Every spring, I have some producers share soil test results with me as we discuss crop rotation, variety choice, and fertility programs.
While those traditional soil tests are very useful and underpin any good 4R fertility program, there are other sources of data which may be useful to help overcome some of the more common factors that limit yield in potato production. In this article, we explore some of these factors.
Soil Compaction
Compaction is not always the most obvious yield limiting factor in many fields, but I would argue that it is one of the single biggest yield robbers we face. Equipment is getting larger as farm sizes grow and available operators are harder to find. Potatoes require soil disturbance, often at times when we would rather not be on the land, like during fall harvest. Heavy equipment on wet soil is a recipe for soil compaction. Freezing and thawing soil over winter as well as tillage can help mitigate surface compaction, but deeper compaction is harder to remedy… if it can be remedied at all!
Some simple recommendations to measure and reduce compaction include:
- Limit traffic on fields when soil is saturated. Drier soils are less vulnerable to compaction than wet soils.
- Controlled traffic in fields. Most of the potential compaction occurs on the first trip across the field, so it is better to concentrate your traffic on the smallest area of your field as possible. This is particularly important during harvest… keep trucks on designated paths through the field.
- Use central tire inflation systems, particularly for bulk trucks. Operating trucks in the field at tire pressures that you would use for the road is a recipe for serious compaction.
- The more axles the better. Spreading weight over more axels will reduce deep compaction.
- Investigate compaction-fighting crops like alfalfa, sorghum sudangrass or daikon (tillage) radish.
- Measure it! Get a soil penetrometer and measure it yourself. PSI greater than 300 under moist soil conditions indicates significant barriers to root growth.
Early Dying Complex
The challenges posed by potato early dying (PED) complex are not new for Canadian potato growers; however, the incidence of Verticillium wilt, often in combination with other diseases, is rarely uniform across fields or even within fields.
An effective management strategy for early dying should include soil sampling for Verticillium dahliae and root lesion nematodes to determine what levels of inoculum are present on a field-by-field basis. Elevated levels of either of these pathogens can then inform management decisions, such as changing up your crop rotation to include a disease suppressive crop, lengthening your crop rotation, choosing a more resistant variety, or using a soil fumigant or in-furrow pesticide.
Some key findings from the CanPEDNet project under the last National Cluster confirmed that Western Canada doesn’t appear to have Pratylenchus penetrans nematodes (a key culprit in PED), but does have a relatively aggressive strain of Verticillium dahliae. In Eastern Canada, it was important to find out that not all root lesion nematodes are P. penetrans, but they are present in about 40 per cent of surveyed fields in New Brunswick and P.E.I. As the old adage goes, we must know our enemy if we are to fight them effectively.
Foliar Fungal Diseases
In many provinces, producers increasingly have access to a wealth of data to inform their in-season IPM strategies for fungal diseases. Localized weather and spore trap data, provided in a timely manner, are informing decision making on the timing of fungicide application, the choice of product, and whether the grower needs to spray at all. Nonetheless, with aggressive diseases such as late blight, we must never be complacent. Just because no spores were detected in your area does not mean there is no potential inoculum lurking around, be it from a seed-borne source, a cull pile, or someone’s home garden. If the weather is conducive to late blight infection, be diligent in your prevention program. Conversely, if it’s hot and dry and there is no evidence of late blight spores, there is ample justification to space out your fungicide schedule. For early blight and brown spot, the recommendation is to ensure good coverage of the lower leaves prior to row closure, before the second and larger spike of Alternaria spores is detected. Ensure rotation of chemistry, as reliance on one product is a recipe for building resistance.
I hope all Canadian potato growers have a great growing season, with timely rains and lots of sunshine. I hope that you also get a chance to enjoy time with family and friends this summer, as we await the results of another season’s promise to be realized. Have a great summer!
