Applying nitrogen to rice in a wet year – it’s not straightforward!
Applying nitrogen to rice is normally straightforward, drill it into the soil prior to filling for aerially sown crops or broadcast it onto dry soil prior to applying permanent water in drill sown crops. This year however, the excessively wet conditions have caused complications which may require alternative approaches to be considered.
To maximise yield potential and economic returns while minimising risk it is important to measure nitrogen (N) uptake at panicle initiation (PI) so rice crop growth and N status can be assessed to allow accurate mid-season N topdressing decisions.
Back when grain yields of 10 t/ha were considered satisfactory, PI nitrogen topdressing was often enough to increase grain yields to 10 t/ha when insufficient nitrogen was supplied from the soil and pre-permanent water fertiliser.
Considerable scientific research over several decades has proven that applying nitrogen prior to permanent water for both aerial and drill sown rice is the most efficient practice, with panicle initiation applications running a close second. As we don’t have a rice soil nitrogen test and can’t predict seasonal temperatures, a split application between both timings is often the safest option, but what split is the best for yield and profitability?
We apply nitrogen fertiliser to rice at panicle initiation (PI) as a top up for any shortfall from soil nitrogen supply and pre-permanent water applied nitrogen fertiliser. Applying nitrogen at PI is relatively efficient and you can adjust the amount required depending on the crop’s growth, but how much can grain yield be increased by applying nitrogen at PI?