A simple and inexpensive leaf spray could help tomato plants grow better in salty soils, offering farmers a promising new way to protect crops as farmland becomes increasingly affected by salt.
The new research, led by scientists at The University of Texas at El Paso (UTEP), suggests the treatment could improve crop production in regions where soil salinity is making farming more difficult.
The study, published in the International Journal of Phytoremediation, focuses on a practical solution that is easy to apply and uses only small amounts of natural and environmentally friendly materials.
Soil salinity is becoming a growing problem around the world. When too much salt builds up in the soil, plant roots struggle to absorb enough water, even when moisture is available.
High salt levels can also become toxic, damaging plant cells, reducing nutrient uptake, slowing photosynthesis, and lowering crop yields. In many cases, land that was once productive becomes much harder to farm.
Researchers estimate that salty soils now affect more than 3.2 million square miles (8.3 million square kilometers) of land worldwide, an area roughly the size of Australia or Brazil. The problem is especially serious in dry and semi-dry regions and threatens between 20% and 30% of the world’s irrigated farmland.
Tomatoes are one of the world’s most important vegetable crops. Global production reached about 192 million tons in 2023, making even small improvements in salt tolerance valuable for farmers and food supplies.
The research team developed a leaf spray made from two main ingredients. One is manganese oxide nanoparticles, tiny particles that help support important plant processes. The other is chitosan, a natural substance made from the shells of shrimp, crabs, and other crustaceans. Instead of treating the soil, the solution is sprayed directly onto the leaves, allowing the plants to strengthen their own natural defense systems.
According to the researchers, the treatment does not remove salt from the soil. Instead, it helps plants cope with the stressful conditions, allowing them to continue growing even when salt levels are high.
The scientists tested the spray on tomato plants grown in greenhouse conditions under both moderate and severe salt stress. The results were encouraging. Under the highest salt levels, plants treated with the spray produced shoots that weighed about twice as much as untreated plants. Their root weight also increased by more than 55%, giving them a stronger foundation for absorbing water and nutrients.
The treatment also improved the plants’ ability to carry out photosynthesis. Levels of carotenoids—important pigments that help capture sunlight and protect plant cells—increased by about 91%. At the same time, the spray reduced signs of damage inside plant cells caused by salt stress.
Another important finding involved the plants’ natural antioxidant defenses. Antioxidant enzymes, which protect cells from harmful molecules produced during stress, became much more active after treatment. In some cases, enzyme activity increased by as much as 300%, helping the tomato plants better defend themselves against harsh growing conditions.
The researchers believe one of the biggest advantages of the spray is its simplicity. It uses inexpensive ingredients, requires only very small doses, and works by boosting the plant’s own protective systems rather than trying to remove salt from the environment.
Although the findings are promising, the scientists emphasize that the study was conducted in a greenhouse. Larger field trials are still needed to determine how well the treatment performs under real farming conditions, where weather, soil differences, and other environmental factors can affect crop growth.
Future research will also examine whether repeated use of the spray has any long-term effects on soil health or the surrounding environment.
Even so, the researchers believe this low-cost, environmentally friendly approach could become an important tool for helping farmers maintain crop production on land increasingly affected by soil salinity, supporting food security as climate and environmental challenges continue to grow.
