Development of a new kind of biodegradable polymer nanocomposes for application as coating in the slow and controlled release of soluble fertilizers

Abstract

Despite the indispensable use of agricultural fertilizers to achieve current levels of productivity, chemical nutrients have their effectiveness limited by problems such as ammonia (NH3) volatilization, leaching and/or soil immobilization. One strategy to minimize these problems is to protect the fertilizer with nutrient release barrier materials. Thus, it is desirable that the formed polymer should have a homogeneous adhesive line on the granule surface and be able to control the diffusion of soluble nutrients through its structure, allowing the barrier to assume an active role and not just that of a physical obstacle, which release would occur by mechanical compromise (fracture) of the polymer. The permeation through a polymer can be significantly reduced by the presence of internal diffusional barriers such as finely dispersed nanoclays (in the nanocomposites form). This strategy, although investigated for packaging materials (mainly to reduce gas permeation) has been neglected for fertilizer coating films as well as it has great potential to provide low permeation materials for this application. Thus, this project intends to develop strategies for the dispersion of lamellar nanoclays (mainly montmorillonite) as modifiers of a castor oil-based polymer matrix to control the release of commercial fertilizers such as urea and monoammonium phosphate (MAP). In addition, the project will also propose a new class of vegetable polyol based resins to obtain coating materials capable of controlling the release in low amount of application while maintaining biodegradability to ensure proper environmental incorporation after use. The coated granules will be evaluated to determine the best coating parameters, coating stability, deposition interface and total release time in water immersion and soil incubation assays. This proposal is expected to provide knowledge for a new line of high performance fertilizer products, focusing on sustainable alternatives for the widespread use of protective coatings in fertilizers. (AU)