Potatoes in Canada

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How farmers in P.E.I. deal with soil erosion and disease

February 20, 2024  By Farmers Weekly

Elizabeth Irving, who runs Indian River Farms alongside her grandfather and mother, describes P.E.I.’s iconic iron-red, fine sandy loam soils – common to large parts of the province and ideal for growing potatoes – as the business’ prize asset.

But, the Island’s undulating topography and maritime climate present a major threat to its sustainability.

As reported by Adam Clarke in Farmers Weekly, on average, the Island serves up more than 1,000mm of annual rainfall, harsh winter freeze-thaw cycles and stubbornly high winds from month to month.

“My first thought when asked about my greatest challenge always turns to soil erosion.

“We invest so much into our soils and if you lose it, that investment goes with it, too. It’s something we’ve been working hard to manage,” she explains.

Concern for soils

Soil degradation has long been a concern for the Island’s administration, with long-term studies over recent decades showing a steady reduction in organic matter in intensive arable areas.

In 2001, some 40 per cent of P.E.I.’s potato crops were grown in less than one in three rotations, making tillage frequent and intense, while declining livestock numbers have deprived many farms of vital organic matter and nutrients to return to soils.

The resulting lower water holding capacity and a trend to less frequent, but more intense rainfall events present significant erosion risk to exposed soil, and where soil compaction is also a factor, such as after harvesting potatoes in a wet autumn, risk is even greater.

There is a knock-on effect on the island’s water quality, with sediment and nutrients potentially all ending up in groundwater.

Action has been taken by the P.E.I. government to encourage adoption of practices designed to combat the problem, with financial incentives on offer.

Elizabeth says historical measures have included berms, buffer zones and grassed waterways, with Department of Agriculture-funded software helping farms design and layout these measures for maximum environmental benefit.

Berms reduce the velocity of water flow or direct it to areas that are not susceptible to erosion, subsequently reducing adverse effects on running water on exposed topsoil.

Hay mulching, whereby a hay crop is grown and baled before spreading on to potato fields post-harvest to slow down surface run-off, is another practice encouraged to mitigate erosion.

Lastly, strip cropping, where a variety of crops are established in alternating strips in a single field helps reduce erosion, especially on sloping land.

Changing ways

More recently, the Living Laboratories Initiative has connected farmers, researchers and other industry stakeholders to co-develop and test practices and technologies to protect soil and water quality.

These initiatives have prompted Indian River Farms to change some of its agronomic practices, with the major tweaks including cultivation timings and the introduction of cover crops where possible.

According to the latest Canadian government farm census, P.E.I. farmers are now the most likely of all provinces to plough down cover crops, with 29.2 per cent saying they use green manures, compared with just 8.6 per cent nationally.

Furthermore, 21.9 per cent say they establish a cover crop to protect soil over winter, which is double the national adoption rate of 10.7 per cent.

“We don’t do any fall tillage now and we were trying to broadcast a green cover after potato harvest, depending on the season.

But past 15 October, it usually gets too cold for anything to germinate and establish other than slowly, so it isn’t easy,” says Elizabeth.

Early dying complex

The introduction of cover crops has also been driven by tackling the business’ most significant crop health challenge, potato early dying complex (PED), which is one of the most economically damaging issues for North American potato producers.

Root lesion nematodes interact with fungi such as verticillium dahlia – the main causal agent of verticillium wilt – resulting in disease complexes that exacerbate damage to potato crops.

Both pathogens and pest can act alone to limit yield in potato crops if present at high enough levels, but when the two work together, the impact can be devastating.

It is thought that other pathogens such as Rhizoctonia solani and black dot can contribute to the PED complex, which affects plant health well before crop maturity, reducing bulking and marketable yield.

Initially, lower leaves die, then stems and, in severe cases, stem end vascular browning is seen in tubers.

Verticillium wilt is favoured by moist, lighter texture and warm soils and tends to occur most frequently in wetter, low-lying areas of fields such as sprayer wheelings and machinery entrance points.

Wetter soils are thought to promote shallow root growth, and this tends to accelerate foliar senescence caused by PED.

Management of verticillium during the growing season is limited to optimising nitrogen and phosphorus rates which reduces – but does not eliminate – the severity of wilt symptoms.

For susceptible variety Russet Burbank, Indian River Farms is boosting its nitrogen nutrition with an additional weekly 2-3kg/ha of N in foliar urea (20 per cent N) form, added to fungicide applications.

“Other environmental stresses such as drought also contribute to the problem.

“We’re trying to get a handle on the effects of all the crops in our rotation on nematode populations, as it’s by far our biggest constraint on yield.

“When a field goes down in August before the crop matures, it really is sad to see,” says Elizabeth.

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