Global: Soil Above 24°C Can Trigger Second Growth; Hot Texas Site Yielded 67% Less
Hot spells during tuber bulking cut dry matter and seed quality, not just tuber shape — field data quantify the penalty of heat at critical growth stages.
Second growth — knobs, chain tubers and malformed daughter tubers — can begin at soil temperatures as low as 24°C during tuber bulking and becomes consistent at a sustained 28–32°C, according to NDSU Extension, with severe cases slashing marketable yield.
In a 2024 Texas A&M study, the hotter Springlake site averaged 67% lower total yield than the Dalhart site, demonstrating how sustained soil heat during bulking compromises the entire crop, not only tuber appearance.
Heat at bulking reduces dry matter accumulation and degrades seed quality for the following season: tubers from heat-stressed crops show weaker vigor, uneven emergence and higher susceptibility to secondary growth in the next generation.
Agronomists recommend several mitigations: maintaining soil moisture through the bulking window to buffer soil temperature, using earlier-maturing varieties in heat-prone regions, and using irrigation to cool the soil without overwatering, which promotes lenticel infections.
With climate trends lengthening hot spells in many potato regions, variety screening for heat tolerance is moving up breeding priorities. Programs in North America and Europe now routinely score advanced lines for performance under elevated soil temperature, alongside traditional yield and disease criteria.
Sources: Gautam et al., Frontiers in Plant Science, 2024; NDSU Extension A1987, Potato Tuber Second Growth; Spud Smart, 2021
