κ-Carrageenan–Sodium Alginate Beads and Superabsorbent Coated Nitrogen Fertilizer with Slow-Release, Water-Retention, and Anticompaction Properties

A multifunctional slow-release nitrogen fertilizer (SRNF) has been developed to improve fertilizer use efficiency and reduce environmental pollution. κ-Carrageenan–sodium alginate (κC–SA) and cross-linked κC-g-poly(acrylic acid)/Celite superabsorbent were used as inner and outer coating materials, which were coated consecutively on the granule core urea in a pan granulator. Elemental analysis result showed that the product contained 22.6% nitrogen. The water evaporation as well as the nitrogen release behavior of SRNF in soil was explored. In addition, the coated urea had a higher average crushing strength in comparison with uncoated urea. Furthermore, the incorporation of SRNF in soil could effectively prevent the compaction of soil. These studies showed that the product prepared by a simple route with good slow-release and water-retention properties may be expected to have wide potential applications in modern agriculture and horticulture.