A potential Mg-enriched biochar fertilizer: Excellent slow-release performance and release mechanism of nutrients

A potential Mg-enriched biochar fertilizer (MBF) was successfully synthesized via pyrolysis of MgCl2-enriched corn straw and high-efficiency reclaiming of N- and P-containing nutrients from biogas effluent. Mathematical modeling and column leaching method demonstrated that the MBF exhibited excellent slow-release performances of total P and N with sustainable release rates. Leaching experiment indicated that the final accumulative release ratios of N and P from MBF were 7 times and 6 times lower than those of chemical fertilizer (CF), respectively. The mechanism study reveals that the P-release performance of MBF was not only controlled by the low solubility of Mg-P precipitates formed on the biochar surface, but also enhanced by the 'P-trap' effect of MgO through re-precipitation process of PO43-. Meanwhile, the N-release behavior of MBF was dominated by the multi-effects of biochar carrier, including the confinement effect and electrostatic attraction for NH4+, as well as the hydrogen bonds and pore-filling effect for N-containing organic matter. In addition, MBF significantly promoted the corn growth and enhanced the nutrient uptake efficiency of corn. These results suggested that MBF may therefore have promising potential in sustainable agriculture application with multiple environmental benefits. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The Mg-enriched biochar fertilizer (MBF) demonstrated excellent slow-release performances of total P and N, with mechanisms involving Mg-P precipitates and 'P-trap' effect of MgO for P-release, as well as confinement effect and electrostatic attraction for N-release. MBF significantly promoted corn growth and enhanced nutrient uptake efficiency, suggesting promising potential for sustainable agriculture with multiple environmental benefits.