Densified and water-repellent biodegradable starch/PBAT composite films-packaged fertilizers: Prediction model, controlled-release mechanism and rice application

Despite the non-biodegradable petrochemical polymers-coated controlled-release fertilizers have revolutionarily promoted the agricultural production, more researches should be devoted to developing the biodegradable starch films-packaged controlled-release fertilizers. To inform the development of the starch films-packaged controlledrelease fertilizers, the water-repellent ability and the controlled-release characteristic of the starch films need to be enhanced. Here, the densified starch/PBAT composite films-packaged controlled-release fertilizers (DSCFs) with the excellent water tolerance, the superior controlled-release performance and the low film materials content (1-2 %) were fabricated using the simple and solvent-free process. The significantly reduced water vapor transmissions (1-fold) and the enhanced nutrient release longevities (20-100 days) can be flexibly regulated by adjusting the PBAT contents and the film thicknesses. To fast predict the nutrient release longevity, the prediction model between the longer nutrient release longevity at 25 degrees C water and the accelerated longevity at 40 degrees C water was established by the response surface methodology. The controlled-release mechanism was clarified by the three-dimensional computerized tomography scanning technology: The smaller and lesser micropores and the densified cross-linked network of the starch/PBAT films with the increasing PBAT content can effectively resist the water into and the dissolved nutrient out of the DSCFs films, hence improving the controlled-release characteristic. Furthermore, the starch/PBAT films can be biodegraded in the soil environment to reduce the residual film contamination. The dramatically increased rice yield (71.75 %) showed the reliable practical application value of the DSCFs. The development of the biodegradable DSCFs was benefit to foster the end-user confidence in the low-film-content controlled-release fertilizers.