While heavy, early rains can lead to significant losses of N applied at seeding, in-season foliar applications of Flexi-N can produce very good responses on waterlogged crops.
2021 was one of the wettest seasons on record at South Stirling, making it a good opportunity to analyse different nitrogen (N) strategies on a barley crop in a waterlogged paddock.
The year started with 103 mm of rain from January to March followed by 573 mm of rain during the ‘growing season’ - April to October. The crop established well but had to contend with waterlogged conditions right from sowing on May 6.
Nitrogen treatments included applications banded at seeding, early tillering (June 17), and at the start of stem elongation (July 13).
The site was very responsive to N. Applying increasing N rates post-seeding took yield from 4.7 t/ha (14N only at seeding) to 8.5 t/ha (217N spread across seeding, early tillering, and stem elongation) (Figure 1).
Figure 1. Yield increased with in-season Flexi-N (FN) applications.
Nitrogen use efficiency
With the early wet conditions, it was unsurprising that N applied at seeding was less effective than post-seeding applications.
In-season N applications had a nitrogen use efficiency (NUE) about double that of applications at seeding (Figure 2).
Figure 2. Crop recovery of nitrogen from Flexi-N (FN) applied at 120 and 240 L/ha banded (Bnd), early tillering (Z22), incorporated by seeding and banded (IBS + Bnd) or early tillering + early stem elongation (Z22 + Z30).
*assumes 75% of nitrogen taken up finishes up in the grain.
Figure 3. Trial site photo taken on August 4 highlighting the effectiveness of in season Flexi-N applications. Left 240L/ha Flexi-N banded; Right 120 L/ha applied at early tillering and start of stem elongation.