Fertilizers play an essential role in agriculture due to the rising food demand. However, high input fertilizer concentration and the non-controlled leaching of nutrients cause an unwanted increase in reactive, unassimilated nitrogen and induce environmental pollution. This paper investigates the preparation and properties of slow-release fertilizer with fully biodegradable poly(3-hydroxybutyrate) coating that releases nitrogen gradually and is not a pollutant for soil. Nitrogen fertilizer (calcium ammonium nitrate) was pelletized with selected filler materials (poly(3-hydroxybutyrate), struvite, dried biomass). Pellets were coated with a solution of poly(3-hydroxybutyrate) in dioxolane that formed a high-quality and thin polymer coating. Coated pellets were tested in aqueous and soil environments. Some coated pellets showed excellent resistance even after 76 days in water, where only 20% of the ammonium nitrate was released. Pot experiments in Mitscherlich vegetation vessels monitored the effect of the application of coated fertilizers on the development and growth of maize and the dynamics of N release in the soil. We found that the use of our coated fertilizers in maize nutrition is a suitable way to supply nutrients to plants concerning their needs and that the poly(3-hydroxybutyrate) that was used for the coating does not adversely affect the growth of maize plants.

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The use of mineral nitrogen (N) fertilizers is associated with significant nitrogen loss through the volatilization. Ammonia (NH3) emissions are common from fertilizers with amide (NH2) and ammonium (NH4) nitrogen forms applied to the soil surface without incorporation. The objective of the laboratory and greenhouse pot experiments was to verify the hypothesis that liquid mineral fertilizers and fertilizer solutions containing N-NH2 and N-NH4 applied to the soil surface in combination with natural hydroabsorbents (NHAs) will reduce the volatilization of nitrogen. The effect of NHAs addition to urea ammonium nitrate (UAN) fertilizer and urea, ammonium nitrate (AN) and ammonium sulphate (AS) solutions was evaluated in a laboratory experiment. The effect of the two types of NHAs (acidic and neutral) was compared with the control (UAN) and its mixture with the commercially used urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT). The proportion of volatilized NH3 of the total N from the examined fertilizers applied to the soil surface was determined by the titration method. Subsequently, the effect of fertilization with UAN and its mixture with NHAs and NBPT on the growth of maize under the drought conditions was verified in a greenhouse pot experiment. While the addition of NBPT resulted in a reduction of NH3 emission for the fertilizers containing NH2 (UAN, urea solution), a decrease in volatilization after the addition of both acidic and neutral NHA was observed especially for UAN. A reduction in ammonia emission was also observed for AS after the addition of acidic NHA. The addition of both NHAs and NBPT to UAN increased the utilization of nitrogen from the applied fertilizer, which was reflected by an increase in chlorophyll content and increased CO2 assimilation by maize plants grown under the drought stress. UAN fertilizer combined with acidic NHA and NBPT significantly increased aboveground biomass production and root system capacity of maize. Significant increases in UAN nitrogen recovery were observed for all examined additives (UI and both types of NHAs). In addition to the known effects of hydroabsorbents, especially their influence on soil physical and biological properties and soil water retention, the effect of NHAs application in combination with UAN and AS solutions on the reduction of gaseous N loss, maize plant growth and fertilizer nitrogen recovery was found.