Silicate–Phenolic Network (SPN) Coatings: Unlocking a New Era for Sustainable Controlled-Release Fertilisers
Written by Omid Mazaheri
Fertilisers and micronutrients are indispensable in modern agriculture, ensuring crops receive essential nutrients for growth and productivity. However, traditional fertilisers often suffer from inefficiencies, with nutrients being rapidly washed away due to rain or irrigation. This not only reduces their effectiveness but also contributes to environmental issues such as nutrient runoff and waterway pollution, which can lead to algal blooms in areas such as the great barrier reef. Additionally, the uneven release of nutrients can lead to over-fertilisation in some areas and nutrient deficiencies in others, ultimately harming crop yields and soil health.
Controlled-release fertilisers (CRFs) have emerged as a promising solution to address these challenges. By regulating the release of nutrients over time, CRFs minimise nutrient loss, improve crop uptake, and reduce environmental impact. Despite their potential, many existing CRFs rely on synthetic, non-biodegradable coatings that persist in the environment long after their use. These materials can contribute to microplastic pollution, undermining the sustainability goals they aim to achieve.
In our study led by Dr Omid Mazaheri at the University of Melbourne, we asked how to develop innovative coatings with biodegradable properties, which are likely to be non-harmful upon its usage as CRFs in the soil. Using compounds termed silicate–phenolic networks (SPNs), we developed robust, environmentally friendly coatings that provide superior nutrient delivery (Figure 1). The SPNs are engineered using natural polyphenolics and sodium silicate, creating coatings that are not only durable but also adaptable to various soil conditions and not environmentally harmful.
Figure 1. Shows the coating of an uncoated urea fertiliser granule (left – grey ball), with different types of SPN coatings. A granule can be modified to dissolve in soil and degrade faster or slower depending on the type of SPN coating and how dense the coating is.
The SPN coatings demonstrate several key advancements for controlled-release fertiliser (Figure 2). They responsive to soil acidity/alkalinity, ensuring fertilisers are released based on soil conditions, and how quickly they degrade when exposed to water can be customised, allowing precise control over release of fertiliser durations ranging from 7 to 14 days. Moreover, the coatings enable the release of silicon, and incorporated micronutrients such as iron, copper, and zinc over extended periods of up to 28 days. This dynamic and multipurpose delivery system reduces waste, improves nutrient efficiency, can be tailored to specific crops and supports sustainable farming practices.
To read in details about this topic:
Click here for the journal article by Omid Mazaheri et al.,
Learn more about Theme 1 research here.
