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Five-year study could hold key to reversing declining potato yields

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Media Relations
Agriculture and Agri-Food Canada

Declining soil quality and widespread presence of soil-borne diseases are the two major factors influencing yield limitations in Canada’s potato growing regions according to Dr. Bernie Zebarth, an Agriculture and Agri-Food Canada (AAFC) soil scientist. At the conclusion of a five-year, industry-led study looking at declining potato yields, Zebarth says improving potato cropping systems will go a long way in increasing soil quality and suppressing pathogens.

In 2013, potato industry stakeholders engaged with AAFC research scientists including Zebarth, as well as provincial and academic collaborators to help understand the causes of declining yields and find out if the trend can be reversed.

"Potato production is hard on soil quality. Frequent tillage, short potato rotations and soil erosion can all reduce soil organic matter, and the potato crop adds little organic matter back to the soil. When soil quality is low, the potato crop suffers because there’s less aeration and biological activity, and soils don’t have the same capacity to hold water or take up nutrients. Poor soil quality can also reduce drainage, and in wet spring weather can result in poor early growth or seedpiece rot."

- Dr. Bernie Zebarth, Research Scientist, Agriculture and Agri-Food Canada

Researchers looked at a variety of methods to enhance soil quality including compost, nurse crops and fall cover crops. These methods were shown to enhance soil quality by increasing and preserving organic matter. However, better soils didn’t necessarily result in increased yields in the short term.

Scientists were surprised to discover that soil-borne diseases have a much larger impact on potato yields than previously thought. The main culprit is the Potato Early Dying (PED) disease complex.

PED is caused by the fungal pathogen Verticillium dahliae which causes Verticillium wilt. When root-lesion nematodes are also present, this makes a devastating combination for potato plants and can cause substantial yield losses. Zebarth says there is some evidence that PED symptoms can be minimized in healthy soils.

"Better cropping systems and good agronomic practices can help suppress soil-borne diseases, and at the same time build healthy soils. When soils are healthy, the micro-organisms may be able to better compete with the pathogens and can lessen their impact on the crop."

- Dr. Bernie Zebarth, Research Scientist, Agriculture and Agri-Food Canada

Zebarth says this study has served to identify the major barriers to reversing declining potato yields and given scientists and industry a path forward toward finding solutions. He added that this work has shown developing new cropping systems that both build soil quality and suppress soil-borne pathogens is one of the best ways improve potato yields in Canada.

Moreover, the study has paved the way for new research into better understanding these soil-borne pathogens and how they behave; developing new diagnostic tools and developing practical management strategies.

Key Discoveries

Photo gallery

Man kneeling in a field of potato plants.
AAFC research scientist Dr. Bernie Zebarth
Farm plot of tall, green mustard plants with yellow blooms.
These mustard plants are being tested by AAFC researchers as a rotational crop species to increase soil health and suppress soil-borne diseases in potato rotations

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