EFFECT OF RETARDANTS AND NITROGEN FERTILIZATION ON WINTER WHEAT CANOPY STRUCTURE

This paper presents the results of a study on winter wheat canopy architecture under the conditions of application of several retardants and two levels of nitrogen fertilization on loess soils in the south-eastern region of Poland, in the period 2004-2007. The present study investigated the effect of retardants, adjuvant and nitrogen fertilization rates on canopy architecture traits, such as: number and weight of grains per ear in different canopy layers, percentage of stems of different lengths in the canopy, and percentage contribution of individual canopy height layers to grain yield formation in winter wheat. The number and weight of grains per ear were most differentiated by the retardants Cecefon 465 SL and Antywylegacz Plynny 675 SL. The higher rate of nitrogen (150kg ha(-1)) and the adjuvant Atpolan 80 EC also had a positive effect on grain number per ear and percentage contribution of the individual height layers of the winter wheat canopy in grain yield formation especially in the highest canopy level. The retardants Antywylegacz Plynny 675 SL and Cecefon 465 SL increased the percentage of stems belonging to the 70-80 cm and 80-90 cm layers in the canopy as well as the percentage contribution of the above-mentioned layers to grain yield formation. The growth regulator Moddus 250 EC beneficially affected the productivity of stems belonging to the highest canopy layers (80-90 cm and above 90 cm).