Demonstration of reduced use of herbicides in carrot crops through chemical banding and mechanical cultivation in Prince Edward Island (PEI)

Project Code PRR10-080

Project Leads

Kevin Sanderson & Aaron Mills   Agriculture and Agri-Food Canada

Objective

To transfer and promote the adoption of herbicide banding technology as an integrated weed management approach that reduces the use of herbicides in commercial carrot production in PEI

Summary of Results

Background

Conventional weed control in carrot production uses a broadcast approach to herbicide application, in which the entire carrot field is blanketed with herbicide up to two times during the growing season. Previous research work demonstrated that applying a narrow band of herbicides along the top of carrot rows combined with mechanical weed control between the rows can decrease herbicide use by up to 66% compared to broadcast application while maintaining similar levels of weed control and yield. See the published factsheet called Banded Herbicide Application in Carrot Production. This technology, known as “banding”, can significantly reduce the impact of pesticides on the environment and the development of weed resistance to herbicides, and can also lead to savings for the producer due to lower input costs.

The goal of the current project was to validate the efficacy of herbicide banding in commercial field conditions, to demonstrate the economic and environmental benefits of banding technology to growers, and to show them how to incorporate this method into their production systems.

Approaches

The study was conducted by AAFC scientists at the Crops and Livestock Research Centre near Charlottetown, Prince Edward Island (PEI). Two commercial farm demonstration sites were established in the carrot producing region of PEI during the 2010 and 2011 growing seasons. Commercial spray equipment was retrofitted with new flat fan nozzles that were positioned to spray directly over each carrot row. The banding was implemented by applying a 30 cm wide herbicide (Linuron™) band on top of the carrot rows, which were spaced 90 cm apart, at both pre- (1.24 l/ha) and post-emergence (2.47 l/ha). Mechanical cultivation with S-tines and side-knives was used in combination with banding to remove the remaining weeds between the carrot rows and from both sides of each row, respectively. A total of four cultivation passes were used during the 2010 season (two with S-tines, two with side-knives). In an effort to keep inputs to a minimum, only two passes were used for the 2011 season (one with S-tines, one with side-knives). The timing of weed management was dictated by weed pressure.

Herbicide banding was compared to conventional broadcast weed control using both pre- (1.24 l/ha) and post-emergence (2.47 l/ha) applications of Linuron™. Note that while application rates were the same for the two treatments, banding sprays covered only one third of the surface area that broadcast sprays did, thus reducing the total amount of herbicide used per unit area by two thirds (i.e. 0.42 vs 1.24 l/ha, and 0.82 vs 2.47 l/ha in pre- and post-emergence applications, respectively).

Weeds were sampled and measured two weeks following the last cultivation to assess weed pressures and herbicide efficacy within each treatment. Carrots were harvested from all sites within a 3 m section from each plot and graded. Total and marketable yields were also measured for each treatment.

Results

Overall results from these commercial field demonstrations were consistent with those obtained from previous experimental work. Despite the differences in mechanical cultivation, results from the two growing seasons were not significantly different and the data were pooled for subsequent analyses. There were no differences between the banding and broadcast herbicide treatments in terms of either total biological yield or marketable yield. Medium sized carrots under the banded spray treatment had an increased average marketable weight and number when compared to the broadcast herbicide application. The mean weight of smaller sized marketable carrot roots was higher for those grown using the banded technology than with the broadcast herbicide application method. Overall, there were more unmarketable carrot roots and higher number of small unmarketable carrot roots in the conventional herbicide treatment group compared with the banded herbicide technology group. Weed pressures were manageable across sites using herbicide banding and within-row cultivation.

Cost benefit analysis demonstrated that herbicide banding can be economically as well as environmentally feasible for the average producer to consider implementing in their operation. It is important to note that while increased mechanical cultivation carries additional costs, cultivator passes can be kept to a minimum by installing the S-tines and side-knives together in tandem, in which case a single pass may suffice to control weeds between the rows. Therefore, when comparing the amount of herbicide used for broadcast spraying and factoring in the increased cultivation costs associated with banding (using the single tandem pass scenario), a producer can still save up to $9.00/ha by using herbicide banding. There is also an additional capital cost of retrofitting the existing sprayer boom with new flat fan nozzles (estimated at $9.00 per nozzle) to enable banding.

An open field day was hosted in mid-season during each study year to demonstrate the banding technology and its benefits to several producers, industry members and researchers from PEI and Nova Scotia. There was strong interest in this technology and positive feedback was received from attendees at each of the field days.

As the economics of herbicide banding technology combined with environmental concerns and herbicide resistance issues become more prevalent, this method provides a useful management tool for producers without compromising crop quality and yield potential. Crops grown with a reduced environmental footprint may provide a marketing niche for producers. This technology could be easily adaptable to conventional carrot crops grown on flat ground or in raised beds, as well as to organic carrot operations as registered weed control products approved for organic production become available in Canada.

This project is part of the Pesticide Risk Reduction Program’s action plan to implement a reduced-risk strategy for integrated weed management in field vegetables. For more information about this study, please contact Aaron Mills.

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