G. Tihanov*

Department of Agricultural Engineering, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria

(Manuscript received 13 July 2020; accepted for publication 26 October 2020)

Abstract. A study on some operational characteristics of a direct sowing machine-tractor unit has been carried out in wheat sowing. It is performed by Horsch Avatar 6.16 SD direct seeder aggregated to John Deere 7250 R tractor. It was found that 91% of the area is sown at sowing rate of 195 kg seed/ha. The remaining 9% are sown either at lower or higher rate. Engine rotations of the seed unit have been established at work mode, i.e. when the seeder is sowing, these are 1594.81 min-1, in idle state the rotations are 912.08 min-1, and in transportation mode are 1860.36 min-1. The relative share of engine use has also been determined: when the seeder is sowing, it is 56.68%, when the seeder unit is in idle mode, it is 14.54% and when the unit is in transportation mode – 28.78%, respectively. The actual operation speed of the seeder unit when sowing wheat was 10.40 km/h and the real hourly productivity – 3.7 ha/h.