Fig. 2. Flow-weighted nitrate N concentration in subsurface tile drainage as affected by time of N application and nitrapyrin (NP) for corn in four cycles of a corn–soybean rotation for (a) corn grown in even years (1990 and 1992) and (b) corn grown in odd years (1991 and 1993). All months shown had drainage exceeding 10 mm. Vertical bars above each monthly data set indicate the LSD (0.10). Absence of vertical bars above a monthly data set indicates no significant difference among flow-weighted nitrate N concentrations.