Efficacy and Selectivity of Pre-Emergence Herbicides in Production of Poplar Seedlings

Weeds represent one of the major problems in nursery production of seedlings, as they significantly affect the quality of planting stock, as well as the cost of production. Although there are several methods for weed control, the main task is to apply them as effective and economically viable control measures. The aim of our study was to investigate the efficacy and selectivity of herbicides in the nursery production of seedlings of two poplar clones (I-214 and Pannonia). The research results were based on three-year field experiments conducted at two sites that differed in soil physicochemical properties, weed flora composition, and seedling cultivation technology. Treatments included combinations of pre-emergence herbicides flurochloridone + dimethenamid-P, clomazone + S-metolachlor, dimethenamid-P + metribuzin, S-metolachlor + terbuthylazine, aclonifen + pendimethalin, flumioxazin + S-metolachlor, metobromuron + S-metolachlor, and mechanical measures. The results showed that all investigated herbicide combinations showed a high level of efficacy (>90%) in controlling weeds, unlike mechanical measures, which showed significantly lower efficacy (60–75%). All herbicide treatments significantly reduced weed biomass compared with mechanical measures, with an even more pronounced reduction compared with the control. Regarding phytotoxicity, all investigated herbicide combinations were selective except for the combination of aclonifen and pendimethalin, where aclonifen caused a phytotoxic effect on seedlings at both sites. Due to the phytotoxic effect of the combination of aclonifen and pendimethalin, seedlings exhibited lower diameter and height values. Also, high weed infestation on the control plots negatively influenced seedlings, resulting in significantly lower seedling diameters and heights.