2 or 20 g N/m2-tilled-no residue) characterized the field research data. Calculated and observed data sets were compared for several parameters including: (1) soluble NO3−N, (2) N leaching losses (3) plant total-N and15N, (4) root growth, (5) soil moisture, and (6) fertilizer efficiency. The objectives of this study were to initiate the validation process of the model NCSWAP, and to illustrate how NCSWAP can be used as a research tool to infer operational characteristics of the N cycle.