The concept of construction and testing the slot dispensing assembly for pneumatic and mechanical drills appeared during implementation of the development project No. N R003 0021 06/2009 at Poznań University of Technology. The paper contains the results of laboratory studies aimed at clarifying the impact of such factors as the type of grain, use of mixers, pressure in the seed tank to the seed rate of wheat and oats in the slot dispensing assembly. Laboratory tests were performed on the prototype of the pneumatic drill constructed at the Department of Working Machines with a built-in slot-dispensing assembly. For the same width of the slot opening, the dispensed amount of wheat seeds is dosed almost twice than the oats seed grain. The tests proved that the dosage in the unit dispensing slot would be impossible without the use of a mixer. Further research is planned for the slot dispensing assembly for other types of grains, small grains such as rape, in order to verify the usability and scaling the amount of sowing the seeds for a given slot opening.