Carrier water quality may affect the activity of weak acid herbicides when concentrations of some cations are high. A doseresponse experiment on glyphosate and imazethapyr activity, which were carried by the carrier types of distilled water and hard water, against jimsonweed were conducted to compare the water conditioning chemicals ammonium sulfate, ammonium nitrate, citric acid and potassium phosphate, with magnetized carrier as a new method. A magnetic field of 0.7 Tesla was applied to prepare the magnetized carrier. With the exception of potassium phosphate with imazethapyr, the activity of glyphosate and imazethapyr was significantly increased in the presence of the water conditioning methods when distilled water was used as the carrier. Ammonium sulfate was the most effective method. The activity of both herbicides was decreased when applied with hard water carrier. Potassium phosphate was not effective at reducing the antagonism of cations in the hard water carrier. In glyphosate, the performance of water conditioning methods in softening hard water carrier could be ranked as follows: ammonium sulfate (2.52-fold) > magnetized carrier (2.12-fold) < citric acid (1.64-fold) < ammonium nitrate (1.39-fold) > potassium phosphate (0.96-fold). In imazethapyr, this order was as follows: ammonium sulfate (2.99-fold) > ammonium nitrate (2.66-fold) > magnetized carrier (1.81-fold) < citric acid (1.64- fold) > potassium phosphate (1.10-fold).

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