New generation of controlled release phosphorus fertilizers based on biological macromolecules: Effect of formulation properties on phosphorus release

The main objective of this work was to study the possibility of using polysaccharides and lignin as a coating material for water-soluble triple superphosphate (TSP) granular fertilizers. In this study, composites based on three polysaccharides (sodium alginate (alginic acid sodium salt): AL, kappa-carrageenan: CR and carboxymethyl cellulose sodium salt: CM) and lignin (LG) were prepared. The lignin used was extracted from olive pomace (OP) biomass using the alkali method. The morphological, mechanical, and surface properties as well as the thermal behavior of the coatings were characterized and compared. Their morphology and thickness revealed by scanning electron microscopy (SEM) showed good adhesion between the fertilizer and coating materials. The results showed that the lignin-carrageenan formulation (LGCR) exhibited the highest water absorbency and elastic modulus. Release tests showed the effect of the TSP/biopolymer mass ratio and that the slowest P release was obtained with the LGCR@TSP formulation composite within 3 day. In addition, 59.5% and 72.5% of P was released after 3 days with the TSP/biopolymer mass ratios of 5/1 and 15/1, respectively, compared to 100% P release with the uncoated TSP