Failed oilseed rape that received autumn nitrogen will not impact on Nitrate Vulnerable Zone (NVZ) limits for any replacement crop sown in the spring, advise agronomists.
The issue of crop failure has unfortunately been more common in some areas this season due to high levels of cabbage stem flea beetle damage, exacerbated by tricky weather during establishment, Lincolnshire-based Farmacy agronomist Charles Wright says.
As part of his planning for replacing the worst affected crops in the spring, he sought Environment Agency (EA) clarification about the impact that autumn-applied fertiliser might have on NVZ limits.
“If, for example, an autumn-sown oilseed rape crop received 30kg N/ha as a starter fertiliser, manure or autumn dressing, the EA confirms this does not have to be taken into account in the NVZ N-Max calculation for the new spring crop."
The two crops should be treated completely separately, although growers should retain full field records of the failed crop to document what was done, Farmacy's Charles Wright before starting a new record for the next one, he says.
It would therefore be permissible for growers to replace failed oilseed rape with another break crop such as spring peas or beans as the N-Max limit of 0kg/ha for these crops will not have been broken, Mr Wright says.
“When you have a bad year and crops fail, the key thing is to make sure it doesn't affect more than one season. In the case of oilseed rape, it is often grown as a break ahead of first wheat, so growers will be keen to maintain that break crop option with any replacement.