1. Department of Food and Agriculture Production Engineering , Collegium of Natural Sciences , University of Rzeszow , St. Zelwerowicza 4, 35-601 Rzeszów , Poland
2. Institute of Soil Science and Plant Cultivation, National Research Institute , Pulawy, Department of Weed Science and Tillage Systems , Orzechowa 61 St., 50-540 Wroclaw , Poland