A Preliminary Study of Seeding Absence Detection Method for Drills on the Soil Surface of Cropland Based on Ultrasonic Wave without Soil Disturbance

Table 2

Soil properties.

Soil depth (cm)	Type	Bulk density (g.cm^−3)	SOM (g.kg^−1)	Soil moisture content (%)	Soil aggregate structure
					>2 mm	2~1 mm	1~0.25 mm	0~0.25 mm
0~20	Sandy loam	1.22	11.5	11.6	4.20	7.81	44.30	43.69