N higher after legumes than wheat

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A GRDC-funded project is examining the effect of legumes and canola break crops on subsequent cereal productivity in cereal-dominated cropping systems.

Higher grain protein was produced after lupins compared with after wheat or canola.

CSIRO researchers in partnership with grower groups and agribusiness consultants from New South Wales, Victoria and South Australia, and in collaboration with the NSW Department of Primary Industries and the Victorian Department of Environment, Land, Water and Planning, are investigating the effect of legumes and canola on available soil nitrogen (N).

One component of the research looked at the impact of soil inorganic (mineral) N from legumes on the subsequent wheat crop, as opposed to organic N in the soil, which is difficult to measure.

A trial near Junee, NSW, measured soil mineral N following lupins, wheat or canola and found that:

  • when lupins were sown for grain, there was 42 kilograms of N per hectare more soil mineral N available for the following wheat crop (compared with after wheat or canola); and
  • when lupins were sown for brown manure (BM), soil mineral N was 92kg N/ha greater than after wheat or canola.
When a second wheat crop was sown, concentrations of soil mineral N were:
  • 18kg N/ha higher for the lupins grain/wheat/wheat sequence (compared with after wheat or canola); and
  • 34kg N/ha higher for lupins BM/wheat/wheat.

What does this mean in terms of N utilisation? An additional 55 to 80kg N/ha was taken up by wheat grown after either a lupin crop (for grain or BM), compared with wheat following wheat or canola.

Higher grain protein (12.4 to 13.6 per cent) was produced after lupins, compared with about 9.9 per cent after wheat or canola.

More information:

Dr Mark Peoples, CSIRO,

mark.peoples@csiro.au

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Legumes a legacy with a modern role

GRDC Project Code CSP000146