Dr. Andrew McKenzie-Gopsill

Dr. Andrew McKenzie-Gopsill is a firm believer in the need for research that is battle tested in Maritime conditions.

A weed specialist based at the Agriculture and Agri-Food Canada Harrington Research Farm; he is the lead scientist for two AgriScience research projects and supports others spearheaded by the Atlantic Grains Council. The AgriScience Program, funded by the Government of Canada under the Sustainable Canadian Agricultural Partnership, aims to accelerate innovation by providing funding and support for pre-commercial science activities and research that benefits the agriculture and agri-food sector and Canadians. The Atlantic Grains Council AgriScience project is improving grain and oilseed producer outcomes in Atlantic Canada through applied research that addresses local priorities like climate change mitigation, soil health, crop quality, and sector competitiveness. 

The first of Andrew’s research projects is aimed at determining the best method of using cover crops to improve maize production while the other focuses on ways to improve weed management in soybeans.

While maize is a commercial crop in many warmer climates, in the Maritimes, it is traditionally used for silage. Over the course of the three-year project, Andrew and his team of researchers in both Harrington and the Fredericton Research and Development Centre are examining the benefits of both intercropping and the use of cover crops in the maize rotation.

“Silage corn returns little to the soil, ” he explained. “A cover crop after harvest definitely makes sense in this region since the soil is essentially bare after the silage corn is harvested.”

Instead, the project began the first year looking for crops that were suited to a Maritime climate and would grow well under the silage canopy. The first year saw them test drive a wide range of grasses and legumes but, the second year concentrated on what he called “the top two by far”– annual ryegrass and the yellow sweet clover. Both crops have dense roots that help prevent erosion and catch excess nitrogen, as well as break up extremely compacted soil.

Andrew explained that the one valuable lesson learned in the first year of the experiment in 2023 was the importance of timing when planting the cover crop.  A wrong miscalculation could mean a reduction of yields of close to 50 percent– something no producer could accept. While using annual ryegrass did produce a slightly lower yield, on the plus side it offered better weed suppression. This spring, the field will be evaluated in terms of soil cover before another growing season.

The other half of the experiment incorporates sorghum-sudangrass in the rotation, an annual grass that has the same requirements as corn but uses half the nitrogen.  The rotation also includes crimson clover.

The experiment calls for varying nitrogen rates, 25 per cent was applied at planting with top dressing applied at five different rates ranging from zero to 125 per cent.  He explained the first year of the experiment saw sorghum and no cover crop control responded exactly as expected, namely an increased nitrogen rate resulted in a decrease in silage.

“When we go to clover, we see the exact opposite,” he explained. “Our highest biomass and our highest silage corn yield is zero nitrogen and those decline as you increase the rate. That was really a surprise, and it requires more work.”

The second corn crop will be planted in 2025, and he will be waiting to see if this year’s planting will produce similar results.  He explained the last phase of the project will be to take the most promising varieties of maize cover crops to on-farm agronomy trials in all three provinces in 2026 and 2027.

Turning to the soybean project, Dr. McKenzie-Gopsill explained the goal is to reduce the reliance of herbicide for weed management in soybeans.  He described an experiment with herbicide banding, where rather than broadcast applications herbicides are sprayed over the crop row only. In the Maritimes, soybeans are usually spaced 6 or 12 inches apart, with nozzle spacing at 18 inches.

“With that narrow spacing, you are not able to obtain any herbicide savings with banding,” he noted. “If you want to start herbicide banding your soybean crop, you have to go all the way up to 30-inch rows like corn.  With that wide row spacing you are able to drop your boom and apply herbicide in a narrow band over the row.

However, opening up the canopy means the soybeans will never reach full closure and there is more open space during the period of the growing season when yield can be impacted. The experiment uses fall rye and tillage radish as cover crops seeded between the rows rather than using herbicide or cultivation to suppress weeds. 

The research team uses four different herbicide treatments, namely a pre-emergence herbicide only, a post-emergence herbicide only, a combination of the two, and no herbicide. The first two years of the study indicate banding can reduce herbicide use by up to 73 per cent.

The fall rye has proven effective in reducing weeds, but the tillage radish interferes with the soybean, resulting in a slight yield reduction. He noted those results were consistent no matter what herbicide program was used.

“We also had the same plant population on our wide row soybeans as the narrow row,” he noted.

Another experiment involves using a no-till system, using a roller-crimper, to roll the cover crops in and then direct seed the soybeans. To terminate the fall rye with a roller crimper, it must be handled when it has committed to going reproductive.

“If it is terminated at that point, it will actually stay in the ground, but if it is terminated before, it has a tendency to pop back up,” he explained.

Recognizing not everybody has a roller crimper, he noted they are also looking at other ways to terminate the cover crop.

During the first year of the experiment, there is a major difference in the success rate between the crops in Fredericton and Harrington. While the New Brunswick crop had good rye growth, excellent weed suppression, and strong yields for the soybean crop, the picture was less rosy in Harrington.

“Our fall rye did terrible and barely established. It looks like we seeded a little bit too late,” he said. “This year, we seeded a little earlier and the fall rye looked better.”

The final experience with soybeans centres on the economics of spring and fall herbicide burn-downs. Rainwater in the Maritimes tends to have a lower pH and contains elements like iron, zinc and potassium and a lot of herbicides will bind to those ions. Dr. McKenzie-Gopsill explained most studies done on water hardness only focus on calcium and magnesium and pure water is used. This study used water and varied the water hardness from 30 parts per million (ppm) up to 180 ppm. He noted that water is in the range of 90-100 ppm. He noted the spring experiment responded as expected with more efficacy with softer water “whereas in the fall we saw the opposite where the higher rates were responding normally but the lower rates were doing the opposite where we got more efficacy with harder water. That will take a little more experimentation to figure out why.”