The response of soil organic carbon sequestration to organic materials addition in saline-alkali soil: from the perspective of soil aggregate structure and organic carbon component

Background and aims

Promoting soil organic carbon (SOC) sequestration is the key to improving soil quality. Adding organic materials is a common practice to promote SOC sequestration. However, the mechanism of SOC sequestration in saline-alkali soil with different organic materials addition is still unclear.

Methods

Field experiment was conducted: (1) Control, no fertilization; (2) NPK, only mineral fertilizer addition; (3) OF, NPK plus 2000 kg C ha^-1 addition of organic fertilizer; (4) MS, NPK plus 2000 kg C ha^-1 addition of maize straw.

Results

Compared with NPK treatment, the mean weight diameter (MWD) in OF and MS treatments was increased by 23.08% and 11.54%, respectively, which was due to the reduction of exchangeable sodium saturation percentage. Exchangeable calcium and magnesium were positively correlated with MWD, and their contents in OF treatment were 6.89-32.05% higher than those in MS treatment. Meanwhile, MWD was positively correlated with SOC stock, and small macro-aggregates contributed the most to SOC. Compared with NPK treatment, the ratio of mineral-associated organic carbon to particular organic carbon in MS and OF treatments were increased by 34.06% and 80.88%, respectively. Exchangeable magnesium and calcium could bind with polysaccharide, carboxyl and phenol to form complex under organic materials addition. Hence, SOC stock in OF and MS treatments was increased by 14.18% and 6.38% compared to NPK treatment, respectively.

Conclusion

The addition of organic materials improved the stability of aggregate structure and SOC pool in saline-alkali soil, thereby promoting SOC sequestration, in which organic fertilizer showed better effect.

Graphical Abstract