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Nitrogen contributions in a windmill grass (Chloris truncata?) wheat (Triticum aestivum L.) system in south-western Australia


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Syme, H, Acuna, TL, Abrecht, DL and Wade, LJ 2007 , 'Nitrogen contributions in a windmill grass (Chloris truncata?) wheat (Triticum aestivum L.) system in south-western Australia' , Australian Journal of Soil Research, vol. 45, no. 8 , 635�-642 , doi: 10.1071/SR07159.

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Chloris truncata, a perennial grass that is native to Australia, has potential as a short-lived summer pasture in
rotation with wheat and other winter crops in the low to medium rainfall zone of south-western Australia. In this paper we
examine the nitrogen contributions from a C. truncata–wheat system, with the expectation that C. truncata may take up
nitrate which would otherwise be lost to leaching, for later release to the following wheat crop. In glasshouse experiments,
residual soil nitrate in bare soil was available for uptake and growth of wheat, with a greater response when N was applied.
In contrast,wheat grown on C. truncata stubblewas mostly reliant on recently mineralised nitrogen, as the previous rotation
had depleted the soil of nitrate. Shoot stubble of C. truncata provided sufficient mineralised nitrogen such that the uptake
of nitrogen and biomass of wheat equalled those from bare soil. Wheat grown on root stubble of C. truncata had half the
biomass production of that grown on either bare soil or shoot stubble, with root+shoot stubble intermediate. In a field trial
undertaken at Bruce Rock in Western Australia, nitrogen release from C. truncata stubble at low to intermediate stubble
densities increased tiller production, nitrogen uptake, and growth of wheat, but not at the highest N rate in this season,
which received below-average rainfall in July. These results provide initial evidence concerning how a C. truncata–wheat
system could improve the N balance of the farming system, by potentially reducing the leaching loss of nitrate in autumn,
and then releasing mineralised N from stubble when needed by a following wheat crop. While these results require further
confirmation, especially in the field, they raise exciting prospects for an improved agronomic system, with potential benefits
to N balance, carrying capacity, yield stability, and groundwater discharge. The system requires further study to quantify
these processes, and explore their implications.

Item Type: Article
Authors/Creators:Syme, H and Acuna, TL and Abrecht, DL and Wade, LJ
Journal or Publication Title: Australian Journal of Soil Research
Publisher: CSIRO Publishing
ISSN: 0004-9573
DOI / ID Number: 10.1071/SR07159
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