Effect of ammonium sulphate and related salts on the phytotoxicity of dichlorprop and other herbicides used for broadleaved weed control in cereals

Abstract

Summary In glasshouse experiments, additions of 10–100 g 1−1 ammonium sulphate enhanced the phytotoxicity to broadleaved weeds and cereals of several water‐soluble herbicides applied post‐emergence in 75–300 1 ha−1 with hydraulic nozzles. Studies with dichlorprop potassium salt and chickweed Stellaria media (L.) Vill. examined interactions between ammonium sulphate and environmental, application and formulation factors. Simulated rainfall immediately after spraying greatly reduced dichlorprop activity, whether or not ammonium sulphate was present. However, when there was an interval of 2–24 h between spraying and rainfall, the additive increased phytotoxicity. Surfactants tended to reduce dichlorprop phytotoxicity to Stellaria media, both in the presence and absence of ammonium sulphate. Certain other inorganic salts including sodium sulphate also enhanced phytotoxicity. Applications by rotary atomizer in very low spray volume (15 1 ha−1, 250–280 μm drops) were less effective than conventional 150 1 ha−1 applications. When very low volume application was used, addition of ammonium sulphate or nitrate tended to reduce activity further. In the field, ammonium sulphate significantly increased the effects against weeds of a commercial dichlorprop potassium salt formulation applied conventionally in 200 1 ha−1 spray volume. Neutralized phosphoric acid had a similar effect but a mixture of this additive and ammonium sulphate reduced phytotoxicity. Both additives slightly increased dichlorprop injury to barley.

Environment and Spray Additive Effects on Picloram Absorption and Translocation in Leafy Spurge (Euphorbia esula)

“…Ammonium sulfate applied with glyphosate increased control of some but not all weed species (26). Turner and Loader (30,31) suggested that ammonium salts increase the rate of herbicide penetration through leaf surfaces. Ammonium sulfate may have increased 14 Cpicloram absorption in leafy spurge by affecting plant rather than spray droplet characteristics.…”

AMMONIUM SULPHATE ENHANCES CONTROL OF ANNUAL GRASS WEEDS IN CANOLA (Brassica campestris) WITH SETHOXYDIM

“…), 2,4-D (Sexsmith 1953), picloram (Turner and Loader 1972;Wilson and Nishimoto 1975), dichlorprop (Turner and Loader 1984) and glyphosate (Blair 1975;Suwunnamek and Parker 1975;Loader 1975, 1980;O'Sullivan et al 1981). Enhancement of a non-water-soluble herbicide with ammonium sulphate was first reported for sethoxydim (Chow and MacGregor 1983 For the other species, the leaf-stage at the time of treatment was 4, 3, 4 (canola); 3, 3, 4 (green foxtail) and 3, 4, 3 (wild oat) for 1984, 1985 and 1986, respectively.…”

Herbaceous weed control in conifer plantations with hexazinone and nitrogen formulations

“…Wills and McWhorter (1985) cite other such examples. Ammonium sulfate has also been used to increase the phytotoxicity of some herbicides used in forestry, including the potassium salt of picloram (4-amino-3,5,6-trichoro-2-pyridinecarboxylic acid) (Turner and Loader 1972) the isopropylamine salt of glyphosate (Turner and Loader 1975O'Sullivan and others 1980) and the potassium salt of dichlorprop [( f )-2-(2,4-dichlorophenoxy) propanoic acid] (Turner and Loader 1984). Szabo and Buchholtz (196 1) demonstrated that leaf penetration of the triethanolamine salt of 2,4-D [(2,4-dichlorophenoxy) acetic acid] increased with addition of ammonium nitrate and disodium phosphate.…”