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1 September 2014 High Seed Retention at Maturity of Annual Weeds Infesting Crop Fields Highlights the Potential for Harvest Weed Seed Control
Michael J. Walsh, Stephen B. Powles
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Seed production of annual weeds persisting through cropping phases replenishes/establishes viable seed banks from which these weeds will continue to interfere with crop production. Harvest weed seed control (HWSC) systems are now viewed as an effective means of interrupting this process by targeting mature weed seed, preventing seed bank inputs. However, the efficacy of these systems is directly related to the proportion of total seed production that the targeted weed species retains (seed retention) at crop maturity. This study determined the seed retention of the four dominant annual weeds of Australian cropping systems - annual ryegrass, wild radish, brome grass, and wild oat. Beginning at the first opportunity for wheat harvest and on a weekly basis for 28 d afterwards the proportion of total seed production retained above a 15 cm harvest cutting height was determined for these weed species present in wheat crops at nine locations across the Western Australian (WA) wheat-belt. Very high proportions of total seed production were retained at wheat crop maturity for annual ryegrass (85%), wild radish (99%), brome grass (77%), and wild oat (84%). Importantly, seed retention remained high for annual ryegrass and wild radish throughout the 28 d harvest period. At the end of this period, 63 and 79% of total seed production for annual ryegrass and wild radish respectively, was retained above harvest cutting height. However, seed retention for brome grass (41%) and wild oat (39%) was substantially lower after 28 d. High seed retention at crop maturity, as identified here, clearly indicates the potential for HWSC systems to reduce seed bank replenishment and diminish subsequent crop interference by the four most problematic species of Australian crops.

Nomenclature: Annual ryegrass; Lolium rigidum Gaud. LOLKRI; wild radish; Raphanus raphanistrum L. RAPRA; wild oat; Avena fatua L. AVEFA; Brome grass; Bromus spp. Roth; BRODI; wheat; Triticum aestivum L.

La producción de semilla de malezas anuales, que persisten a lo largo de las fases de la producción de cultivos, repone/establece bancos de semilla viables a partir de los cuales estas malezas continuarán interfiriendo con la producción de cultivos. El control de semillas de malezas mediante sistemas de cosecha (HWSC) es ahora visto como un medio efectivo para interrumpir este proceso al enfocarse en semillas maduras de malezas, previniendo la entrada de nuevas semillas en el banco de semillas. Sin embargo, la eficacia de estos sistemas está directamente relacionada a la proporción del total de semilla producida que la especie de maleza retiene (retención de semilla) al momento de la madurez del cultivo. Este estudio determinó la retención de semilla de cuatro malezas anuales dominantes en sistemas de cultivos Australianos -Lolium rigidum, Raphanus raphanistrum, Bromus spp., y Avena fatua. Empezando en la primera oportunidad de cosecha de trigo, y siguiendo intervalos semanales durante 28 d, se determinó la proporción del total de la semilla producida que fue retenida sobre 15 cm (altura de corte de la cosechadora) para estas especies de malezas presentes en campos de trigo, en nueve localidades a lo largo de la faja de trigo en el oeste de Australia (WA). Proporciones muy altas de la semilla total producida fue retenida al momento de la madurez del trigo para L. rigidum (85%), R. raphanistrum (99%), Bromus spp. (77%), y

Michael J. Walsh and Stephen B. Powles "High Seed Retention at Maturity of Annual Weeds Infesting Crop Fields Highlights the Potential for Harvest Weed Seed Control," Weed Technology 28(3), 486-493, (1 September 2014).
Received: 17 December 2013; Accepted: 1 March 2014; Published: 1 September 2014

Herbicide resistance
seed bank
weed seed retention
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