Herbicide residues in sandy soils of the Southern region
Authors: Lynne Macdonald1, Rai Kookana1, Nigel Wilhelm2, Therese McBeath1, Rick Llewellyn1
Research Team: Barry Haskins3, Michael Moodie4, Adelle Craig1, Jun Du1
1CSIRO, Waite Campus, 2SARDI, Waite Campus, 3AgGrow Agronomy, Griffith, 4Mallee Sustainable Farming, Mildura
Funded By: GRDC Sandy Soils CSP000203
Project Title: Increasing production on sandy soils – overcoming constraints to poor water use
Peer Review: Lukas van Zwieten, Mick Rose
Key Words: herbicides, residues, sands, sandy soil
Key Messages
- A study of herbicide residues in sandy soils in the southern low rainfall region found Glyphosate and its breakdown product AMPA at all nine sampled sites.
- The combined residue load (Glyphosate plus AMPA, 0-30 cm) represented between 0.7 and 6.1 typical applications. The majority (~85%) of the herbicide residue was found in the top 10 cm, and was predominantly AMPA (~80%) rather than Glyphosate.
- Little is known of the toxic effects of AMPA and how it may affect root growth and function across different crop species. Identifying threshold levels of AMPA that negatively impact crop productivity would be valuable.
- The study detected Trifluralin (8/9 sites) and 2,4D (4/9 sites) at low concentrations unlikely to be damaging to crops. We did not detect Prosulfocarb, imidazolinones (Imazapic, Imazapyr, Imazamox), Triclopyr, or MCPA. Spray history details are being collated to further understand the Glysphosate results and assess whether non-detection of other herbicide residues is due to infrequent use or to breakdown.
