Do spring cover crops rob water and so reduce wheat yields in the northern grain zone of eastern Australia?
J. P. M. Whish A D , L. Price B and P. A. Castor CA CSIRO Sustainable Ecosystems, Agricultural Production Systems Research Unit, PO Box 102, Toowoomba, Qld 4350, Australia.
B QLD Department of Primary Industries, Toowoomba, Qld 4350, Australia. Current address: Northern Grower Alliance Inc., PO Box 78, Harlaxton, Qld 4350, Australia.
C Michael Castor and Associates, 58 Marshall St, Goondiwindi, Qld 4390, Australia.
D Corresponding author. Email: jeremy.whish@csiro.au
Crop and Pasture Science 60(6) 517-525 https://doi.org/10.1071/CP08397
Submitted: 6 November 2008 Accepted: 31 March 2009 Published: 12 June 2009
Abstract
During the 14-month-long fallow that arises when moving from summer to winter crops, stubble breakdown can denude the soil surface and leave it vulnerable to erosion. Cover crops of millet have been proposed as a solution, but this then raises the question, how often is there sufficient water in the system to grow a cover crop without reducing the soil water reserves to the point of prejudicing the following wheat crop? An on-farm research approach was used to compare the traditional long fallow (TF) with a millet fallow (MF) in a total of 31 commercial paddocks over 3 years. Each treatment was simulated using the simulation-modelling framework (APSIM) to investigate the outcomes over a longer timeframe and to determine how often a millet fallow could be successfully included within the farming system.
The on-farm trials showed that early-sown millet cover crops removed before December had no effect on wheat yield, but this was not true of millet cover crops that were allowed to grow through to maturity. Long-term simulations estimated that a spring cover crop of millet would adversely affect wheat yields in only 2% of years if planted early and removed after 50% cover had been achieved.
Additional keywords: simulation modelling, fallow management.
Acknowledgments
We thank the staff of Michael Castor and Associates (MCA), Agricultural Consultants, Goondiwindi and their farmer clients, and technical staff of CSIRO Toowoomba and Queensland DPI who participated in this project. We also acknowledge the financial support of GRDC through the eastern farming systems project, MCA Goondiwindi, Queensland DPI, and CSIRO.
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