The weeds correspond to areas of pooled water that froze to around six centimetres thick for three months and killed the crop. The weeds have filled the gap left by the crop.
The odd thing is in an adjacent field drilled at the same time, same seed rate, same variety, same everything there was very little or no winter kill. Also on slopes the level of losses is notably less.
What can you deduct from this? That oilseed rape will survive very low winter temperatures and is a viable crop in Ukraine even in a very cold year but can not tolerate being locked in to ice for extended periods of time? Possibly.
Would sub-soiling have helped? It might have allowed some of the melt water to drain away slightly quicker and reduced the depth of pooled water that re-froze to cause the higher than average levels of winter losses we saw this season.
Does that mean that sub-soiling will reduce the level of winter kill?
Possibly.
Sometimes the answer we seek is not in an obvious place.