AMADS Increases the Efficacy of Glyphosate Formulations on Corn1

Greenhouse studies were conducted to determine the effect of 1-aminomethanamide dihydrogen tetraoxosulfate (AMADS) as a spray adjuvant on the efficacy of three different glyphosate formulations, the isopropylamine salt (glyphosate-IPA), potassium salt (glyphosate-K), and the acid of glyphosate dissolved in AMADS (glyphosate-A). All formulations were tested at multiple rates with and without AMADS (2% v/v) on greenhouse-grown corn, and growth inhibition was determined by measuring the elongation of the newest emerging leaf between 1 and 7 d after treatment. AMADS increased the efficacy of all three glyphosate formulations by threefold to fourfold. The IC50 values for glyphosate-IPA, glyphosate-K, and glyphosate-A without AMADS on corn were 77, 54, and 53 g ae/ha, respectively; and with AMADS the values were 20, 18, and 21 g/ha, respectively. AMADS was more effective than ammonium sulfate (2% w/v) in overcoming the antagonism of hard water (200 parts per million Ca12) on glyphosate-K efficacy on corn. The rainfastness of glyphosate-IPA, glyphosate-A, and glyphosate-K was improved with AMADS. Nomenclature: Glyphosate; corn, Zea mays L. ‘Triumph 1416’. Additional index words: Ammonium sulfate, rainfastness, surfactant. Abbreviations: AMS, ammonium sulfate; DAT, days after treatment; glyphosate-TMS, formulated trimethylsulfonium salt of glyphosate; HAT, hours after treatment; IC50, concentration that inhibits growth by 50%; NIS, nonionic surfactant.