Cellulose-based slow-release nitrogen fertilizers: Synthesis, properties, and effects on pakchoi growth

The application of most slow-release fertilizers is limited by complex preparation processes and short slow-release periods. In this study, carbon spheres (CSs) were prepared by a hydrothermal method using cellulose as the raw material. Using CSs as the fertilizer carrier, three new carbon-based slow-release nitrogen fertilizers were prepared using direct mixing (SRF-M), water-soluble immersion adsorption (SRF-S), and co-pyrolysis (SRF-P) methods, respectively. Examination of the CSs revealed regular and ordered surface morphology, enrichment of functional groups on the surfaces, and good thermal stability. Elemental analysis showed that SRF-M was rich in nitrogen (total nitrogen content of 19.66 %). Soil-leaching tests showed that the total cumulative nitrogen release of SRF-M and SRF-S was 55.78 % and 62.98 %, respectively, which greatly slowed down the release of nitrogen. Pot experiment results revealed that SRF-M significantly promoted the growth of pakchoi and improved crop quality. Thus, SRF-M was more effective in practical applications than the other two slow-release fertilizers. Mechanistic studies showed that C-N, -COOR, pyridine-N and pyrrolic-N participated in nitrogen release. This study thus provides a simple, effective, and economical method for the preparation of slow-release fertilizers, providing new directions for further research and the develop of new slow-release fertilizers.

Automated summary

In this study, carbon spheres (CSs) were prepared as a fertilizer carrier using cellulose, followed by the preparation of three new carbon-based slow-release nitrogen fertilizers using different methods. The direct mixing method showed the most effective promotion of pakchoi growth and crop quality improvement. Mechanistic studies revealed the participation of C-N, -COOR, pyridine-N, and pyrrolic-N in nitrogen release. This study provides a simple, effective, and economical method for the preparation of slow-release fertilizers and suggests new directions for further research and development.