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Abstract:Composites consisting of polyvinyl alcohol, nitrogen-and phosphorus-containing waste materials were prepared and studied as materials for encapsulation of mineral fertilizers By-products of biodiesel production (rapeseed cake, crude glycerol), horn meal (waste product of haberdashery) and phosphogypsum (by-product of the production of phosphorus fertilizers) were used as the fillers of the composites. The films of the composites with the different amounts of nitrogen and phosphorus were prepared using different fillers or their mixtures. Mechanical, properties of the films, hygroscopicity, solubility in water were studied. The composites developed were used for the encapsulation of mineral fertilizers. It was established that encapsulation resulted in the increase of the time of release of the fertilizers. The developed slow-release fertilizers represent a combination of inorganic and organic compounds. The organic part consists of nitrogen-and phosphorus containing horn meal and rapeseed cake. Since assimilation of organic substances is considerably longer, nitrogen and phosphorus of these components will be available for plants much later than inorganic nitrogen and phosphorus. Thus the composite film will not only decrease the rate of desorption of the components from the granules of the fertilizers but will also prolong the impact of the fertilizers on the plants.

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The application of composites consisting of starch, rapeseed cake, crude glycerol, and urea for the fabrication of disposable biodegradable nursery pots is estimated. Mechanical properties of composite films, their hygroscopicity, solubility in water, and water vapour transmission rate were studied. The evaporation of water rate from the plant pots prepared from the composites was found to be twice lower than that observed for the commercial peat plant pots. The fluctuations of the soil temperature were also lower than in the commercial peat pots. The average time of the biodegradation of the composites was about one month. The rate of biodegradation depended on the species of microorganisms and on their physiological properties.