Fertigation of NaCl-stressed lentil and soybean plants with silica nanoparticles improves seed yield and nutritional attributes

Lentil (Lens culinaris) and soybean (Glycine max) are proteinaceous legumes susceptible to salinity stress. This study aimed to evaluate the fertigating potential of silica nanoparticles (SiNPs) in improving the physiochemical status, yield parameters, and seed nutritional qualities of the legumes exposed to salinity stress. Characterization of the synthesized SiNPs revealed amorphous, round-shaped particles, a size of 15–40 nm, and a surface charge of −6.18 mV. Different concentrations of SiNPs (0, 1, 5, 10 g/L) were applied to the plants in combination with four different concentrations of NaCl (0, 200, 400, 600 mM) during the reproductive phase of plants. The results indicated that the SiNPs (especially 10 g/L) efficiently reduced the negative impacts of salinity by improving the physiochemical parameters (growth, pigments, primary metabolites, antioxidant enzymes). Similarly, the improvement in yield parameters (pods per plant, pod length, seeds/10 pods, etc.) and seed nutritional attributes (protein, sugar, free amino acids, free fatty acid, polyphenol contents, etc.) were observed irrespective of the NaCl concentrations. Specifically, applying 10 g/L SiNPs enhanced the total pod numbers by 1.70, and 1.57 folds; and the total number of seeds/10 pods by 1.44, and 1.65 in lentil and soybean plants, respectively, compared to the control set (600 mM NaCl). Moreover, the seed protein content was augmented by 3.29, and 1.30 folds compared to the 600 mM NaCl stressed plants (lentil and soybean, respectively) when treated with 10 g/L SiNPs. Therefore, it can be concluded that SiNPs can be used sustainably to improve yield and nutritional attributes under stressed conditions.