A slow-release fertilizer formulation was prepared by incorporation of urea in polyvinyl alcohol–alginate hydrogel core followed by deposition of calcium carbonate coating using HCO3−/CO32−-rich alkaline cell-free ureolytic culture broth. High urea encapsulation efficiencies were evident in both CaCO3-reinforced (23.48% w/w) and regular (38.71% w/w) hydrogel matrices. Deposition of carbonate over the matrix surface in the reinforced hydrogel was evident from scanning electron microscopy and typical FTIR band near 1465 cm−1 due to C–O stretch of carbonate ion. Aqueous phase release behaviour was not significantly different between the two hydrogel variants. In the soil column, two-stage urea release pattern (i.e. a slow followed by a fast) was eminent that can extend into hours. Therefore, the modified hydrogel for controlled release could be expected to have wide potential application as slow-release fertilizer in agriculture.

中文翻译：

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作为控释尿素制剂的生物源性 CaCO3 增强的聚乙烯醇 - 藻酸盐水凝胶的制备和表征

通过在聚乙烯醇-藻酸盐水凝胶核心中加入尿素，然后使用富含 HCO3-/CO32- 的碱性无细胞尿素分解培养液沉积碳酸钙涂层来制备缓释肥料配方。在 CaCO3 增强 (23.48% w/w) 和常规 (38.71% w/w) 水凝胶基质中，尿素包封效率很高。由于碳酸根离子的 C-O 拉伸，从扫描电子显微镜和 1465 cm-1 附近的典型 FTIR 谱带可以看出，碳酸盐沉积在增强水凝胶的基质表面上。两种水凝胶变体之间的水相释放行为没有显着差异。在土壤柱中，两阶段尿素释放模式（即先慢后快）很突出，可以持续数小时。所以，