Table 1. Regression equation of soil organic carbon mineralization rate and cumulative mineralization under different compounding ratios.

Index	Treatment	Regression equation	r
Mineralization rate	CK	y1= − 12.10 ln(x) + 41.28	0.7933**
	C1	y1= − 14.56 ln(x) + 54.378	0.9298**
	C2	y1= − 10.06 ln(x) + 40.408	0.9595**
	C3	y1= − 14.40 ln(x) + 64.713	0.8679**
Cumulative mineralization	CK	y2=71.928 ln(x) + 30.107	0.9935**
	C1	y2=132.40 ln(x) + 9.2284	0.9752**
	C2	y2=121.50 ln(x) − 14.676	0.9757**
	C3	y2=234.98 ln(x) − 60.922	0.9795**

** means significant correlation at 0.01 level.

CK

the volume ratio of soft rock to sand is 0:1

C1

the volume ratio of soft rock to sand is 1:5

C2

the volume ratio of soft rock to sand is 1:2

C3

the volume ratio of soft rock to sand is 1:1

y₁

CO₂ production rate, mg kg⁻¹d⁻¹

y₂

CO₂ accumulative release amount, mg kg⁻¹

x

incubation day, d