In cool climates, low temperature is critical for growth and yield of sweet potato (Ipomoea batatas L.). Despite its negative effects, few studies have quantified the impact. We evaluated effects of soil temperature (T_s) on growth and yield in sweet potato from 2-year field trials in northern Japan. T_s was controlled by three steps using plastic mulch at different colors (green, black and white) with different T_s ranged in 21~24°C especially at early growth before the surface of the mulch covered by plant canopy. Higher T_s significantly increased vine elongation, branching, and leaf appearance, and the magnitude of increased by higher T_s decreased with proceeding growth stages. Increasing T_s significantly increased leaf chlorophyll content and stomatal conductance. Across treatments and years, aboveground biomass was linearly and positively correlated with T_s, and 58 g m^-2 increased in aboveground biomass was observed per 1°C increase in T_s. However, final storage root fresh yield was not significantly affected by high T_s over years. Increased individual storage root weight at high T_s was offset by decreased storage root number. The present quantitative study tested in northern Japan showed that, the enhanced aboveground growth in sweet potato at higher T_s especially during early growth did not contribute to increase of storage root yields in cool climates.

中文翻译：

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凉爽气候下土壤温度对甘薯生长和产量的影响

在凉爽的气候中，低温对于甘薯（Ipomoea batatas L.）的生长和产量至关重要。尽管有负面影响，但很少有研究量化影响。我们从日本北部进行了2年的田间试验，评估了土壤温度（T _s）对甘薯生长和产量的影响。用不同颜色（绿色，黑色和白色）的塑料覆盖物通过三个步骤控制T _s，不同的T _s范围为21〜24°C，尤其是在覆盖植物冠层覆盖的覆盖物表面早期生长的早期。更高Ť _š显著增加藤伸长率，支化，和叶的外观，并且增加了较高量级Ť_s随着成长阶段_的增加而减少。增加牛逼_小号显著增加叶绿素含量和气孔导度。在所有处理和多年中，地上生物量与T _s呈线性正相关，并且每1°C T _s地上生物量增加58 gm ^-2。然而，最终的存储根鲜产量无显著高影响牛逼_小号多年来。高T _s时增加单独的贮藏根重被减少的存储根号所抵消。目前在日本北部进行的定量研究表明，在较高的T _{s条件下，}甘薯地上生长的增强，特别是在早期生长期间，并没有促进凉爽气候下贮藏根的产量。