Table 2.

Recent innovations related to CRFs/materials. Encapsulating material: Em.

CRFs/Materials	Remarks	Ref.
Biochar-based slow-release fertilizer (BSRFs) Em: Biochar and bentonite AI: K3PO4)	Keeping in view the promising properties of biochar as a soil amendment and a potential carrier for the slow-release of fertilizers, a biochar-based slow-release fertilizer (BSRFs) was synthesized by co-pyrolysis of corn straw, nutrients (K3PO4), and bentonite under microwave irradiation. The results highlighted that the presence of clay mineral (bentonite) in the synthesis process is beneficial to improve the controlled-release activity of BSRFs. The as-prepared BSRFs are cost-effective, eco-safe, and have high utilization efficiency.	[55]
Dual-release engineered phosphate fertilizers Em: Graphene oxide AI: mono-ammonium phosphate	A unique strategy was adopted to prepared engineered phosphate fertilizer with dual-release characteristics, i.e., fast and slowly soluble phosphorous by compaction method. The composition was made by mono-ammonium phosphate (MAP) acting as a highly soluble phosphorus nutrient source and a commercially available slow-release phosphorous, such as struvite (Str) or P-loaded graphene oxide. Briefly, the results highlighted the better performance of the dual-release phosphorous fertilizers as compared to MAP and Str.	[56]
Zein-coated porous carboxymethyl starch (PCS) Em: Zein (A natural polymer) AI: P and Fe	Zein-coated porous carboxymethyl starch (PCS) absorbent was prepared to enhance the utilization efficiency of phosphorous and simultaneously supply available Fe. The main objective was to develop PCS-Fe-P/Zein fertilizer. The reason for the inclusion of Fe (a microelement for chlorophyll synthesis) in the fertilizer was to act as a bridge between PCS and phosphate ions. Briefly, the results highlighted that the cumulative release of phosphorus in water was 18% in 30 days of duration. Moreover, the fertilizing effect of PCS-Fe-P/Zein was tested on soybean in a pot experiment and the utilization efficiency and uptake of phosphorous was 68%. The overall results indicated that PCS-Fe-P/Zein fertilizer has potential and sustainable application in agriculture.	[57]
Poly(tannic acid)-coated urea fertilizer Em: Tannic Acid AI: Urea	A novel green coating material, “a poly (tannic acid) (PTA)-coated fertilizers with urea prills as the core”, was prepared through a novel, simple method, “spout fluidized bed”, by using a natural polyphenol tannic acid (TA). The experimental results both in water and soil presented that the release rate of nitrogen from the as-prepared material was much lower than that from raw urea. The method developed in this paper is eco-safe for the preparation of SRFs has high potential in sustainable agriculture.	[58]
Controlled-release potassium chloride(CRK) Em: KCl AI: potassium (CRK)	A controlled release potassium chloride (CRK) was mixed with traditional KCl fertilizers in a 1:1 ratio to improve the utilization efficiency of potassium and lower the manufacturing cost. Based on experimental findings, the as-prepared CRK mixed with KCl was recommended for the delayed release of potassium to enhance soil fertility, increase crop yield on a sustainable basis, and maximize farmer’s income.	[59]
Degradable polyester/urea inclusion complex Em: Polyester AI: Urea	A facile solvent-free approach has been adopted to develop a novel environmentally degradable polyester/urea inclusion complex by one-step blending as slow-release fertilizers. Briefly, the results revealed that the polyester/urea inclusion complex showed a good slow-release rate compared to raw urea.	[60]
Sulfur-containing urea SRFs Em: Poly (eugenol sulfone) AI: Sulfur (S)	A novel slow-release sulfur-containing urea fertilizer with good biodegradation performance was synthesized by coating with sustainable poly (eugenol sulfone) derived from renewable eugenol and SO2 via simple free radical polymerization under mild conditions. The obtained results based on a set of designed experiments proved that the sulfur-containing urea fertilizer showed outstanding slow-release characteristics, biodegradation features and provides a new route for S-cycling.	[61]
Composites of biopolymers and ZnO NPs Em: Biopolymers AI: Zinc (Zn)	To increase the utilization efficiency of Zn micronutrient for plant growth, a composite composed of biopolymers (microcrystalline cellulose, chitosan, and alginate) and ZnO NPs (4–65% Zn w/w) was synthesized. The potential controlled release kinetics of Zn from the as-prepared composites in comparison to conventionally used Zn salts was tested in four different types of agricultural soils. Briefly, the results indicated that ZnO-biopolymers maintained a better constant supply of CaCl2-extractable Zn compared to all other treatments. Overall, the ZnO-alginate beads synthesized through crosslinking with CaCl2 showed the slowest controlled release kinetics of Zn.	[62]
Biodegradable urea-formaldehyde/poly(butylene succinate) and its ternary nanocomposite	Urea-formaldehyde-based or polybutylene succinate-based composites and nanocomposite used as a slow-release fertilizer in agriculture provide good feasibility for a large-scale application.	[63]
Nano-Delivery systems with Nature-Derived Polymers	Provided detailed scientific literature information on the advances in the innovations of nano-delivery systems using nature-derived polymers for agri-food applications.	[64]