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Controlled-Release Fertilizers: Innovations, Challenges, and Practical Applications
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This review paper looks at "slow-release" fertilizers designed to feed crops more efficiently while cutting down on runoff that pollutes water supplies. The catch: many of these fertilizers are coated in plastic to control how nutrients release, and that coating can break down into microplastics that end up in soil, water, and potentially our food. The researchers highlight promising plant-based and biodegradable alternatives being developed, but note more work is needed before these safer options are ready for widespread farm use.
Ensuring high crop productivity while reducing nutrient losses and environmental impacts remains a central challenge of modern fertilization strategies. Controlled-release fertilizers (CRFs) have emerged as a key tool to synchronize nutrient availability with plant demand by embedding soluble nutrient sources within coatings or matrices that modulate water penetration and ion diffusion. This narrative review synthesizes recent advances in CRF materials and technologies, with particular emphasis on biodegradable and bio-based systems, hydrogels, nanostructured carriers, and extrusion-based matrix formulations. It outlines the main classes of coating and matrix materials, their release mechanisms, agronomic performance, and documented benefits for nutrient-use efficiency, crop yield and quality, and soil and water protection. The review also analyzes major scientific, technical, environmental, and economic barriers that currently limit the large-scale deployment of CRFs, including microplastic pollution from persistent polymer coatings and the difficulty of tailoring release profiles under variable field conditions. Emerging directions are highlighted, such as composite and multilayer bio-based coatings, superhydrophobic and stimuli-responsive structures, biochar- and compost-based matrices, nutrient recovery from waste streams, and integration with precision agriculture and sensor technologies. The paper identifies priorities for future research needed to translate promising CRF concepts into robust, field-validated and sustainable fertilization solutions.
More Papers Like This
Techniques for encapsulating slow-release fertilizers using smart polymers: Towards controlled and sustainable release of plant nutrients: A review
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This review paper looks at "smart" fertilizer coatings that release plant nutrients slowly and only when crops need them, instead of dumping it all at once, a shift that could cut down on chemical runoff into rivers and groundwater. One catch worth noting: many of these coatings are made from plastic, which can break down into microplastics in soil, so the researchers highlight the need to switch to plant-based, biodegradable alternatives (like cellulose or chitosan) to keep this "smart farming" approach truly environmentally and food-chain safe.
Biodegradable Alternatives to Synthetic Polymer Coatings in the Production of Controlled-Release Fertilizers
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Many fertilizers used today are coated in plastic to slowly release nutrients into soil, but that plastic doesn't fully break down—it builds up in farmland as microplastics that can eventually make their way into our food and water. This review paper looks at plant-based alternatives (made from things like starches, plant fibers, and biodegradable plastics) that could do the same job of slow-release feeding without leaving lasting plastic residue behind. The research suggests these greener coatings show real promise, though scientists still need to test how well they hold up in real farm conditions before they can replace plastic coatings at a large scale.
Advancements and challenges in controlled-release fertilisers: An approach to integrate biopolymer-based strategies
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This review examines controlled-release fertilizers, which are designed to deliver nutrients to plants gradually, and finds that many use synthetic polymer coatings that can leave microplastic residues in soil. The authors highlight biopolymers made from natural materials like chitosan, cellulose, and starch as promising alternatives that can biodegrade without contributing to plastic pollution. The shift toward biodegradable fertilizer coatings could help reduce a significant but often overlooked source of agricultural microplastic contamination.
From Release Kinetics to Field Performance: A Critical Review of Slow- and Controlled-Release Fertilizers, Nutrient-Use Efficiency, Environmental Benefits, and Scale-Up Challenges
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This review of 130 studies finds that slow-release fertilizers work best when they match how fast crops actually need nutrients, not simply when they release nutrients slowly. It also flags a hidden downside: some coatings can leave behind microplastics or persist in soil, so environmental benefits must be weighed against these risks.
Mechanisms of microplastic generation from polymer-coated controlled-release fertilizers (PC-CRFs)
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This study investigated how the plastic coatings on slow-release fertilizers break down and release microplastics into soil. Significantly more microplastic particles were released in soil conditions than in water alone, and wet-dry cycles accelerated the breakdown, meaning agricultural soils receiving these fertilizers may be accumulating substantial amounts of microplastic pollution.
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