Corn Steep Liquor Application Improves Pepper (Capsicum annum L.) Tolerance to Salinity

Salinity, caused by irrigation with water containing high salt concentrations, excessive fertilization, or the loss of leaching capacity in some soils, is a serious problem on a global scale. Its incidence leads to osmotic and specific effects, as well as an imbalance in nutrient uptake that hinders the growth of most crops. Biostimulants can improve salt tolerance by reducing the uptake and accumulation of toxic ions. Corn steep liquor (CSL) is a byproduct of corn cleaning and maceration. This study investigates whether CSL application induces adaptive responses in pepper (Capsicum annuum L.) plants cultivated under saline conditions. Four treatments were carried out with pepper plants in a culture chamber: irrigation with Hoagland nutrient solution; irrigation with 100 mM NaCl in the Hoagland nutrient solution; irrigation with 100 mM NaCl in the Hoagland nutrient solution and the foliar application of CSL at 5 mL L−1 every 7 days; and irrigation with 100 mM NaCl in the Hoagland nutrient solution and root application of CSL at 5 mL L−1 every 7 days. The beneficial effect of CSL in reducing the phytotoxicity of salt stress was found to be due to an improvement in the photosynthetic efficiency and a reduction in the generation of reactive oxygen species. Thus, the increase in MDA concentration due to saline treatment is less when applying CSL, which is 3.5 times less when it is performed via the foliar route and 4.6 times if the treatment is on the root. The results show that CSL application increased the aerial biomass and leaf area under saline conditions through physiological mechanisms that varied depending on the application method.