When to desiccate Oil Seed Rape
The desire to avoid interfering with the wheat harvest often tempts growers into desiccating their OSR too early.
It is not an easy decision and cannot be done by assessing crop colour changes from the gate. But it is financially important to get the timing of oilseed rape desiccation just right.
Desiccation too early risks both limiting oil percentage, (formed relatively late as the seed fills) and increasing the risk of immature red seed at harvest.
Spray timing needs to be based on assessments of pods from the area of the crop where the bulk of the yield is being carried, not necessarily the main raceme. The upper pods on the main raceme may be over-ripe, but any losses from here will be minor compared to the yield, oil and sample quality gains from the entire crop.
That means you have to get “in there” and collect a representative sample of pods on which to base a decision. When the colour in the majority of the seeds changes from green to brown the crop has reached the threshold of 30% seed moisture and desiccation maybe considered appropriate.
Of course there are other reasons to desiccate the crop such as the odd thistle!