Dr Craig Scanlan1,2,3, Dr Raj Malik4, Dr Gustavo Boitt2,6, Dr Mark Gherardi5, Mr James Eason6, Professor Zed Rengel2
1Department Of Primary Industries and Regional Development, Northam, Australia, 2The University of Western Australia, Crawley, Australia, 3SoilsWest, Murdoch University, Murdoch, Australia, 4Department Of Primary Industries and Regional Development, Katanning, Australia, 5Summit Fertilisers, Kwinana Beach, Australia, 6CSBP, Kwinana, Australia
Biography:
Craig Scanlan has worked on nutrient management in grain production for 20 years. Craig's work has focussed on nitrogen, phosphorus and potassium nutrition, and how the management of soil constraints influences the availability of these nutrients. His recent work has focussed on climate effects on crop response to fertilisers. Craig is a Principal Research Scientist with the Department of Primary Industries and Regional Development.
Abstract:
The context for phosphorus (P) fertiliser decisions has changed since most of the field-based research for P was done in Western Australia (WA). Long term positive P balances in WA cropping systems have led to an accumulation of soil P. Also, cropping intensity has increased, the percentage of legume crop area has decreased and near-complete adoption of no-till has occurred in the last three decades. We assessed which soil and climate factors had the greatest influence of wheat yield response to fertiliser P using a recent (2018-2021) set of 40 field trials in WA. The sliding window approach was used to examine whether total rainfall within time-based windows was related to wheat response to fertiliser. Relationships between soil properties, rainfall and yield response were also assessed using regression modelling. Our analysis revealed that for soils where PBI (0-10 cm) was less than 50 (low PBI soils), grain yield response to P fertiliser was related to rainfall in a 4-week period before sowing. Overall, the greatest yield responses occurred where less than 8 mm of rain fell in this period. However, when rainfall was greater than 8 mm, pH was an important factor; yield response was greater when soil pH (0-10 cm) was <5.1, compared to sites where soil pH was ≥5.1. The rainfall-yield response relationship identified in this work provides a basis for a tactical response of P application at sowing to rainfall conditions leading up to this operation. Future decision support systems should include the effect of rainfall prior to sowing on low PBI soils to allow the economic payoffs from different strategies to be assessed.