Investigation on Characteristics of Natural Starch Based Coating as Potential Urea-Fertilizer Coating

The conventional fertilizer application oftentimes inefficient due to rapid release and leaching, which in turn caused pollution to the environment. The technique to control or slowing down the release of nutrients of the fertilizer in a controlled manner known as slow-release fertilizer (SRF). In sustainable agriculture, the utilization of natural starch as coating materials give alternative of the use of non-green materials. The abundance of natural starches may be serve as potential sources for sustainable fertilizer coatings. This study aims to investigate the properties of the urea fertilizer coated with several natural starch materials and to identify the most potent natural starch coating agents. The research was conducted as follows: 1) formulation of fertilizer coatings sourced from 7 natural starches (porang, gadong, sago, taro, sorghum, glutinous rice, and mung bean starches) and one synthetic materials (carboxymethoxyl cellulose, CMC); 2) granulation of urea fertilizer with coatings produced from the formulation, 3) manufacture of fertilizer coating from 7 natural starches. The SRF fertilizers were then tested for drip resistance and nutrient release. Formulation of fertilizer coatings was 2% w/v of natural starch with polyethylene glycol (PEG) and gum arabic. Granulation with coatings resulted in 73% of the granule produced met the desired size criteria (2.5-5 mm in size). Drip resistance test showed that CMC showed the highest durability, followed by gayong starch and sorghum starch, consecutively. Comparison of nitrogen nutrient release of urea-SRF on distilled water and 2% citric acid showed higher urea-SRF solubility in 2% citric acid. Natural starches—particularly gadong, glutinous rice, sorghum, sago, and porang—have shown potential as natural coating materials. However, since the observed parameters were limited to water hatches and nitrogen release, further research is needed to optimize the use of these starches as slow-release fertilizer (SRF) coatings across a broader range of parameters.