Several environmental and soil properties impact the effectiveness of pre-emergence herbicide programs. In addition, chemical characteristics and combinations of herbicide products also influence weed control performance.
These properties, coupled with the frequent and high precipitation across most of Iowa in spring 2024, may have caused a breakdown in early season herbicide programs.
Early breakdown of pre-emergence herbicides generally leads to a higher weed presence during the growing season.
Historically, corn and soybean growers manage these weeds through timely post-emergence herbicide applications when field conditions permit.
To date, these post-emergence herbicide applications have been broadcast applications across the entire field, which have proven to be successful but can come with a high chemical cost.
Newly developed precision spraying technology allows applicators to precisely spray only the emerged weeds while reducing the volume of herbicides applied and associated chemical costs.
Several companies, including the joint venture of BASF and Bosch, John Deere and Greeneye Technology have brought precision spraying technologies to market.
These technologies allow the shift from a broadcast or blanket application to a precise and selective application. This allows chemistry to be applied only where it’s needed and avoids wasteful herbicide application in unneeded areas.
These sprayers are equipped with camera systems that have diverse capabilities. Entry-level systems provide “green vs. brown” capabilities, which will detect weeds (green) in fallow fields (brown soil or residue).
In Iowa this technology would be applicable to pre-emergence spraying of contact herbicides in no-till or strip-till management practices.
More advanced systems provide “green vs. green” capabilities, which will differentiate weeds from surrounding desirable crop and only spray weeds.
In either situation, weeds are detected in real-time and immediately sprayed.
Trade names for these precision spraying technologies vary, but generally terms like “See and Spray,” “Selective Spray” or “Smart Spray” are used to describe this new class of precision spray equipment.
Adjusting practices
In addition to including cameras along the boom for detecting individual weeds, additional technologies or changes to current spray practices are required to implement these precision spraying systems including:
- Boom height control: Precision spray technology requires consistent boom height control to keep the cameras and boom at a stable height above the ground.
- Vehicle speed: Precision spray technologies generally have a vehicle speed limitation between 10-15 mph, depending on the manufacturer.
- Maximum speed has been increasing over time as manufacturers continue to improve precision spray technologies, but today it remains below the maximum application speed for broadcast application.
- Individual nozzle control: Precision spray technologies generally require individual nozzle control. Cameras mounted along the boom will command individual or groups of nozzles to turn on to apply herbicide to the target weeds.
- Compatible nozzles: Specific nozzles are required to support precision spraying application based on manufacturer and herbicide product requirements.
- Boom recirculation: With the significant variability in the number of individual nozzles that are on at any point in time, boom recirculation is recommended to help maintain consistent herbicide coverage during precision spray applications.
Click here to see more...