Nitrogen fertiliser uptake by ‘grown on’ cotton in CQ
15 atom nitrogen (15N) is exceedingly rare in the natural environment and urea laced with this isotope can be used as a ‘label’ to track the fate of applied fertiliser. Two experiments in grown on cotton used 15N to understand plant uptake and potentially track remnant nitrogen over future seasons.
The two key treatments of interest were:
1. Base-applied 15N-enriched urea (250 kg N/ha) at planting followed by regular urea applied in-crop at cut-out (95 kg N/ha).
2. Base-applied regular urea (250 kg N/ha) at planting followed by 15N-enriched urea applied in-crop at cut-out (95 kg N/ha).
This experiment was done during the 2024/25 season at two irrigated cotton sites (Jabiwarra, Cowal Ag and Argoon, Morawitz Family) that had been planted late August/early September, grown on and picked in May. Partitioned biomass assessments were taken at cut-out and at final maturity.
Download the full experiment update & take-home messages from the experiments here. Uploaded April 2026.