Abstract:

The aim is to identify the optimum temperature indicators during sowing period of waxy foxtail millet that are consistent with production and meteorological forecast services. Using daily air temperature and 5 cm soil temperature data from national meteorological observation stations in core planting areas (Huangping, Shibing, Zhenyuan) from 2015-2024, the paper calculated the first occurrence dates of 12℃, 13℃, 14℃ and 15℃ thresholds using a 5-day moving average and curve method. The relationship between air temperature and shallow soil temperature was analyzed using absolute difference and correlation coefficient methods. The stability of the differences between these thresholds and the first occurrence of 5 cm soil temperature ≥15℃ was assessed using coefficient of variation (CV), and the optimum air temperature indicator for sowing was selected based on minimum standard deviation and CV instead of the soil temperature indicator in production. The results showed that, in the core planting area of southeastern Guizhou, daily average 5 cm soil temperature showed a significant positive correlation with air temperature, with the strongest influence from daily average air temperature; the optimum sowing time varied annually: spring temperature warmed up early, sowing could be carried out at the end of March or the beginning of April, in years when late spring cold snaps were severe, sowing could only be done in late April; the differences between 5 cm soil temperature ≥15℃ and air temperature ≥13℃ had the smallest average and standard deviation; the CV of differences between thresholds and soil temperature ≥15℃ ranged from -2.528 to 1.713. In a word, based on the closest timing and highest stability between soil and air temperature indicators, the average air temperature ≥13℃ is recommended as the optimum temperature indicator during sowing of waxy foxtail millet in southeastern Guizhou. This approach enhances the scientific rationality of planting and effectively mitigates low-temperature risks at seedling-stage.

Key words: waxy foxtail millet, sowing indicator, air temperature, soil temperature, southeastern Guizhou