Abstract

Field experiments were conducted from 2008 to 2011, at western Hararghe zone, Eastern Ethiopia to evaluate the effect of urea and common salt treated glyphosate on parthenium weed (Parthenium hysterophorus). The experiments were arranged in randomized complete block design with five replications. Glyphosate herbicide at 3 L/ha was applied with different rates (0, 50, 100 and 150 ml) of urea and common salt. From the pooled analysis of variance over years it was observed that there existed a significant difference among treatments (p<0.05) in which the total population of parthenium weed mortality was noted at 25 days after applications across years for 3000 ml of glyphosate treated with 150 ml of urea and 150 ml of common salt. Results from this experiment showed that treating 3000 ml of glyphosate with 150 ml of urea and 150 ml of common salt solutions and spraying at 6 to 8 leaves stages resulted in complete mortality of parthenium weed in short period of time by increasing the phytotoxicity of this herbicide. While spraying this solution at 50 and 75% flowering stages showed poor mortality rates on this weed. This study also elucidated the complete change of parthenium infested plots into soft weed species that suppresses the re-emergency of this noxious weed. This helps in reducing the soil seed bank of parthenium weed, thus its population declines over successive years. This finding helps in reducing the rate and frequency of glyphosate application in conservation tillage and plantation crops like coffee and fruit farms, thus managing cost of parthenium weed can be significantly reduced.

Key words: Parthenium hysterophorus, glyphosate, mortality rate, phytotoxicity, soil seed bank.