13 November 2001
Should I apply late autumn N?
In min-tilled second wheat, should I apply nitrogen fertiliser? If so, how much and when? The crop is now at the one-leaf stage.
No need. There will be enough N around for these small plants.
The only concession to autumn N is if you direct-drilled, when up to 30 kg/ha might be justified in a 2nd wheat situation.
Measuring both soil mineral nitrogen (SMN) and nitrate content of drainage water under min-tilled fields has shown that N can be in short supply compared to ploughed soils.
This is exacerbated in second cereal situations, especially if the straw has been chopped and incorporated and the previous crop yielded well.
This year the problem has been reduced especially in early and mid-season drilled crops because the warm weather has kept soil temperatures higher than normal. This has kept up mineralisation of soil organic matter, making N available to the crop.
Rainfall patterns around the UK have been unusually variable, with some areas experiencing moisture deficits while in other areas drains have been running since early September.Later crops have not fared so well in wetter areas because N has been leached.
Given the time of year and the very undeveloped root system of a cereal crop at the one-leaf stage, I would not advise autumn N even if your drains are flowing. Better to wait until late February/ March and re-appraise the crop. An SMN sample prior to this might prove helpful.