Study on the use of polymer/bentonite composites for controlled release

Controlled release technology has emerged as a potential approach to settle the problems associated with the application of conventional fertilizers. Great advances have been made on the use of polymers as controlled release materials for slow-release fertilizers. Swelling polymer can absorb lot of water from aqueous solution and swell at the same time,therefore it has been applied in many fields, e.g. medical treatment, water treatment, agriculture and other relevant fields. Polyacrylamide hydrogels and its derivatives are used in agriculture as carriers of agrochemicals and soil (conditioners). Polymer/bentonite composites were used as controlled release materials in this study because of its lower production cost and better purpose for controlled release. Polymer/Bentonite composites were prepared with acrylamide and bentonite by polymerization. The mass of Bentonite in the composites 0B, 0.5B, 1B, 2B are 0, 0.5, 1, 2 times more than the polymer, respectively. Mixed controlled release fertilizers (MCRFs) were prepared by mixing polymer/bentonite composites with fertilizers. The MCRFs 0M, 1M, 2M, 3M, 4M were made of bentonite, 0B, 0.5B, 1B, 2B mixing with fertilizers, respectively. Coated controlled release fertilizers (CCRFs) were prepared by coating urea with polymer/bentonite composites. The CCRFs 0U, 1U, 2U, 3U, 4U were made of bentonite, 0B, 0.5B, 1B, 2B mixing with fertilizers (respectively). Both MCRFs and CCRFs were used for pot experiments. The results showed that both polymer and (bentonite) were of controlling release function, however, the function of controlling release of composites was better. In MCRFs (pot) experiments, (corn) biomass of MCRF treatments increased markedly compare with CK with the best amount being 2M MCRF. The recovery of N, P, K in MCRF treatments were higher than that in CK. In CCRFs pot experiments, corn biomass of CCRFs treatments increased markedly compare with CK with the best treatment being 4U. The different reached a significant level. The recovery of N in CCRFs treatments were higher than in CK.