Radiation synthesis of urea/hydrogel core shells coated with three different natural oils via a layer-by-layer approach: An investigation of their slow release and effects on plant growth-promoting rhizobacteria

Single and double-coated water-retention urea fertilizers were prepared by crosslinking urea with poly acrylonitrile (PAN) alone and with PAN-based poly acrylic acid (PAAc) hydrogels, respectively. In the first synthesis, the urea granules (the core) were coated with three different natural oils, namely epoxidized soybean oil (ESO), oleic acid (OA), and linseed oil (LO), to form the first shell. The second shell was formed with PAN and PAN-based PAAc hydrogels, as the two categories. The polymerization reaction was performed, employing various doses of gamma (gamma)-ray irradiation. Further, the effect of the various doses of gamma irradiation on the slow-release property of urea was examined in water. The results indicated that the two kinds of polymers had regulated the release of urea. Additionally, the water-retention properties of the coated urea were also studied. As observed, the slow-release property of urea PAN was better than that of urea-PAAc/PAN in all the three samples. The results further indicated that urea-PAAc/PAN exhibited good urea slow-release property and also possessed excellent water-holding capacity, which could exert better effects on fertilizer and water supplies. Additionally, the in vitro antibacterial activity of the urea granule coatings with hydrogel against plant growth-promoting rhizobacteria (PGPR) was investigated. The in vitro antibacterial potential demonstrated that there was no zone of inhibition (ZOI) around the tested samples of urea-PAN and urea-PAAc/PAN. This indicated that the synthesized urea granule coatings with hydrogel exhibited no antagonistic effect on PGPR and was, therefore, safer for utilization in agricultural fields.

Automated summary

In this study, single and double-coated water-retention urea fertilizers were prepared by crosslinking urea with PAN and PAN-based PAAc hydrogels. The polymers were found to regulate urea release and exhibit good water-retention properties. Additionally, the coatings with hydrogel showed no antagonistic effect on plant growth-promoting rhizobacteria, making them safe for agricultural use.