Sean Mason1, Glenn McDonald1, Bill Bovill2, Willie Shoobridge3, Rob Wheeler3
1 School of Agriculture, Food and Wine University of Adelaide; 2 CSIRO Land and Water, Canberra; 3 SARDI New Varieties Agronomy
• Yield responses to P were associated with promotion of early crop biomass in both wheat and barley. Compared to N, there appears to be less risk of high P rates adversely affecting yields.
• Compared to differences in yield among varieties, differences in responses to P have been small. At this stage variety selection should be based on potential yield rather than any differences in PUE to achieve the greatest return in investment from P.
• Phosphorus nutrition levels should be continually monitored especially those on replacement P programs and soil types with moderate to high PBI levels. Required P rates for both trials were at least double the calculated replacement P rates.
• More efficient replacement P rates could be obtained if they are adjusted in accordance with PBI levels if they vary significantly within a paddock.