Pilar Muschietti-Piana12, Therese McBeath12, Vadakattu Gupta1, Ann M. McNeill2, Bill Davoren1, Willie Shoobridge1
CSIRO Agriculture and Food1, The University Adelaide2
Peer review: Marianne Hoogmoed
Key Words: nitrogen, N, lupin, stubble, fertiliser, wheat production, yield, sands, sandy soils
- Without N fertiliser, wheat following lupins yielded more than double continuous wheat (1.7 vs 3.6 t/ha). A further 27 % yield increase (4.9 t/ha) was achievable when 40 kg N/ha was added to wheat following lupins.
- Increasing N fertiliser inputs on a wheat crop following legumes can improve crop performance and N uptake.
- The mineralisation potential of N in a sandy soil is improved by including lupin in the crop sequence and increased N fertiliser inputs to wheat crops.
- Net N mineralisation over the fallow following lupins can be as high as 32 kg N/ha in a Mallee sandy soil.
Why was the trial done?
The nitrogen (N) supplied to crops, either through fixed N in legume residues or N fertiliser inputs, are critical to support or increase productivity on sandy soils. Previous experimentation in 2015 on Karoonda sands during a dry season (decile 3) demonstrated that a high rate of N fertiliser (40 kg N/ha) applied to wheat at sowing after lupin stubbles increased wheat biomass production and N uptake at advanced crop stages and improved yield potential.
As part of a PhD project (funded by GRDC project CSP00186) we conducted experiments on a sandy soil (0.5 % w/w organic C to 10 cm depth) to better understand the timing of the soil N supply capacity relative to wheat N uptake at key growth stages. We tested contrasting crop stubble treatments and N fertiliser inputs and assessed their effects on wheat productivity.
How was the trial done?
In 2016 we tested a combination of N input strategies including stubble treatments (cut/removed, wheat, or lupin) and fertiliser N rates (low, medium, or high) that can improve wheat productivity on a sandy soil. This involved intensive sampling and analysis of stubble, wheat plants and soil at key points during the fallow and in-crop on 36 plots with replicated treatments at a field in Lowaldie, near Karoonda.
We thank the Loller family for hosting the field site, Maxime Salot, Damian Mowat, Navneet Aggarwal, Stasia Kroker, Mathew Williams, Ahsan Chowdhury, Thomas Carter & Bruce Hawke for technical assistance, and the financial support by Australia Awards Scholarship. This research is funded by GRDC project ‘Stubble Initiative Module 1’ (CSP00186).