Physicochemical and microbiological properties of a vermicompost-based biocapsulated fertilizer and its association with early maize growth

Introduction Vermicompost-based encapsulated fertilizers may support organic-waste valorization and crop nutrient management under arid conditions. However, little is known about formulations combining vermicompost with biodegradable alginate–bentonite matrices. This study developed a vermicompost-based biocapsulated fertilizer, characterized its physicochemical and microbiological properties, and preliminarily evaluated its association with early maize growth. Methods Vermicompost was incorporated into a calcium-crosslinked sodium alginate–bentonite matrix to produce spherical biocapsules. The formulation was characterized by optical microscopy, Fourier-transform infrared spectroscopy, physicochemical analyses, and shotgun metagenomic sequencing. A randomized field experiment included an unfertilized control, conventional NPK fertilizer, and biocapsulated fertilizer, with three replicate plots per treatment. Maize height was measured 20 and 40 days after sowing, and differences were evaluated using one-way ANOVA followed by Tukey’s HSD test. Results The biocapsules exhibited predominantly spherical, compact morphology, an average diameter of 3.8 ± 0.4 mm, and a slightly alkaline pH of 8.3. FTIR features were consistent with organic, polymeric, and aluminosilicate components in the composite matrix. The vermicompost contained 35.2% organic matter, 24.15% humus, 1.68% nitrogen, 1.20% P 2 O 5 , and 1.90% K 2 O, with a taxonomically diverse microbial community. At 20 days, maize height was 14.2 ± 0.8 cm with biocapsulated fertilizer, 11.1 ± 0.7 cm with NPK, and 7.4 ± 0.6 cm in the control. At 40 days, values were 43.1 ± 1.8, 30.8 ± 0.7, and 19.2 ± 1.0 cm, respectively. Differences were significant at both times (p< 0.05). Discussion Under the tested conditions, the complete vermicompost–alginate–bentonite formulation was associated with greater early maize height than the control and NPK treatments. However, treatments were not nutrient-equivalent, and vermicompost-only, vermicompost–alginate, and alginate–bentonite carrier controls were absent. Thus, differences cannot be attributed specifically to encapsulation or interpreted as evidence of superior fertilizer-use efficiency. This preliminary study supports further investigation of the formulation for organic-waste valorization. Nutrient-release kinetics, soil nutrient availability, plant nutrient uptake, biomass, yield, and long-term soil effects require evaluation before controlled-release characteristics and agronomic effectiveness can be established.