Results summary: Applying the whole season's N in one split with Didin gave a big boost to crop size and greenness in April, visible both in the field and from satellite NDVI. However, the 'farm standard' approach of three N splits caught up by July, such that treatment differences were no longer visible in the field or in satellite imagery. Averaged across the two trials, we estimate a yield penalty of 0.13 t/ha ± 0.25 t/ha (95% confidence interval) from applying N as a single split with Didin. With current high wheat prices, the cost saving from missing two fertiliser applications is not great enough to justify this yield loss.
Other trials have shown significant yield benefits from urease inhibitors applied with UAN, relative to the same N rates and timings without inhibitors; the average benefit is about 0.2 t/ha. But these two trials suggest that inhibitors may not sufficiently slow N availability and prevent N losses to allow application of the crop’s whole N requirement as a single split.
