EFFECT OF AMMONIUM-SULFATE ON THE PHYTOTOXICITY, FOLIAR UPTAKE, AND TRANSLOCATION OF IMAZAMETHABENZ IN WILD OAT

Experiments were conducted in greenhouse, growth chamber, and laborato ry conditions to determine the effect of ammonium sulfate [(NH4)(2)SO4 ] on the phytotoxicity, foliar uptake, and translocation of imazametha benz on wild oat. Rates of (NH4)(2)SO4 up to 5% (w/v) applied with a g reenhouse sprayer did not affect the phytotoxicity of the herbicide wh en the mix was applied at the one- to two-leaf stage. However, inclusi on of 1 and 2% (NH4)(2)SO4 increased the phytotoxicity of the herbicid e when the mix was sprayed at the two- to three-leaf, or the three- to four-leaf stage. At 10%, (NH4)(2)SO4 decreased the phytotoxicity of t he sublethal dosage of the herbicide. When the herbicide was applied a s individual drops to the growth chamber-grown plants, inclusion of (N H4)(2)SO4 at 1% did not affect phytotoxicity as measured by shoot grow th. The presence of (NH4)(2)SO4 did not affect the amount of imazameth abenz retained by wild oat foliage, but it decreased [C-14]imazamethab enz absorption, slightly antagonized acropetal translocation, and incr eased the basipetal translocation of [C-14]imazamethabenz. It was conc luded that application methods greatly modify the effect of (NH4)(2)SO 4 on imazamethabenz phytotoxicity. Herbicide absorption and translocat ion as determined by one method do not necessarily represent the absor ption and translocation patterns when different application methods ar e used. Absorption and translocation were not the factors that were re sponsible for the observed effect of (NH4)(2)SO4 on the herbicide phyt otoxicity.