Vadakattu Gupta1, Therese McBeath1, John Kirkegaard2, Alan Richardson2, Jonathan Sanderman1, Stasia Kroker1, Steve Szarvas1, Bill Davoren1, Claire Browne3 and Rick Llewellyn1
Peer review: Margaret Roper, CSIRO
In low fertility agricultural soils of Southern Australia, crop residues are one of the major sources of carbon (C) for soil biota in low fertility agricultural soils of Southern Australia. As a result, stubble retention can provide benefits through changes in soil physical, chemical and biological properties. However, the selection of stubble management strategy could have a significant impact on the potential benefits to be gained from the activity of soil biota in their role in carbon turnover, nutrient mineralisation, and subsequent availability of nutrients to crops.
• The 2014 wheat crop at Karoonda had a harvest index of 0.4 and fertilizer N recovery was 35%.
• Wheat stubble from the 2014 crop contained 16 kg N/ha and had a C:N ratio of 95 which is common for cereal crop residues in these environments .
• Mineralization during summer resulted in the accumulation of 18-33 kg/ha of mineral N to 50cm depth across all the treatments at sowing in 2015.
• Incorporation of 2014 cereal stubble increased microbial biomass and N supply potential at sowing in the surface soil when compared with standing stubble.
• The management of cereal stubble affects the microbial activity that influences the cycling and supply of nutrients (nitrogen (N) and phosphorus) to growing crops.
• There was no significant effect of management of 2014 stubble on subsequent wheat grain yield in 2015.