Closing the nitrogen supply and demand gap using legume residue combined with fertiliser nitrogen input

School of Agriculture, Food & Wine, The University of Adelaide - Proceedings of the 2016 International Nitrogen Initiative Conference

Type: Conference Paper
Knowledge level: Advanced

Farm Table says:

This study is focused on the semi-arid Mallee region of SE Australia where N fertiliser rates are typically low and opportunities for late season application can be limited by a lack of rainfall events. As a result it is difficult to develop suitable N management strategies, leading to uncertainty for farmers when deciding on fertiliser N applications

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.

Final comment

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

Australia - School of Agriculture, Food & Wine, The University of Adelaide - Proceedings of the 2016 International Nitrogen Initiative Conference
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