Hydrogel Alginate Seed Coating as an Innovative Method for Delivering Nutrients at the Early Stages of Plant Growth

Abstract

Seed coating containing fertilizer nutrients and plant growth biostimulants is an innovative technique for precision agriculture. Nutrient delivery can also be conducted through multilayer seed coating. For this purpose, sodium alginate with NPK, which was selected in a preliminary selection study, crosslinked with divalent ions (Cu(II), Mn(II), Zn(II)) as a source of fertilizer micronutrients, was used to produce seed coating. The seeds were additionally coated with a solution containing amino acids derived from high-protein material. Amino acids can be obtained by alkaline hydrolysis of mealworm larvae (Gly 71.2 ± 0.6 mM, Glu 55.8 ± 1.3 mM, Pro 48.8 ± 1.5 mM, Ser 31.4 ± 1.5 mM). The formulations were applied in different doses per 100 g of seeds: 35 mL, 70 mL, 105 mL, and 140 mL. SEM-EDX surface analysis showed that 70 mL of formulation/100 g of seeds formed a continuity of coatings but did not result in a uniform distribution of components on the surface. Extraction tests proved simultaneous low leaching of nutrients into water (max. 10%), showing a slow release pattern. There occurred high bioavailability of fertilizer nutrients (even up to 100%). Pot tests on cucumbers (Cornichon de Paris) confirmed the new method’s effectiveness, yielding a 50% higher fresh sprout weight and four times greater root length than uncoated seeds. Seed coating with hydrogel has a high potential for commercial application, stimulating the early growth of plants and thus leading to higher crop yields.

Superabsorbent Polymer Hydrogels for Sustainable Agriculture: A Review

“…It is important to choose solutions capable of dealing with a variety of different futures. The most viable mitigation strategies for climate change in water-stressed areas appear to be the prevalent use of irrigation (including improved varieties of irrigation), an increase in irrigation efficiency and development, as well as water and soil conservation techniques and technologies [27,28].…”

“…In addition, coated seeds can be kept for extended periods without a deterioration in quality. These seeds can be produced by soaking them in solutions containing the necessary components, such as micronutrients, and then drying them or putting them through the process of germination directly [27]. The materials that are utilised for coating make it possible to adhere biological or chemical substances to the surface of the seed.…”

“…The carrier can be an adhesive (such as xanthan gum or arabic gum), a filler (such as charcoal, lime, or peat), a polymer (such as derivatives of cellulose), or a polysaccharide (chitosan, alginate). The design of the seed coat must meet certain specifications: (i) an appropriate thickness because the rate of germination and compound release is dependent on it, (ii) biodegradable because the degradation rate is a crucial parameter for the release of certain compounds, and (iii) environmentally friendly and non-toxic to seeds [27]. Because of this, the selection of materials has resulted in the utilization of a wide variety of biopolymers, one of which is based on alginate.…”

“…Because of this, the selection of materials has resulted in the utilization of a wide variety of biopolymers, one of which is based on alginate. Brown algae are the source of the natural polysaccharide known as alginate and it is commonly used to prepare hydrogel formulations with slow or controllable release qualities [27]. The material is simple to create, biodegradable and harmless, and it possesses the capacity to react to the conditions in the surrounding environment (including pH).…”

“…Alginate has also been used in agriculture, most commonly as a component of slow-release coatings or as transport for fertilizer ingredients. Even though research on the use of this polysaccharide in seed applications is still in its early stages, it is known that seeds can be coated with growth regulators, bacteria (Pseudomonas aeruginosa), and mycoparasites (Trichoderma asperellum) in an alginate coating [27].…”