Objective
- To identify kochia using image based methodologies.
- To determine the degree in which soil salinity influences kochia density, plant size, and abundance within a field.
- To determine if the identification of kochia using UAV imagery can be scaled up using high resolution satellite imagery, enabling this technology to have much broader use for the industry.
- Identify the potential to use salinity based data to develop management systems for spatially explicit weed management systems for kochia and eliminate “seed nurseries”.
Project Description
Kochia is becoming one of the most problematic broadleaf weeds on the Canadian Prairies because of its ability to rapidly evolve resistance to different herbicide sites of action. Most recently, three-way resistance (Group 2, 9, and dicamba (4)) has been found in 10% of the kochia populations in Alberta. Standard ways of controlling kochia have largely failed as it has fast becoming the most problematic weeds on the prairies.
Kochia is a halohyte plant and is found on much of the saline lands on the prairies. In addition, some kochia species appear to be somewhat unique in that it has a type of C-4 photosynthesis that actually requires sodium as a micronutrient. This may explain recent observations of kochia weed experiments that often find it is difficult to establish in non-saline soils research land. We believe that the large competitive advantage that kochia has in saline areas of the field when compared to the crop. As a result of this saline areas are often have little crop growth to compete with the kochia. We believe that kochia seed produced in these areas acts as the source for entire adjacent areas in the field and that by eliminated these “kochia nurseries” we could dramatically reduce kochia in the entire field.
Kochia has been found to have a relatively short seedbank longevity with greater than 95% of seeds persisting for less than 2 years. Kochia is both drought and saline tolerant. Precipitation during 2010 to 2017 was generally above normal for most of the Canadian Prairies, resulting in rising water tables and the appearance of saline patches. These saline patches which often ring wetlands (sloughs) have become a source for kochia plants. In a preliminary study conducted on USask land we utilized Unpiloted Aerial Vehicles (UAVs) to image the location of kochia plants in an area with salinity issues. We then mapped the salinity, topography, and hydrology. Preliminary investigation clearly indicated the locations of the highest densities of kochia had the highest salinity and lowest elevation associated with sloughs. Many of these areas are too saline to support annual crop growth allowing kochia to grow without crop competition. When herbicide is applied to these areas the selection pressure for herbicide resistance is extremely high. We believe that if kochia could be managed in these source “seed nurseries”, this would greatly alleviate the problem on those areas of the field where a productive crop can be grown. The limited mapping that we did indicated that kochia densities were extremely low in areas of low salinity and higher elevations. The mapping would be used to identify the percent of the field infested with kochia, and ultimately determine if practical site-specific recommendations could be developed to manage the areas with the highest kochia densities (seed nurseries).
The hypothesis of this project is that kochia infestations is primarily limited to those areas of the field with the highest levels of salinity. If seed production of kochia is controlled in the saline seed nurseries this will both reduce the selection for new herbicide resistance as well as the overall population in the field. To test this hypothesis, we need to first determine if we can distinguish kochia from crops in the field using digital imagery. Secondly, we would establish the association of kochia with saline areas and topography in the field. Following this we can isolate these locations and determine if site-specific recommendations could be employed by a grower that would minimize interference with their normal field operations.
