Sustainable Management of Salinity Stress: Biostimulant Effects on Tomato Roots and Soil Health

Soil salinization, intensified by climate change, reduces soil quality and crop yields, posing a severe threat to food security. The present study focuses on the effects of two doses of a biostimulant, based on plant protein hydrolysates, on improving the root system and the quality of NaCl-affected soil. For this purpose, several experiments were conducted on Solanum lycopersicum plants that were grown for 60 days under four salinity conditions, obtained by combining two salinity levels and two irrigation water types (a total of 36 treatments). Several physical and chemical soil properties and root characteristics were evaluated, and it was shown that the application of the biostimulant (BALOX ® ) significantly increased root length and total root area, even under high salinity conditions. An increase of up to 70% over the control was achieved, mostly in roots smaller than 2 mm in diameter, which are primarily responsible for nutrient absorption. It was also revealed that BALOX ® ’s interaction with the root system favorably influenced soil properties, particularly Cation Exchange Capacity (CEC). Likewise, the Aggregate stability (AS) increased up to 36%, and the percentage of organic matter (OM) up to 6.4%. The CEC increased by 66–72% with the biostimulant application, and there were reductions in soil salinity and Na + and Cl − concentrations (20%, 19%, and 24%, respectively). In addition, BALOX increased the area and length of fine roots, thereby expanding the rhizosphere and enhancing its interaction with the soil. The use of the biostimulant may help prevent soil degradation and contribute to tomato plants’ tolerance mechanisms under salt stress.