The effect of adjuvants and reduced rates of crop protection agents on the occurrence of agricultural pests and on winter wheat productivity

A field experiment in growing winter wheat was carried out in Czesławice (the central part of the Lublin region) in 2009–2011. The experiment was set up as a split-block design with 3 replications on grey-brown podzolic soil derived from loess. Tillage was performed in accordance with the agronomic practices typical of this species. NPK mineral fertilization was adjusted to high soil nutrient availability. The research included 3 rates of herbicides, fungicides and a retardant (100, 75, 50%) as well as various types of adjuvants (surface-active, oil, mineral). Plots without adjuvant application were the control treatment. It was shown that a 50% reduction in the rates of crop protection agents caused a considerable decrease in winter wheat grain yield and in some yield components compared with the 75% rate and the maximum rate. Due to the addition of adjuvants (especially the oil adjuvant) to the spray solution, the reduction in the rates of crop protection agents by 25% did not cause any decrease of winter wheat productivity. A further reduction (by 50%) in the rates of crop protection agents, in spite of the application of adjuvants, had a negative effect on wheat yield caused by an intense accumulation of air-dry weight of weeds in the crop as well as by higher susceptibility of wheat to a complex of fungal diseases infecting the stem base