A technique for measuring soil crust strengths

The vertical pressure required to fracture a soil crust from below the surface was measured. Disks (buttons) of 1.2 centimeters (.5 inch) in diameter were attached to a fishline, which was then covered by a soil crust developed from a mixture of sand and cement. Increased crust strength was attained by adding increasing amounts of cement to the sand. Gradually increasing pressure was applied using a pulley system with water as a counterweight. A scale recorded the maximum pull on the fishline for the disk to break the crust. A strong correlation (r2 = 0.96) existed between increasing amounts of cement and measured crust strength. A strong correlation also was observed between measured crust strength and percent emergence of soybean seedings (r2 = 0.98). These relationships accurately depict the effects of crust strength on soybean seedling emergence. The technique developed could be suitable for studying natural soil crusts.