4182 11 archive 337 disk0/00/00/41/82 2008-04-07 14:26:22 2008-07-18 10:48:59 2008-07-16 17:05:35 article show Tina.Acuna@utas.edu.au Syme H Acuna TL Tina.Acuna@utas.edu.au Abrecht DL Wade LJ pub 070601 300302 820507 620101 restricted category => A1 categoryDesc => Refereed Article in a Scholarly Journal eprintID => 0 field1 => Australian Journal of Soil Research field10 => field11 => field12 => field13 => field2 => Australia field3 => 45 field4 => - field5 => 635–642 field6 => CSIRO Publishing field7 => 0004-9573 field8 => field9 => funding => A grant => lastUpdate => 7/01/2008 rfcd => 300302 seo => 620101 themeArea => SPP title => Nitrogen contributions in a windmill grass (Chloris truncata?)– wheat (Triticum aestivum L.) system in south-western Australia tor => PB uid => 49109 update => no 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. 2007 published Australian Journal of Soil Research 45 8 CSIRO Publishing 635–-642 10.1071/SR07159 TRUE 0004-9573 http://dx.doi.org/10.1071/SR07159 4819 3 4182 1 application/pdf en staffonly cc_utas

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