R. Weber - Institute of Soil Science and Plant Cultivation, Department of Weed Science and Tillage Systems, Wrocław, Poland.
R. Kieloch - Institute of Soil Science and Plant Cultivation, Department of Weed Science and Tillage Systems, Wrocław, Poland.

Yield variability of selected winter wheat cultivars under different sowing rate and selected application, was investigated during 2006-2008, in the Lower Silesia region (South-West Poland). Experiments with two varieties, two levels of sowing rate and seven herbicides, including untreated object were set up on the same field, using split-plot method. For evaluation of yield stability Kang s yieldstability statistic (YS) was applied. Examined herbicides did not influence grain yield of both cultivars, at standard wheat density (450 seeds/m2). Under low density, Kobra Plus variety showed variable reaction to herbicides. Iodosulfuron methyl sodium + diflufenican + mezosulfuron methyl, mecoprop + MCPA + dicamba and iodosulfuron methyl sodium + amidosulfuron resulted in yield increment in comparison with untreated object, whilst dicamba + triasulfuron gave opposing effect. Yield stability at different herbicide objects during 3-years period was considerably variable and dependent on cultivar and sowing rate. Yield of both cultivars, obtained from plots treated with iodosulfuron methyl sodium + diflufenican + mezosulfuron methyl, iodosulfuron methyl sodium + amidosulfuron and mecoprop + MCPA + dicamba, under low density was comparable with standard sowing.

Wheat, Cultivar, Yield stability, Sowing rate, Herbicides