Abstract. Experimental research of rotary harrow Arterra Grip 400 was carried out to determine the value of vertical rotors’ kinematic parameter which provides the necessary soil’s crushing to pieces depending on the constructive parameters and the harrows duty. Two-factor experiment was implemented to determine soil’s crushing to pieces depending on the forward speed and harrow’s working depth. Vertical rotor’s critical kinematic parameter – =2,97, harrow’s marginal КР forward speed v=1,8 m/s and step S=15,8 cm were determined as a result of the research. During the research it was determined that 85% of soil fractions up to 50 mm can be achieved: at working depth 6 cm forward speed maximum of 2,3 m/s; working depth of 9 cm forward speed maximum of 1,8 m/s.