The effect of phosphorus fertilizer under the influence of iron and zinc treatments on nutrient content and lettuce yield

Interaction between phosphorus (P), zinc (Zn), and iron (Fe) alters plant nutrient concentrations and nutritional quality. In this regard, there are a limited number of studies on P and micronutrient relations in lettuce plants. In this study, the effects of Zn and Fe applications on plant growth, concentrations, and contents of P, Zn, Fe, copper (Cu), and manganese (Mn) were determined in lettuce plants grown under increasing P rates. Lettuce plants grown under increasing P rates (0, 100, 200, and 400 mg kg-1 P) were treated with either sole or combined applications of 20 mg kg-1 Zn and 30 mg kg-1 Fe. Fresh and dry weights, P concentrations, and contents of lettuce were increased by P fertilization. With Zn and Fe applications, lettuce Fe contents were increased by medium P rates. Plant Zn contents were increased by P fertilization when the plant supplied Zn alone. Besides the highest P rate, Zn and Fe increased plant Zn content through P fertilization. Under no micronutrient condition, Cu concentration revealed insignificant changes, but its content was significantly increased by P application. Plant Mn concentration only increased by low P when the plant supplied Zn however Mn contents of lettuce were increased by P fertilization. In conclusion, even high P doses had no significant impact on Fe, Zn, Cu, and Mn concentrations in lettuce plants. Plant Zn concentrations increased when Zn was applied with Fe. Likewise, Cu increased but manganese declined. This emphasizes the importance of simultaneous Zn and Fe fertilizer application, especially in Zn biofortification research.