With increasing crop demand for nitrogen (N) fertiliser, what are the opportunities for increasing the efficiency of what we apply to cereals?
Are there efficiency gains from banding N at seeding compared to post seeding boom applications, and can banding N at the start of stem elongation give better results than streaming it onto the crop?
The advantages of banding N are mainly related to reduced potential for immobilisation losses, and to a lesser extent volatilisation – the risk of volatilisation being greater with urea.
On the other hand, N applied at seeding is more susceptible to leaching – in a leaching environment.
A trial on Scepter wheat at South Stirlings last year sought to compare the effectiveness of banding Flexi-N at seeding to streaming it on early post seeding, with another comparison of these methods at early stem elongation.
While the site was moderately (and profitably) responsive to N (with 151 kg N/ha lifting yields from 2.7 to 4.6 t/ha), there were no clear effects relating to either N placement of timing.
Compared to streaming Flexi-N, there was no agronomic benefit from banding N at seeding or at early stem elongation.
Most likely because there wasn’t enough stubble residue to tie up the N applied to the surface.
Compared to delaying the first application until the three leaf stage, banding Flexi-N at seeding was just as effective.
Conditions post seeding were relatively dry, so there was no risk of early leaching losses.
The benefits from banding Flexi-N are greatest where there are high stubble residues, and broadcast applications are uneven, or unavailable because they are not washed into the root zone.
Sure, banding N at seeding may be at susceptible to leaching, but that will only be in a leaching environment.
The risk of leaching losses needs to be weighed up against the risk of immobilisation losses and of course the logistics of any need to applying N over the season – particularly if high rates are required.