The soil is a biodegradable material, and SeNPs are used to stimulate the soil organic matter. It has been shown that the humic substance, which is delivered synchronously with SeNPs and other NPs, handles the stimulation effect as well
[20]. Microbial communities control organic matter degradation, which has a significant impact on soil fertility. Within specific environments, bacteria are not a faceless mixture of once-gained participants, but a structured, strictly-ordered polymicrobial community in which each participant has a specific functional role. As a bioreactor, the soil speeds up a wide range of biodegradation processes
[21]. In terms of biological processes and yield in the soil and plants, the application of Se in standard fertilizer form is deemed less efficient than the application of SeNPs in standard fertilizer form
[22]. Specifically, it has been found that Se can ease stress in plants because it causes the manufacture of secondary metabolites and increases the activities of antioxidant enzymes according to the literature
[17]. To mitigate multiple kinds of abiotic stress, including extremely high temperatures, droughts, heavy metal accumulation, and salt, the usage of SeNPs is increasingly popular and is becoming increasingly important. The bean plant is used for soil fertility analysis, which enhances plant development. The plant has been evaluated and analyzed for chlorophyll and protein content. Plants showed effective growth at high concentrations of SeNPs
[23]. A study by Hebat-Allah et al. (2019) showed that SeNPs impacted the growth of groundnut cultivars by altering photosynthetic pigments, lipid peroxidation, antioxidant enzymes (ascorbic acid peroxidase, catalase, peroxidase), total soluble sugars, phenol content, and total flavonoids in the plants. Tolerance to sandy soil conditions was improved when SeNPs were used as a stimulant and/or a stressor
[24]. As an example, handling with SeNPs at a ratio of 100 mg/L in barley (
Hordeum vulgare) crops cultivated under saline stress led to a direct accumulation of Se in leaves, an improvement in the amount of aggregate phenolic composites, and a decrease in the content of ROS-mediated cellular membrane harm markers, including such MDA, which may affect metabolism and be responsible for nutrient deficiencies
[25]. In the study conducted on tobacco plants it was shown that SeNPs had no positive effect on the number of tobacco shoots, whereas 50 mg L
−1 selenate completely inhibited the expansion of tobacco shoots. Increasing the concentrations of SeNPs significantly increased the rate of roots regeneration. With the use of 50–100 mg L
−1 SeNPs, the roots were far more extensive and densely packed, and the fresh weight increased significantly as well. On the contrary, selenate completely inhibited the formation of roots at concentrations ranging from 50 to 100 mg L
−1 [24]. In plant tissue culture, the biological activities of SeNPs were distinct from those of the selenate ion (SeO
32-). It was showed that SeNPs concentrations ranging from 50 to 100 mg kg
−1 significantly increased organogenesis and root system growth (>40%), whereas selenate had no such effects at any intensity. SeNPs concentration ranging from 50 to 100 mg kg
−1 strongly prevented both callus development and root regeneration. This previous concentration was effective in stimulating not only roots initiation or roots elongation, but biomass production as well
[24].