Hydrochar from rice straw as a bio-based slow-release fertilizer: Tuning temperature and oxidation for agronomic performance

Hydrochar from agricultural residues is a promising bio-based fertilizer product. We optimized rice-straw hydrochar slow-release fertilizers (SRFs) by varying hydrothermal temperature (200–280 °C) and post-oxidation (0–8 h), then compared them with a pyrochar SRF and a conventional fertilizer. The optimized hydrochar (H-240 and its oxidized H-6h derivative) showed high nutrient loading at 30.74 wt% of N and rich oxygenated surface groups favorable for nutrient binding. In water, the conventional fertilizer released up to 95 % of N within 1 h, whereas hydrochar SRFs cut the initial burst to 35 % (H-240) and 22 % (H-6h) and sustained release over 5–7 days; in sandy soil, they delayed 80–85 % cumulative N release…

• CA
  Chinese Academy of Agricultural Sciences

  Award: 2023YFD2300400
• NK
  National Key Research and Development Program of China