## 6 Significance of Chemical and Biological Agents Encapsulation in Sustainable Agriculture  
When aiming to achieve a high-quality crop, balanced nutrition, and fertilization are essential. Chemical agents (i.e., Ca\({}^{2+}\), Cu\({}^{2+}\), Mg\({}^{2+}\)) are essential plant nutrients and play important roles in many biochemical pathways. They are essential in the structure and permeability of cell membranes, plant cell division, and elongation. They act as signaling ions in the regulation of biochemical cascades [17]. For example, Ca\({}^{2+}\) has a signaling role in the upregulation of genes responsible for synthesizing polyphenic compounds [20]. On the other hand, Ca\({}^{2+}\) is often found in soil, but the biggest problem is, its prevalent form is relatively insoluble, like CaCO\({}_{3}\). Cu\({}^{2+}\) also show a stimulating effect on the production of plant secondary metabolites and is essential for some biochemical and physiological pathways, but the problem is that at higher concentration becomes toxic [31]. Mg\({}^{2+}\) is tightly connected to the photosynthesis process as it is the central atom of the chlorophyll molecule. Mg\({}^{2+}\) becomes extremely phytotoxic when concentrations of Ca\({}^{2+}\) in plants are low [106; 107] because Ca\({}^{2+}\) ions control and modify the uptake of available Mg\({}^{2+}\)[108]. It is important to develop products that will have nutrients in bioavailable form. Furthermore,exact concentrations for relatively toxic agents should be regulated more carefully. Thus, control of the dosage to minimize its release into the environment is crucial. Encapsulation into biopolymeric microparticles is one of the ways which can mend these problems. _Trichoderma viride_ (Figure 3) is a biological control agent used in agriculture as biostimulants and against phytopathogens. Generally, _Trichoderma_ spp. are used in agriculture because of their ability to produce a relatively high quantity of specific enzymes [109], and secondary metabolites to control phytopathogens [110]. Mycoplasma _Trichoderma_ spp. produce antimicrobial compounds [111], has antibiosis activity, and induces resistance of the host plant [111, 112]. As mentioned above, _Trichoderma_ spp. produces hydrolytic enzyme complex, which is made of chitinases, \(\beta\)-glucanases, cellulases, and proteases. These enzymes, especially chitinases, which are the most effective, help in the decomposition of the cell walls of phytopathogens, allowing _Trichoderma_ spp. hyphae penetration, colonization, and mycoparasitic activity to occur [110, 113, 114]. _Trichoderma_ species are also known to acidify their surrounding environment via the secretion of organic acids and can solubilize some chemical agents [115]. Recently authors [110] reported the protection of encapsulated fungus _Trichoderma harzianum_ against ultraviolet radiation. Furthermore, encapsulation improved chitinolytic and cellulosic activity of the fungus and greater control of _Sclerotinia scleroorum_ (white mold), a well-known phytopathogen. [PERSON] et al. [69] report a simple and innovative way to encapsulate _Bacillus salmonaya_, a plant growth-promoting rhizobacteria. Successful protection of bacteria was achieved with encapsulation in degradable chitosan/alginate microparticles. The bioactivity of bacteria was maintained in samples that were encapsulated. The application of alginate/chitosan-based particles in agriculture is becoming more popular because of their abundance, relatively low price, and because they are rich in amino and hydroxyl groups. For example, chitosan has been successfully utilized for delivering fertilizers, pesticides, and nutrients, and it found its application as an adsorbent in wastewater treatment [116, 117, 118, 61]. Alginate-based microparticles are lately becoming increasingly popular, and in Table 1, the most recent examples of fungal biocontrol agents encapsulation are presented.