Limed ground is the wrong ground for the next potato crop
Limed ground is the wrong ground for the next potato crop, because common scab worsens as soil pH rises and lime raises it.
Promising A person has checked it against its sources. If you skip this, it still grows, just less well. The planner suggests it.
How it works
Common scab (Streptomyces scabies) infects young tubers through the lenticels and is favored as soil goes less acid; at about pH 5.2 and below it is largely suppressed. Lime raises pH and its effect lasts years, so ground limed for a crop that wants sweet soil carries a scab-prone pH into the seasons that follow.
What to do about it
This ground has been limed, and potatoes want it sour. Scab is skin-deep and the tubers still eat, but where it has been a problem, put the potatoes on ground you have not limed, choose a scab-resistant variety, keep the soil evenly moist for the four to nine weeks after planting while the tubers set, and never lime or add wood ash where potatoes are going next. A later pH reading at or below about 5.2 on this ground would quiet this. We will not give a sulfur rate to get there, because the amount is your lab's to give: ask it for its sulfur recommendation for your soil.
The evidence
Evidence: checked against 5 sources in the research-based literature.
The 5 sources
Common scab is controlled or greatly suppressed at soil pH levels of 5.2 or lower
Scab tends not to develop when the soil pH is less than 5.2
Lime will also raise the pH of soil. A soil test will tell you how much lime to add.
Plants it applies to · 1
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How this rule has changed
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Milpa Gardens. “Limed ground is the wrong ground for the next potato crop, because common scab worsens as soil pH rises and lime raises it.” Evidence grade: Promising. https://milpa.garden/rules/limed-ground-wrong-ground-next-potato-crop/
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