Cardinal temperatures for seed germination of wild barley, barley grass and hoary cress

It is necessary to understand the effects of environmental conditions, especially temperature, on weed seed germination patterns, in order to make comprehensive and effective weed management decisions. The effect of cardinal temperature (0 degrees C, 5 degrees C, 10 degrees C, 15 degrees C, 20 degrees C, 25 degrees C, 30 degrees C, 35 degrees C and 40 degrees C) on the germination pattern of three noxious weeds, such as wild barley (Hordeum spontaneum Koch.), barley grass (H. murinum L.) and hoary cress (Cardaria draba L.) in wheat fields of Iran, was studied in three separate experiments. The experiments were conducted based on completely randomized design (CRD) with four replications. The result showed that the germination of all three species started at low temperatures and there was no significant difference in germination percentage (GP) at lower temperatures. About 50% of the weed population germinated within a short period when using a dent-like model indicating the high ability of these weeds to compete for space and resources. Segmented and dent-like models were used to evaluate the cardinal temperatures. The results showed that dent-like model was the preferred model to evaluate germination rate in relation to variable temperatures in hoary cress, while the segmented model was better in wild barley. However, there was no significant difference between the two models for barley grass. The results of this study showed that mechanical, cultural (pre-planting irrigation) and chemical practices could be more useful and effective at 10-30 degrees C.