Effects of partial root‐zone irrigation and nitrogen forms on the movement of nitrate in deep subsoil and its utilization by tomato plants

Abstract

AbstractThe fate of residual nitrogen (N) in specific soil layers under partial root‐zone irrigation (PRI) and fertilized with different N forms was studied using a soil column experiment with 15N‐labelled N (K15NO3) applied to 110‐cm‐deep soil layers. We found that alternate PRI (APRI) saved 34.3% more irrigation water but only decreased yield by an average of 6.2%, whereas fixed PRI (FPRI) and deficit irrigation (DI) reduced fruit yield by an average of 25.5 and 35.0%, respectively, compared to conventional sufficient irrigation (CI). Using the same irrigation mode, nitrate‐N application significantly promoted 15N‐utilization by the tomato fruit and crops for all irrigation modes. Compared to ammonium‐N application, nitrate‐N application increased the recovery rate of 15N‐labelled N in plants by 30.6% under CI, 14.3% under APRI, 22.8% under FPRI, and 10.6% under DI. The 15N accumulation peak was found at a depth of 40–60 cm, corresponding to an upward 15N migration distance of 65 cm for all treatments. However, a significant difference in the amount of residual N in the crop root zone (0–100 cm) was observed between CI and the other irrigation methods.Highlights Effects of PRI on the fate of residual nitrate studied with the15N tracer technique and simulated soil column. APRI could save 34.3% irrigation water without significant effects on tomato yield. Nitrate‐N application significantly promoted the growth of tomato. The residual nitrate in deep subsoil mainly moved upward under all irrigation modes.