Improve weed control with variable herbicide rates

Pre-emergence herbicides are effectively the only way to manage weeds in sorghum, because of a shortage of post-emergence options. Actives commonly used include atrazine and metolachlor.

However, these molecules can be tied up by soil particles, preventing them from being taken up by the weed’s roots. And this depends on soil type.

Garrison Gundy, weed scientist at Kansas State University, highlights that soils in Kanas can be very variable. Therefore, to maximise pre-emergence efficacy, a more targeted approach may be needed.

Self ropelled crop sprayer working on a drilled field. Photo credit: Tim Scrivener

Therefore, Gundy developed algorithms to enable the variable-rate application of two commonly used tank mixes using data created by the Veris machine. The soil analyser measures conductivity and soil organic matter content.

“The variable rate gave the same [weed] control as the flat rate, while at the same time reducing the amount used,” he concludes.

Dr Gundy was speaking at the recent European Conference on Precision Agriculture, held in Edinburgh. Also read other advice given at this conference:

• Variable rate fertiliser can slash N leaching into the Mississippi – David Mulla, researcher at the University of Minnesota
• ‘Farmer organisations have a key role in precision farming uptake’ – Neale Postlethwaite (Society of Precision Agriculture Australia)