Comparison of Desiccant Timing and Harvest Method in Canola.

A study was conducted at three locations in ND and MT from 2005-07 to evaluate the use of desiccants as a canola harvest aid.  The objectives were to determine the effect of desiccants applied preharvest at three timings on canola yield, seed moisture, and seed quality.  Paraquat was applied at 546 g/ha with NIS at 0.25% v/v.  Diquat was applied at 420 g/ha with NIS at 0.25% v/v.  One treatment was swathed with a plot swather as a comparison to current grower practices.  The paraquat, diquat, and swath treatments were harvested 7 and 14 days after treatment (DAT).  The study was a 3-factor factorial (desiccant, timing, harvest date) in a randomized complete block design.  Based on the results of this three-year study, there may be potential to successfully use a desiccant such as paraquat or diquat to desiccate canola without suffering unacceptable losses due to shattering or lower seed quality.  In these studies, if the desiccant or swathing operations were done when seed in the middle pods had started to turn color, crop quality parameters including canola yield, test weight, oil content, seed loss, green count, and grade were generally similar for desiccant treatments compared to swathing.  However, very early applications could result in lower yield and seed quality, most specifically higher green content.  Green count was generally lower when 1) plants were not lodged, 2) desiccants were applied when seeds in middle pods had started to turn, and 3) harvest moisture was near 10%.  Desiccated and swathed canola harvested 14 DAT had lower green count and less total damage than canola harvested 7 DAT.  Thus, leaving the crop in the field longer allowed seeds to continue maturing and drying.  There was minimal seed lost due to shattering at either harvest date.  Paraquat and diquat dried down the crop similarly.