Zinc biofortification of lettuce using environmentally friendly zinc sources in an acidic soil

• Glycine treatment in acidic soil has a stimulating effect on lettuce crop. • Zn mobility between mature and young leaves depends on Zn treatment. • Soil application of sustainable chelates for high-efficiency Zn biofortification. The application of micronutrients to deficient agricultural soils using environmentally friendly chelates is essential for sustainable agriculture. This paper explores the ability to increase the Zinc (Zn) level in the edible part of lettuce ( Lactuca sativa L.) crop by applying non-traditional Zn sources. For this purpose, Zn-citric (Zn-CIT) and Zn-glycine (Zn-GLY) complexes were applied to an acidic agricultural soil (dose of 8 mg Zn kg -1 soil). The effects were compared with a treatment of ZnSO 4 , the source traditionally used to supply this micronutrient. The influence of Zn-CIT, Zn-GLY and ZnSO 4 treatments on different plant and soil parameters after lettuce cultivation was studied. The experimental results showed that the application of Zn-CIT and Zn-GLY to the selected acid soil produced a biofortification efficiency in the edible part of the crop, with increases in Zn concentration of 119% and 148% for Zn-CIT and Zn-GLY in young leaves or 337% and 479% for Zn-CIT and Zn-GLY in mature leaves, with respect to the control. Otherwise, the mobility patterns of Zn within the plant and from the soil to the plant depended on the treatment applied. The glycine treatment showed a stimulating effect on the crop, specifically on yield, morphometric parameters and Zn translocation between mature and young leaves (increases of 21%, 9% and 33% in yield, stem diameter and Zn translocation respectively, with respect to the control). However, the positive effect of the Zn-GLY treatment was not due to a synergistic effect of Zn 2+ and glycine application. The use of Zn-glycine in this acid soil is highly recommended as an environmentally friendly zinc source to achieve adequate biofortification in lettuce plants, allowing subsequent cultivation without additional Zn supplementation.