The efficacy of different application methods using reduced rates of herbicides and the possibility of decreasing total herbicide input were determined. Trials were carried out from 1994 to 1996 at Skierniewice, Poland. The weed control programmes were based on reduced rates of pre-emergence herbicides, followed by low rates of linuron applied early post-emergence as a single or split application. The complete rates of linuron and flurochloridone applied pre-emergence were 0.75 and 0.6 kg/ha, whereas the reduced rates were 0.375 and 0.3-0.4 kg/ha, respectively. Early post-emergence sprayings used linuron alone, either in single applications at the 1- to 2-leaf stage of carrots (0.25 or 0.375 kg/ha) or split applications at the cotyledon stage and 10-14 days later (0.19 + 0.19 or 0.19 + 0.5 kg/ha). The effect of pre-emergence diquat (0.6 kg/ha), followed by an early post-emergence split application of linuron (0.25 + 0.25 or 0.25 + 0.5 kg/ha) was also investigated. The effect of reduced dose rates of herbicides was compared to that of standard pre-emergence doses. The lowest herbicide rates gave acceptable weed mortality, but higher rates were more effective and often resulted in complete control. Pre-emergence rates of linuron and flurochloridone can be diminished by up to 50%. The weed control programme based on pre-emergence application of flurochloridone at low rates, followed by an early post-emergence split application of linuron was the most effective. No phytotoxicity symptoms were observed on carrots, even after post-emergence applications at early growth stages. The yields from herbicide treated plots were significantly higher than that from untreated plots. The differences between yields from plots treated with high and low herbicide rates were not significant.