Delaying nitrogen applications by two to three weeks when oilseed rape crops are stressed could result in a yield penalty, according to The Arable Group.

Many forward crops had fertiliser applications delayed earlier this year, but the dry weather meant crops came under increasing moisture stress and were not able to take up nitrogen in the soil or fertiliser applied late, explained TAG’s Richard Overthrow.

“Any crop’s natural response to stress is to start flowering and set seed early, which is exactly what we’re seeing this year. Even crops that were treated normally are looking a bit thin, but it’s those which were thick coming into the spring and had nitrogen delayed that are really suffering.

“There are a lot of [winter] crops out there which have bolted – I’ve driven past quite a few that look more like spring rape.”

Mr Overthrow warned growers to be cautious when looking at trials that have found a positive yield response from later nitrogen timings on oilseed rape.

“On closer examination it appears that this is probably more a response to the total nitrogen applied, rather than timing. If the trial results suggest the yield response is down to the plant staying greener for longer, then it’s more likely the crop will need a desiccant in order to achieve a successful harvest.

“You’ll need to weigh up whether the extra input, pass and management costs are worthwhile.”