Using water hyacinth (Eichhornia crassipes) biomass and humic substances to produce urea-based multi-coated slow release fertilizer

Abstract

Urea-based multi-coated slow release fertilizer was produced using water hyacinth, humic substances, and chitosan, with water rich in natural organic matter as a solvent. Elemental analysis showed that the nitrogen content of the fertilizer (FERT) was around 20%. Swelling tests demonstrated the effectiveness of the water hyacinth crosslinker, which reduced the water permeability of the material. Leaching tests showed that FERT released a very low concentration of ammonium (0.82 mg L−1), compared to the amount released from urea (43.1 mg L−1). No nitrate leaching was observed for FERT, while urea leached 13.1 mg L−1 of nitrate. In water and soil, FERT showed maximum releases after 30 and 40 days, respectively, while urea reached maxima in just 2 and 5 days, respectively. The results demonstrated the promising ability of FERT to reduce nitrogen losses, as well as to minimize environmental impacts in the soil–plant-atmosphere system and to improve the efficiency of nitrogen fertilization. Graphic abstract

New Straw Coating Material for Improving the Slow-Release Performance of Fertilizers

“…Studies have shown that even when the amount of fertilizers used is reduced to 20–30% of the recommended value, the same crop yield can still be achieved with the application of coated fertilizers . Coated urea is prepared by coating the urea particles with the material having a lower water solubility, thus reducing the leaching of nutrient elements . The most commonly used coating materials are organic synthetic polymers, mainly including polyurethane, urea-formaldehyde resin, polyethylene, poly­(ether sulfone), and polystyrene. − The synthesis process of these organic polymers usually requires organic solvents such as dichloromethane and chloroform, , which can easily cause environmental hazards.…”

Urea–Straw–Starch Fertilizer with Tunable Water- and Nutrient-Retaining Properties Assisted by High-Energy Electron-Beam Irradiation

“…Water- and nutrient-retaining fertilizers (WNRFs) prepared by physical adsorption, , chemical crosslinking, − and coating , can release water and fertilizer into the soil continuously and slowly, which are particularly suitable for arid and semi-arid regions, − not only to promote crop growth and yield and reduce the frequency of fertilizer application but also to alleviate the environmental problems of eutrophication in water bodies caused by fertilizer loss. , Most types of WNRFs incorporate chemical polymers such as polyacrylamide and polyacrylic acid to adsorb water, − but this may cause potential environmental safety problems during fertilizer production and agricultural cultivation. , Therefore, the study of WNRFs based on nontoxic biobased materials will be beneficial to protect the environment and promote the sustainable development of green agriculture.…”