Weed infestation of a winter wheat canopy under the conditions of application of different herbicide doses and foliar fertilization

The present study was carried out in the years 2006-2008 in the Bezek Experimental Farm (University of Life Sciences in Lublin). A two-factor field experiment was set up according to a randomized block design, in three replications. The experimental field was situated on medium heavy mixed rendzina developed from chalk rock with medium dusty loam granulometric composition. The soil was characterised by neutral pH, a very high content of P (342.1) and K (278.9) along with a very low level of magnesium (16.0 mg × kg-1 of soil) and organic carbon (over 3.5%). The aim of this research was to compare the effect of three herbicide doses and two foliar fertilizers applied in a winter wheat canopy on weed infestation. The herbicides Mustang 306 SE 0.4 l × ha-1 and Attribut 70 WG 60 g × ha-1 were applied at full recommended doses as well as at doses reduced to 75% and 50%. Foliar fertilizers Insol 3 (1 1 × ha-1) and FoliCare (20 kg × ha-1) were applied at full recommended doses twice in the growing season BBCH* development stage 23-25* and 33-35*). The control was not treated with the herbicides and foliar fertilizers. The weed infestation level was determined by means of the quantitative gravimetric method at two dates: the first one 6 weeks after herbicide application and the second one - before harvest. The number of weed individuals was counted; species composition and air-dry biomass of aboveground parts were estimated from randomly selected areas of 1 m × 0.25 m at four sites on each plot. Galium aparine and Apera spica-venti plants were sampled for molecular analysis 6 weeks after herbicide application (the treatments with the full herbicide dose, a 50% dose and the control without herbicides). The density of weeds and weed air-dry weight were statistically analysed by means of variance analysis, and the mean values were estimated with Tukey's confidence intervals (p=0.05). It was found that the number of weeds and air-dry weight of weeds in the control treatment were significantly higher in comparison with the herbicide treated plots. The application of different herbicide doses did not differentiate significantly the weed infestation level in the winter wheat canopy. Galium aparine, Papaver rhoeas, Viola arvensis and Apera spica-venti were dominant weed species in the winter wheat canopy. Foliar application of fertilizers did not influence the weed infestation level in the crop canopy. Molecular analysis showed that herbicide application did not affect genetic variation in the populations of Galium aparine and Apera spica-venti.