The pH and hardness of water used as agrochemical carrier can influence herbicide efficacy. The objective of this research was to determine the role of carrier water pH and hardness on saflufenacil efficacy and solubility. Saflufenacil was mixed in eight different carrier waters with one of five pH levels (4.0, 5.2, 6.5, 7.7, 9.0) or one of three hardness levels (0, 310, 620 mg L−1) and applied POST to common lambsquarters and giant ragweed in a field experiment and to field corn in a greenhouse experiment. Solubility testing was also completed on saflufenacil mixed in the five pH levels used in the field and greenhouse experiments. Water hardness did not influence the efficacy of saflufenacil on common lambsquarters, giant ragweed, or field corn. Control of giant ragweed or common lambsquarters in field experiments was reduced by up to 56% when saflufenacil was applied in water with a pH of 4.0 compared with water with a pH of 7.7. When nonsoluble saflufenacil was removed from the spray solution, saflufenacil efficacy on field corn in the greenhouse was reduced by 61% or more when applied in water with a pH of 4.0 than when applied with water with a pH of 5.2 or higher. When nonsoluble saflufenacil was applied with the soluble saflufenacil in the spray solution, at least a 7% reduction in control of field corn was observed when applied in water with pH of 4.0 as compared with saflufenacil applied in water with pH of 5.2 or higher. Solubility of saflufenacil was (1) 10.1 mg L−1 in water with a pH of 4.0, (2) 3,461.4 mg L−1 in water with a pH of 7.7, and (3) > 5,000 mg L−1 at a pH of 9. Some degradation of parent saflufenacil was detected in the pH at 9.0 treatment, with only 90% of added product being recovered after 3 d of storage. This research provides information on how saflufenacil efficacy and solubility is influenced by carrier water pH and potentially explains some differences noticed between field applications of saflufenacil.
Nomenclature: Saflufenacil; common lambsquarters; Chenopodium album L. CHEAL; giant ragweed; Ambrosia trifida L. AMBTR; corn; Zea mays L.
El pH y la dureza del agua usada como medio para aplicaciones de agroquímicos puede influenciar la eficacia de los herbicidas. El objetivo de esta investigación fue determinar el rol del pH y dureza del agua para aplicación en la eficacia y solubilidad de saflufenacil. Se mezcló saflufenacil en ocho medios acuosos diferentes con uno de cinco niveles de pH (4.0, 5.2, 6.5, 7.7, 9.0) o uno de tres niveles de dureza (0, 310, 620 mg L−1) y se aplicó POST a Chenopodium album y Ambrosia trifida en un experimento de campo y a maíz en un experimento de invernadero. También se completaron pruebas de solubilidad a las mezclas de saflufenacil con los cinco niveles de pH usados en el experimento de campo y en el de invernadero. La dureza del agua no influenció la eficacia de saflufenacil sobre C. album, A. trifida, o maíz. En los experimentos de campo, el control de A. trifida o C. album se redujo hasta en 56% cuando saflufenacil se aplicó en agua con un pH 4.0 al compararse con agua con pH de 7.7. Cuando saflufenacil insoluble fue removido de la solución de aplicación, la eficacia de saflufenacil en maíz en el invernadero se redujo en 61% o más cuando el agua de aplicación tuvo pH de 4.0 en comparación con agua con pH de 5.2 o mayor. Cuando se aplicó saflufenacil insoluble con saflufenacil soluble en la solución de aplicación, se observó una reducción de al menos 7% de cont
