Do differences in yield components explain poor grain yield responses to Phosphorus fertiliser?

K Dunsford12, R Armstrong1 & R Launder3

1 Agriculture Victoria, 110 Natimuk Road, Horsham, VIC, 3400,

2 La Trobe University, 5 Ring Road, Bundoora, VIC, 3086

3 PB Seeds, 1324 Blue Ribbon Road, Kalkee, VIC, 3401


Early vegetative responses of wheat to phosphorus (P) fertiliser often diminish by grain maturity but the underlying causes of this change are not well understood. A field trial which was conducted on a Vertosol, with a low available P concentration, in the Victorian Wimmera, examined the growth of wheat (cv. Emu Rock) in response to applications of different P fertilisers. Normalized Difference Vegetation Index (NDVI), a proxy for aboveground biomass, responded to some of the P fertiliser products during stem elongation. A subset of treatments were sub-sampled to investigate whether this early responsiveness of wheat to P fertiliser was maintained through to grain maturity as well as gain more detailed information on changes to yield components. Phosphorus fertiliser had no significant impact on biomass, grain yield or harvest index, despite the early vegetative responses. Changes in the yield components suggest that the increased yield potential resulting from P application was not realised and the cause for this may be inadequate soil water supply during the latter part of the growing season.


The Australian Society of Agronomy is the professional body for agronomists in Australia. It has approximately 500 active members drawn from government, universities, research organisations and the private sector.

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David Marland Photography Southern Farming Systems Agriculture Victoria

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