Urea loaded nanoclay biopolymer composites: synthesis, characterization and evaluation for enhancing nitrogen use efficiency

Different nanoclay polymer/biopolymer composites (NCPC/NCBPCs) have been synthesized for use in agriculture as a soil additive, nutrient reservoir and water superabsorbent. However, the potential of NCPC and NCBPCs as a slow-release fertilizer is still in its early stage and need to be studied thoroughly. Thus, the present study was performed to synthesize and assess the efficacy of urea loaded NCPC and NCBPC, as a slow-release nitrogen (N) fertilizer using rice as a test crop grown in an Inceptisol. A series of NCPC and NCBPCs was synthesized using acrylic, acrylamide and bentonite with varying concentration of biopolymer (wheat flour and maida). The XRD, SEM and FTIR analysis of these products revealed that the biopolymers took part in the graft polymerization reaction involving acrylic acid and acrylamide and after polymerization, the bentonite layers were distributed evenly throughout the polymer network. The results of the N release study revealed that as the concentration of biopolymers in the NCBPCs increased, the slow-release properties of the polymers were adversely affected, and the degradation rate of the products increased. The NCBPCs prepared with maida release N more gradually than the wheat flour NCBPC does. For pot culture studies, NCBPCs prepared with 20% wheat flour/maida (NCBPC(W20) and NCBPC(M20)) along with NCPC and commercial urea were used. NCPC treatment had the highest N recovery efficiency (RE) (70.1%), followed by the NCBPC(M20) (58.5%), NCBPC(W20) (48.0%) and urea (31.9%). According to the findings, applying 75% RDF of N through NCBPC and NCPC products resulted in significantly higher crop yields, N recovery, agronomic use efficiency (AUE) as well as maintained higher N availability in soil than that of 100% RDF of N applied through urea.Graphical abstractSchematic view of synthesis and characterization of nanoclay biopolymer composites for nitrogen use efficiency