Abstract
Carrier water quality may affect the activity of weak acid herbicides when concentrations of some cations are high. A dose-response 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).
Highlights
Water is the most frequently used carrier for herbicide applications
Approaches to minimize hard water antagonism have included decreasing the spray carrier volume (Wills et al, 1998) and using water-conditioning additives (Thelen et al, 1995a) which have proven effective at ameliorating cation-caused antagonism include ammonium sulfate (Soltani et al, 2011), ammonium nitrate, potassium phosphate (Wills et al, 1998), and citric acid (Thelen et al, 1995b)
As judged by the relative potency values given in Tab. 1, the values were considerably higher than 1, indicating the enhanced glyphosate activity with addition/application of water conditioning methods when distilled water was used as carrier
Summary
Water is the most frequently used carrier for herbicide applications. its physicochemical properties in spray mixture can affect the absorption and/or activity of herbicides (Hoffmann et al, 2008). Weak acid herbicides that have been antagonized by one or more of the above cations include sethoxydim (Matysiak & Nalewaja, 1999; Nalewaja et al, 1989), glyphosate (Nalewaja and Matysiak, 1991; Bernards et al, 2005; Bailey et al, 2002), 2,4-D (Roskamp et al, 2013), clethodim (Nandula et al, 2007), imazethapyr (Gronwald et al, 1993), tralkoxydim (DeVilliers et al, 2001), and glufosinate (Pline et al, 2000) This antagonism is due to the formation of herbicide salts with a low solubility, resulting in a reduction in retention on the leaves (Hoffmann et al, 2008) and/or a reduction in absorption into the plant (Nalewaja et al, 1996). Approaches to minimize hard water antagonism have included decreasing the spray carrier volume (Wills et al, 1998) and using water-conditioning additives (Thelen et al, 1995a) which have proven effective at ameliorating cation-caused antagonism include ammonium sulfate (Soltani et al, 2011), ammonium nitrate, potassium phosphate (Wills et al, 1998), and citric acid (Thelen et al, 1995b)
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