Co-application of microalgae and biochar increases yield and mitigates greenhouse gas emissions in saline-alkali soil

Abstract

Context

Despite the proven role of biochar or microalgae application alone in yield stability and climate resilience, their synergistic effects have not been well characterized, especially in fragile saline-alkali lands.

Objective

This study aims to investigate the individual and combined effects of biochar and microalgae application on sunflower yield, soil carbon (C), greenhouse gas (GHG) emissions, and carbon footprint (CF), providing novel insights into saline-alkali soil management.

Method

Three doses of microalgae fertilizer (0, 30, and 60 L ha⁻¹), combined with two rates of biochar (0 and 30 t ha⁻¹), were applied in field experiments over 3 years in Northwest China (Wuyuan, Inner Mongolia). The key parameters evaluated included the soil organic carbon (SOC) content, GHG emissions, and crop yield.

Results

Microalgal fertilizer application alone caused minimal changes in SOC storage, whereas biochar application had a predominant effect, indicating that biochar was a key contributor to SOC accumulation. Notably, the combined effects of biochar and microalgae on yield, SOC storage, and emission reduction were stronger than those of each factor separately, confirming the positive complementary effects of dual application. The combination of microalgae fertilizer and biochar resulted in maximum yield (3824 kg ha⁻¹) and SOC sequestration (26 Mg C ha⁻¹), which increased by 58 % and 24 %, respectively, compared to that of the control over the three years. Additionally, co-application reduced GHG emissions and the CF by 18 %-31 % and 101 %, respectively.

Conclusion

The combination of 30 t ha⁻¹ biochar and 60 L ha⁻¹ microalgae was identified as the optimal strategy for the study area. This optimized regime holds great potential for increasing crop yield, enhancing C sequestration, and mitigating GHG emissions, thereby promoting sustainable development in saline agriculture.