Crop responses to applications of both chlorsulfuron and monoammonium phosphate

Abstract

Field studies were conducted at two locations of different soil pH in Saskatchewan using preemergence chlorsulfuron and granular monoammonium phosphate. In year one, barley was not adversely affected by chlorsulfuron applied in the spring at 11.25 and 22.5 g a.i. ha−1 (Kernen location, soil pH 7.5) or 22.5 and 45.0 g a.i. ha−1 (Scott location, soil pH 5.5). In year two, the residual chlorsulfuron did not affect flax seed yield on the acid soil, but caused substantial crop damage to flax and lentil on the neutral soil. In general, flax and lentil were more injured by chlorsulfuron residues where lower rates of MAP had been applied the previous year, suggesting that the presence of a MAP band in the soil at the time of herbicide application may have slowed the rate of chlorsulfuron degradation. A corn-root bioassay procedure was adapted to estimate residue levels in soil samples taken from the field trials.