WATER HARDNESS AND pH IN THE EFFECTIVENESS OF GLYPHOSATE FORMULATIONS

ABSTRACT The hardness and pH of the spray water can interfere with the weed control effectiveness with herbicides, but it is not clear the magnitude of this interference, mainly associating different levels of pH and hardness to different glyphosate formulations. This study aimed to evaluate the influence of hardness and pH, in association, of the water used in the application of two glyphosate formulations on the weed control effectiveness. The experiment was conducted in duplicate, in areas with a predominance of Digitaria horizontalis, under a randomized block design with a 4×4×2+1 factorial scheme, composed of four water hardness levels (70, 110, 230, and 430 ppm CaCO3), four pH levels (3.5, 4.5, 5.5, and 6.5), two glyphosate formulations (ammonium salt and potassium salt), and control without application, with four repetitions. The physicochemical characteristics of the spray solutions and the weed control effectiveness were evaluated at 7, 14, and 21 days after application (DAA). The water pH at the studied range did not interfere with the control effectiveness. The increase in hardness reduced the control at 7 DAA, but this difference was not noticed after 21 DAA. Glyphosate ammonium salt promoted higher control of D. horizontalis than that with potassium salt, regardless of water hardness and pH.

摘要：喷施用水的硬度与pH值会对除草剂的除草效果产生干扰，但目前尚不明确该干扰的作用幅度，尤其是在将不同水平的pH值与水硬度和不同草甘膦制剂相结合的场景下。本研究旨在评估两种草甘膦制剂施用时所用水的硬度与pH值的联合作用对除草效果的影响。本实验以横生马唐（Digitaria horizontalis）为优势杂草的地块为研究对象，采用随机区组设计，设置4×4×2+1因子方案，实验以双重复形式开展，每个处理组设置4次重复，包含4个水硬度水平（70、110、230、430 ppm CaCO₃）、4个pH水平（3.5、4.5、5.5、6.5）、2种草甘膦制剂（铵盐与钾盐），以及1个无喷施空白对照。分别于喷施后7、14、21天（DAA）对喷施液的理化特性与除草效果进行测定。结果表明，在所研究的pH范围内，水的pH值未对除草效果产生显著干扰。水硬度的提升会降低喷施后7天的除草效果，但该差异在喷施后21天不再显著。无论水的硬度与pH值如何，草甘膦铵盐对横生马唐的防控效果均优于钾盐制剂。