Case Studies

Outliers skew P calibrations: wheat study

Mark Conyers (3) (002)

Outlying factors could be influencing phosphorus (P) requirements under Australian wheatfields, according to NSW research.

Scientists from NSW DPI, Murdoch University and the University of Queensland’s School of Agriculture and Food Science explored the variation between soil-available P (called Colwell P) and wheat yield by examining field-based factors.

Lead researcher Mark Conyers said: “Calibrations developed from the Australian Better Fertiliser Decisions for Crops database – the biggest dataset available – have been criticised, and so we aimed to explore factors accounting for more of the variation.”

Studying the dryland, winter-dominant rainfall region of southern NSW, the researchers found soil type was an important factor, as was an area’s tendency for dry conditions at sowing or during the season, indicating increased reliance on fertiliser P over P already in the soil. A similar trend was evident for a later sowing date, again suggesting an increased probability of crop P requirements being met from the fertiliser P.

Dr Conyers said: “It is possible to tighten the response curve for Colwell P and wheat by restricting the data for a given soil type and to ideal seasonal conditions. However, the outliers that are excluded frequently reflect an important subset of environmental conditions.”

Source: Crop and Pasture Science 71(2) 113-118

Featured Image: Dr Conyers