Using residual herbicides to enhance crop performance
It makes economic and agronomic sense to control weeds when they are germinating says Adama NZ Portfolio Manager Hamish Mulcock. This is achieved by using residual or pre-emergent herbicides following sowing and prior to crop germination.
“A seedbed may look clean, but that does not mean weed seeds are not present. Buried weed seeds delay germination until the soil’s moisture level and temperature are favourable for establishment. Additionally, some weed species can last in the soil for decades and often the process of cultivation brings these weed seeds closer to the surface where they can germinate,” explains Hamish.
Along with good soil preparation, residual herbicides aid in enhancing crop performance and establishment by providing effective, selective short to medium-term weed control. This removes the threat of early-season weeds so they are not competing with seedlings for nutrients, moisture, space, and light.
“To get the most out of residual herbicides, form a good seed bed,” says Hamish. “Spraying then creates a herbicide film on the soil that then incorporates after rainfall.”
Hamish says anything that prevents an even application wastes spray and reduces efficacy and/or the length of residual weed control. He says clods or large amounts of previous crop residues compromise spray coverage by creating pockets where weeds can get a foothold.
The timing and the amount of rainfall are vital for optimal weed control as they affect the herbicide’s ability to bind to the soil. Hamish says a light rain is best with 10 to 20 mm generally required to incorporate and activate residual herbicides following spraying. Irrigation is also useful, where available.
Following incorporation, residual herbicides take two to three days to bind to the soil and organic matter and reach a balance between what is bound to the soil and what soil water is available for uptake by germinating weeds.
Hamish says there are differences in soils and their abilities to bind to herbicides. Lighter, sandy soils have fewer binding sites which increases the risks associated with leaching losses and potential crop damage. Heavy clay, or high organic matter soils, have more sites that can tightly bind herbicides making them less available for weed update. High application rates may be recommended on these soils and some residual herbicides may not be suitable on a particular soil type.
Residual herbicides are commonly used for early-season weed control in high-value and time-critical crops including maize, fodder beet, cereals and forage brassicas. Among Adama's residual herbicide range are Ethosat® and Goltix® Gold, Acierto®, Atranex® and Mesoflex®.
Discover which Adama residual herbicide is most appropriate for the crops and soil types by contacting your local PGG Wrightson Technical Field Representative.
Registered pursuant to the ACVM Act 1997, Ethosat® #P008169, Goltix® Gold #P009741, Acierto® #P008861, Atranex® SC Herbicide #P007245, Atranex® WG Herbicide #P007464, Atranex® Flow #P009557, Atranex® WG #P009754 and Mesoflex® #P008494. Always read the registered label before use.
