1. Fertilizer and Lime Research Centre; Massey University; Private Bag 11222 Palmerston North 4442 New Zealand
2. School of Agriculture, Food and Wine; University of Adelaide; Adelaide SA 5005 Australia
3. NSW Department of Primary Industries; Elizabeth Macarthur Agricultural Institute; Menangle NSW 2568 Australia
4. Department of Agricultural Science; LaTrobe University; Bundoora VIC 3086 Australia