Arable growers are investigating alternative sources of nitrogen to reduce their crop reliance on synthetic nitrogen.
Hefty increases in the price of synthetic nitrogen, coupled with the likely introduction of pricing for nitrogen fertiliser-related nitrous oxide emissions, has led farmer groups in Canterbury and Waikato to look at different ways to supply nitrogen to their crops.
The Alternative N groups were formed as part of the Foundation for Arable Research (FAR) Growers Leading Change (GLC) programme.
The Canterbury group focused on cereal crops while the Waikato group concentrated on maize.
In the 2022-23 season, the Canterbury group tested a seaweed-based product containing a range of amino acids, applied in combination with reduced applications of synthetic nitrogen, to gauge whether this would provide the same yield as a standard nitrogen application.
The product was tried in autumn-sown wheat in seven paddocks over six farms.
The on-farm experiments are known as try-outs, rather than trials, as they are not fully scientifically replicated, but still provide a useful indicator for growers.
Canterbury GLC Alternative N group facilitator Donna Lill said the results showed no significant differences in yield between the standard and biological treatment.
However, greenhouse gas emissions, a key driver for the project, were lower with the biological treatment because of the 30% reduction in urea.
Growers are now experimenting with nitrogen-fixing faba beans to see how much nitrogen these provide cereal crops.
Faba beans have been planted as either a cover crop that was terminated when the autumn cereal was sown, or together with the autumn cereal as intercropping.
They are also investigating the nitrogen use efficiency of three different types of urea application on a cereal crop – liquid to soil, granular and foliar.
GLC group member Brent Austin, who farms at Lismore, near Ashburton, is growing faba beans both as a short-term autumn cover crop and with wheat and barley, to gauge what nutrients these provide to the growing crop.
He has applied liquid nitrogen on all his crops for the past four years.
While he would have potentially tried these things anyway, he said the amount of soil testing undertaken with being part of a GLC group is a bonus.
The group also generates a lot more useful data than an individual farmer can do alone.
“It’s also going and seeing other farmers’ try-outs and what they are doing. Talking to other farmers involved with the group is also important.”
In Waikato, growers are testing alternative nitrogen products, chicken manure, dairy effluent, composted dairy effluent and winter legumes, in combination with synthetic nitrogen to determine their impacts on maize yield.
