Demonstration of reduced use of broadleaf herbicides in potato crops through chemical banding and mechanical cultivation in Quebec, Prince Edward Island, and New Brunswick

Project Code PRR10-120

Project lead

André Gagnon   ProgesT 2001 Incorporated

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 potato crops in Quebec, Prince Edward Island, and New Brunswick 

Summary of Results

Background 

The majority of potato growers rely on widespread broadcast applications of herbicides to control weeds. This results in the use of large amounts of herbicides and an increased risk of resistance development in weeds. Previous studies have shown that banded herbicide applications provide comparable weed control and potato yields as conventional broadcast applications. Herbicide banding, which consists in spraying chemicals only above the plant rows, results in a significant reduction in the amount of herbicide used. The herbicide is sprayed either at planting, pre-emergence or post-emergence, and the weeds between the rows are controlled through mechanical cultivation.

The goal of this project was to demonstrate the feasibility and advantages of using herbicide banding technology at the commercial scale, specifically in commercial potato fields in Quebec (QC), Prince Edward Island (PEI) and New Brunswick (NB).

Methods

In the first year of the project, the work involved planning, reaching agreements with the collaborators and participating farms in the three provinces, designing and building the kits required to modify the farm equipment (planters, cultivators, sprayers) for the herbicide banding treatment, preparing the test protocols and promoting the project.

The demonstration trials were carried out during the 2011 growing season on a total of 19 potato fields in the three provinces: 13 in QC, 4 in NB and 2 in PEI. The large number of sites allowed testing in a range of different conditions (soil, climate, cultivars and potato markets). Banded application of herbicide combined with mechanical cultivation was compared with the conventional broadcast application method used by farms. Demonstration plots covering at least two hectares of commercial fields were used.

Herbicide banding consisted of spraying only over the potato rows, covering a width of 46 cm (versus a width of 91.5 cm, including the space between the rows), which is about half of the area treated through broadcast spraying. The herbicide was applied pre-emergence, specifically at the growth crack stage, or early post-emergence, using a TeeJet Blue (8003EVS) or flat spray (60057) nozzle, at 40 pounds per square inch. One or more passes of the mechanical cultivator were made to treat the space between the rows, according to current practices and weed pressure. In conventional plots, only broadcast spraying was carried out. The herbicides Lorox, Gramoxon and Sencor were applied using the application rates specified on the respective product labels. Monitoring of weeds was done at 10, 20 and 30 days after the treatment, and the crop yield was measured to compare the effect of the herbicide banding and the broadcast treatments.

Results

Overall, the project testing herbicide banding combined with mechanical cultivation produced positive results, and this weed control method was found to be as effective as broadcast spraying. There was very little or no difference between the banding treatment and the broadcast treatment in terms of both weed populations and potato yield. For example, at the St-Paul, QC site, the total potato yield was 46.2 tonnes/hectare (t/ha) in the herbicide banding treatment compared to 48.2 t/ha in the broadcast treatment, whereas at the Mont-Carmel, QC site, the yields were 24.1 t/ha and 15.9 t/ha, respectively.

These trials showed that herbicide banding can reduce the amount of herbicide applied to plots by 50%. Since only half the area had to be treated, half the amount of herbicide was used in these crops, in spite of the fact that both treatments used the same application rate specified on the label. The herbicide banding technology combining chemical and mechanical weed control can result in savings for growers while reducing the pesticide loading to the environment and slowing the development of herbicide resistance in weeds.

There are encountered, however, issues associated with this approach: the predisposition of growers to reduce the number of passes with the mechanical cultivator (particularly growers in PEI), which appears to be incompatible with herbicide banding, as well as the difficulty of aligning the nozzles with the top of the hilled rows. The latter problem can be addressed by using a Global Positioning System to precisely control the path followed by the equipment. Herbicide application at the time of planting (nozzles installed on planter) or during mechanical cultivation (installed on cultivator/row shaper) can also help to overcome these two issues.

More than 25 growers and sector stakeholders were directly involved in the on-farm demonstration trials, which covered nearly 50% of the total area planted to potato in Canada. Several information and demonstration days were held during summer 2011 at different sites in QC, NB and PEI, to communicate the project results to producers, agronomists, technicians and government and private sector representatives in the regions concerned. In general, the growers were very satisfied with the observed outcomes at all the sites. The herbicide banding method has therefore proven its effectiveness and represents a suitable option enabling growers to reduce their pesticide use.

For more information about this study, please contact André Gagnon.

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