Objective Glomalin-related soil protein (GRSP) is widely distributed in nature, and its hydrophobicity and stability of GRSP contribute to soil aggregation and soil carbon sequestration. Therefore, accurately determining GRSP content is crucial to explore the mechanism of GRSP on soil health.

Method Soils collected from alpine meadows on the Qinghai-Tibet Plateau, coastal forests, farmlands, urban green lands, and sediments in the East China Sea were divided into aggregates with particle sizes of < 0.053 mm, 0.053 ~0.25 mm, 0.25 mm ~ 2 mm, and > 2 mm. Easily extracted GRSP (EE-GRSP) content was determined under the different centrifugation times and delayed centrifugation times.

Result The content of EE-GRSP was the highest in the alpine meadow soil with a value of 0.79 ~ 1.09 mg g⁻¹, but less in the marine sediments of only 0.33 ~ 0.49 mg g⁻¹. Except for meadow soils and sediments, EE-GRSP content in the aggregates with a particle size of 0.053 ~ 0.25 mm was higher. In addition, the response of EE-GRSP content in different aggregates to centrifugation time and centrifugation delay time was different. The measured EE-GRSP contents in > 2 mm aggregates were not sensitive to the change in centrifugation time, while the values of EE-GRSP content in 0.025 ~ 2 mm aggregates were most affected by centrifugation time. Moreover, the centrifugal delay time did not significantly affect EE-GRSP content in forests and meadows as natural ecosystems containing higher EE-GRSP. However, the centrifugal delay time substantially influenced the EE-GRSP content determination in Marine sediments more than farmland and green land in artificial ecosystems.

Conclusion These results indicate that determining EE-GRSP content in soils of different ecosystems and soil aggregates with different particle sizes might be a significant overestimation or underestimation due to different centrifugation times or delayed time centrifugation. Therefore, it is recommended that the appropriate centrifugation time should be selected according to the soil samples and the centrifugal delay time should also be strictly controlled.