Interactive Effects of Zinc Oxide Nanoparticles and Phosphorus on Wheat (Triticum aestivum L.) Grown Under Salt‐Affected Soil Conditions

ABSTRACT Aim The current study aimed to assess the potential of foliar‐applied zinc oxide nanoparticles (nZnO) in improving wheat growth and mitigating the zinc (Zn) deficiency stress that is increased by the negative interaction between Zn and phosphorus (P) under saline–sodic soil conditions. Methods A wire house trial was conducted to produce Zn‐enriched wheat grains following exposure to nZnO and to examine the interaction of applied Zn with the plant‐required P (PRP) (200 mg P kg −1 ). The treatments were: no nZnO and no P (control), no nZnO with PRP, nZnO‐primed seed with PRP, foliar application of nZnO with PRP, fertigation of nZnO with PRP, soil application of nZnO with PRP, and foliar and soil application of nZnO with PRP, designated as C, PRP, Seed‐nZnO+P, Foliar‐nZnO+P, Fertigation‐nZnO+P, Soil‐nZnO+P, and Foliar‐Soil‐nZnO+P, respectively. For each treatment, 100 mg L −1 Zn was used, except for Foliar‐Soil‐nZnO+P, for which 50 mg L −1 Zn solution was used during foliar application, and 50 mg kg −1 Zn was applied to the soil. Soil chemical parameters (pH s , EC e , sodium adsorption ratio [SAR], organic matter, soil Zn, and available P) were determined before the trial. Results The method of nZnO application influenced Zn–P interactions and affected the final Zn and P contents in soil, root, shoot, and grain of wheat. Foliar‐Soil‐nZnO+P showed optimum response compared to other amendments, having 11.8 mg kg −1 P and 6.93 mg kg −1 Zn concentration in soil. The maximum P concentration in root, shoot, and grain (3.1, 3.0, and 2.8 g kg −1 , respectively) and maximum Zn concentration in root, shoot, and grain (0.067, 0.055, and 0.030 g kg −1 , respectively) were found where Foliar‐Soil‐nZnO+P used in combination. Similarly, a 96% increase in grain weight pers pot was observed in Foliar‐Soil‐nZnO+P when compared with control. The application of Foliar‐Soil‐nZnO+P showed improved plant height (57%), spike length (44%), shoot dry weight (3.42 times), membrane stability index (99%), relative water content (39%), SPAD value (35%), photosynthetic rate (5.56 times), and transpiration rate (77%) compared with control. Conclusion Foliar and soil application of nZnO along with the PRP dose resulted in the least negative Zn–P interaction and optimal Zn concentrations in wheat grain and yield. These optimal results were attributed to rapid stomatal penetration of Zn via foliar application and minimum reaction time of soil‐applied nZnO, which minimized Zn–P complex formation. It is recommended that for Zn fertilization in salt‐affected soil, a combined foliar and soil application should be done to minimize negative Zn‐P interactions.