Comparing Roundup Ready and triazine tolerant canola in crop rotations accounting for variable conditions

®(RR) canola to a rotation including triazine tolerant (TT) canola. Within these rotations, use of glyphosate as a knockdown herbicide has been compared with use of Spray.Seed ® . Net returns were found to fall in the longer term in all rotations. Net returns were highest initially but fell more rapidly in the RR rotation where glyphosate was used as a knockdown herbicide. Where Spray.Seed ® was used as a knockdown herbicide in the RR rotation the initial net return was lower, but the rate of fall in net return was reduced.