Simulating the partitioning of winter rape biomass by increasing the cutting height of stems

In three seasons 2010-2013, field experiments with two hybrid cultivars of winter oilseed rape were conducted in three localities in Southern Poland, with the aim of assessing changes in the harvest index, as compared to the agricultural harvest index of winter oilseed rape, defined as the harvest index decreased by the stubble height in relation to three plant categories (small, medium and large). As a result, an increase in the height of the stubble of winter oilseed rape in the range of 0-60 cm led to an increase in the agricultural harvest index value by about 0.081 for cv. ‘Adam’, and by 0.078 for cv. ‘Poznaniak’. The agricultural harvest index values were changed mostly by the vegetative seasons (p < 0.001). An increase in the height of the stubble of winter oilseed rape by 10 cm increased the agricultural harvest index of small, medium and large plants by about 0.091, 0.075 and 0.073, respectively, as compared to the harvest index values. The linear correlation between the height of the stubble of the winter oilseed rape plants and their agricultural harvest index was significant (R2 = 0.97-0.99). Depending on the factor (cultivar, locality, vegetative season or plant category), an increase in the height of the stubble of winter oilseed rape by 10 cm contributed to an improvement in agricultural harvest index from 0.012 to 0.015 g g-1.