Farm Table says:
What is the problem?
In low-rainfall wheat cropping systems, low crop uptake of nitrogen (N) has been linked to asynchrony in
soil-N supply through mineralisation. This is especially true on sandy soils of SE Australia which have a
low-N supply capacity. When N released from soil and residues is insufficient, and/or the timing of
biological supply is not well matched with crop demand, manipulating N supply using fertiliser applications
becomes vital to achieve yield potential
Managing in-crop mineral-N availability using N fertilisation and legume crop residues has the potential to
close N-derived wheat yield gaps by improving N use efficiency, especially for south eastern (SE) Australian sandy soils with low N-supply capacity
What did the research involve?
The aim of this study was to measure the timing of N supply with crop N uptake for wheat following wheat-residues and wheat following lupin-residues under two N fertiliser rates in a low-rainfall sandy soil environment.
In each residue-type site, plants and deep soil samples to rooting depth were collected at sowing and at 5 key wheat growth stages.
Plants were analysed for N content, above-ground biomass and grain yield at maturity. All soil samples were analysed for gravimetric water content and mineral-N.
What are the key findings?
Responses in N uptake throughout the growing season indicate that there remains a demand for fertiliser N
following legume-N residue in this environment, but fertiliser N inputs remain risky as indicated by the lack
of significant yield increase in a low rainfall growing season.
In a dry season, the additional N supplied as fertiliser at early stages was a key input to support an increase in wheat yield potential