by Emily Leeson
“We have to do anything we can to minimize the time soil is left bare without anything growing,” says Dr. Judith Nyiraneza, a research scientist with Agriculture and Agri-Food Canada (AAFC) based in Charlottetown.
Nyiraneza and Oyster Cove Farms of Hamilton, P.E.I., recently completed a two-year study that tested the performance of cover crops planted following the potato harvest.
Nyiraneza said that a variety of cover crop options can help producers better manage soil health and reduce the environmental impacts of soil erosion.
When soil erodes, the valuable topsoil is lost. As it is blown away by winds or washed away by rainfall, the quality of the soil decreases – ultimately resulting in lower yields and potentially higher costs for producers trying to remedy their soil’s decreasing productivity. Erosion also increases the potential for groundwater pollution as agricultural chemicals from the soil are swept into water sources.
Nyiraneza said several factors account for the high risk of erosion on P.E.I. While the humid climate and sandy soil set the stage, traditional farming practices also play a role. With more than 80,000 acres of potatoes grown on the Island each year, the aggressive production takes its toll on the land. Growers gearing up for a short window of spring planting tend to till in the fall, leaving the land exposed to the snowmelt of early spring. Even after the potato planting, fields are relatively bare for several more weeks until the crop fully develops. Oscillating periods of drought and intense rainfall worsen the erosion problem.
The two-year study tested the performance of Winter rye, Winter wheat, and Spring barley planted after the potato harvest.
Cover crops work in many capacities. They increase organic matter and available nitrogen in the soil, promote beneficial insects, deter weed growth, bring up deep-rooted minerals, and increase the soil’s moisture-holding capacity. Cover crop plant growth also protects against erosion from wind and water – holding the soil in place and protecting it against the impact of heavy rainfall and run-off.
“Soil particles are detached by rain impact, and if there is a slope they are transported to other places,” said Nyiraneza.
During the study, the researchers used splash pans in cover crop fields to measure the soil movement caused by raindrops and the soil’s vulnerability to erosion. They measured the amount of carbon and nitrogen in the soil and measured the nitrates in the soil at different times throughout the fall, spring, and summer.
“We also did analysis on the yield quality of Winter wheat and Winter rye the following summer,” said Nyiraneza.
All three cover crops – Winter rye, Winter wheat, and Spring barley – showed promise. “They decreased the risk of soil erosion and reduced the amount of carbon and nitrogen that would be lost in soil compared with no winter cover control,” said Nyiraneza.
Winter rye and Winter wheat were also able to recover quickly in the early spring, providing additional protection when the snow is melting and the risk of erosion is high. They also offer the potential of a second cash crop. The yields of Winter wheat ranged between 4.5 to 7.6 tons per hectare and Winter rye ranged from 3.2 to 5.1 tons per hectare.
With the initial two-year study complete, Nyiraneza is continuing the research as part of the Living Lab-Atlantic initiative and in partnership with fellow AAFC scientists Dr. Aaron Mills and Dr. Andrew McKenzie-Gopsill, and Ryan Barrett, research and agronomy specialist with the P.E.I. Potato Board.
“We are testing all kinds of strategies to keep the ground covered,” she said.
Instead of looking exclusively at seeding winter cover crops after the potato harvest, they are investigating the potential of seeding the field ahead of the harvest.
“After harvest, there is a short window,” said Nyiraneza. “However, there are growers who plant cover crops just a few days ahead of the potato digging, so that while they are digging, they cover the seed with soil and then it does germinate.”
“Today we are testing multiple species,” she said. “When you seed ahead of potatoes, you have more potential. You can use oats, radish, oats mixed with radish, or mustard mixed with radish. There are more possibilities when you seed a little bit earlier – late August or early September.”
