Laser Based Density Detection of Standing Wheat Stubble

Abstract

Penetration of a laser beam through wheat stubble was used as a measure of stubble density. A low power, heliumneon laser was positioned perpendicular to travel direction. A photo detector was used to determine penetration duty cycle after the beam passed through the stubble. Penetration duty cycle measured on a simulated wheat crop gave a good indication of crop density. The laser beam appeared to penetrate the simulated crop at densities where direct transmission was blocked. Some reflection of the laser beam occurred through simulated wheat stalks and off the filter on the sensor. Tests in standing wheat stubble offered little indication that the detector could accurately indicate crop density. Correlataon coefficients between stalk density and detector readings ranged between 0.60 and 0.07. A statistical model was developed to describe the system and eliminate the affect of hidden stalks. The model demonstrated the insensitivity experienced at higher stubble densities.