Raising Tomato Tolerance to Soil Salinity via Foliar Application of Amino Acids and Soil Addition of Sulfur

Cultivating tomatoes in saline soils can be a viable strategy for enhancing agricultural production in Egypt while addressing the food gap and improving food security, provided that appropriate measures are taken. To evaluate this approach, a field trial was conducted over two consecutive seasons (2023/24 and 2024/25) using a split-split-plot experimental design to assess the performance of two tomato varieties, Florida and Alia, grown in saline soil with an EC of 6.25 dSm-1. The study examined the effects of soil application of elemental sulfur at rates of 0.0 and 300 kg fed-1 and foliar application of amino acids, including proline (60 mgL-1), methionine (60 mgL-1), and their combination (30 mgL-1 for each), alongside a control treatment. Various growth parameters, photosynthetic pigments, oxidative stress markers, fruit yield and quality were evaluated at different growth stages. The results indicated that the Florida variety exhibited greater tolerance to salinity than the Alia variety, leading to improved growth performance, fruit yield, and quality. The application of elemental sulfur significantly enhanced all studied traits, while among the foliar treatments, the combined application of proline and methionine was the most effective, followed by proline alone then methionine and the control, respectively. Overall, optimal performance and yield under saline conditions were achieved when tomato plants of the Florida variety were treated with elemental sulfur and foliar-sprayed with a combination of proline and methionine. The findings provide a future perspective on utilizing sulfur fertilization and foliar application of amino acids as an effective strategy to enhance tomato productivity in saline soils. This approach contributes to expanding agricultural land and promoting sustainable farming, particularly in salt-affected areas, with potential application to other crops to mitigate salinity stress challenges.