Grazing of cereal crops reduces canopy light interception and could potentially reduce biomass production and grain yields. Alternatively, defoliation after canopy closure may increase light penetration and enhance radiation-use efficiency (RUE, shoot dry matter produced per unit light intercepted). Changes in dry matter partitioning following grazing may also ameliorate grain yield penalties. Experiments with rainfed winter wheat were conducted near Canberra, Australia, to investigate the effect of different intensity or duration of grazing on two cultivars. Grazing reduced leaf area index (LAI), light interception and growth rates by up to 90% but did not affect overall RUE. Although grazing caused significant reductions in cumulative light interception and total dry matter accumulation, it did not affect grain yields because grazed crops had delayed phenological development, allowing increased partitioning of shoot dry matter to spikes. Grazing reduced stem dry matter accumulation and consequently decreased the amount of stem assimilate available for retranslocation to kernels by up to 75%. However, by delaying crop ontogeny, grazing prolonged green area duration after anthesis and thereby increased the supply of assimilates from current photosynthesis to developing kernels, mitigating potential yield penalties caused by defoliation. © CSIRO 2011.

Item Type:	Refereed Article
Keywords:	allometry; assimilate; defoliation; herbivory; kernels; phenology; physiology; retranslocation; Triticum aestivum.; allometry; crop yield; defoliation; dry matter; grazing management; herbivory; leaf area index; light effect; light use efficiency
Research Division:	Agricultural and Veterinary Sciences
Research Group:	Agriculture, Land and Farm Management
Research Field:	Agriculture, Land and Farm Management not elsewhere classified
Objective Division:	Plant Production and Plant Primary Products
Objective Group:	Winter Grains and Oilseeds
Objective Field:	Wheat
UTAS Author:	Harrison, MT (Dr Matthew Harrison)
ID Code:	84643
Year Published:	2011
Web of Science® Times Cited:	12
Deposited By:	Tasmanian Institute of Agriculture
Deposited On:	2013-05-23
Last Modified:	2013-06-06
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