Fig. 4 Observed and NLEAP-simulated residual soil NO^-₃–N (a) from the bottom of the root depth (BRD) to the maximum soil depth (BRD - 0.91 m) and (b) for the entire soil depth (0.0–0.91 m). Validation of the NLEAP 1.20 version for potato (P), lettuce (L), barley (B), and canola (CN) grown in the San Luis Valley