Effect of pre-harvest application of herbicides on the seed production and properties of wheat and Glycyrrhiza glabra

Pre-harvest application of herbicides is considered as a way for decreasing seed production, vigour and germination of the weeds that have escaped from weed control methods and have the ability to increase the soil seed banks by producing their seeds. This study conducted to investigate the effects of pre-harvesting spraying on properties of wheat and Glycyrrhiza glabra seeds in different growth stages of wheat. This method also may cause damages to the crop seeds. A field experiment was carried out in split-split plot design with three replications. Experiment treatments consisted of different growth stages of wheat (milky, dough and seed ripening) as main plots, application of glyphosate (SL 41%) and paraquat (SL 20%) herbicides as sub-plots and different concentrations of herbicides (0, 1, 2 and 3 liters per hectare) as sub-sub plots. The results indicated that herbicides applied at different growth stages showed different effects on the properties of wheat and G. glabra seeds. Glyphosate and paraquat had different effects on the properties of wheat and G. glabra seeds. Given the various concentration levels of herbicides applied, different results related to different concentrations of herbicide were obtained. Application of 1 l/ha glyphosate at the seed ripening stage showed the lowest negative impact on the properties of wheat seeds and the highest negative effect on the properties of of G. glabra seeds.