Abstract:

Based on the daily minimum temperature data in the 56 national meteorological stations of Liaoning from 1961 to 2020, frost days and the first frost date were identified using a threshold of ≤0.5℃, then the number of autumn frost days during the peanut growing season and the number of frost days during the maturation stage were calculated. This study analyzed the spatiotemporal characteristics of the first frost date and the number of autumn frost days during the peanut growing season, screened the high−frequency periods and susceptible stations of frost during the peanut maturation period, providing references for frost forecasting and prevention in peanut‒producing areas at middle and high latitudes. The results showed that from 1961 to 2020, the first frost date in 56 stations of Liaoning was from September 8 to November 27, and the first frost date with an 80% guarantee rate was concentrated from late September to mid−October in 92.9% of stations. The first frost dates occurred sequentially in the northeast producing region, the eastern mountainous region, the western producing region, the middle producing area and the southern producing region. Provincial first frost date showed a delayed trend from 1961 to 2020 (1.25d·10y⁻¹, P<0.05), whereas a non−significant advancing change during 2011 to 2020 (−2.24d·10y⁻¹, P=0.53). From 1961 to 2020, the number of autumn frost days during the peanut growing season in 56 stations ranged from 0 to 6d·y⁻¹. In 67.9% of the stations, the number of autumn frost days during the peanut growing season showed a decreasing change (−0.84 to −0.01d·10y⁻¹), with 35.7% of the stations passing the significance test. No autumnal frost events were recorded during the peanut growing season at the stations along the southern coast. However, some stations in the western producing region, northeastern producing region, middle producing region and eastern mountainous region experienced frost during the peanut ripening period in early to mid−September. With the exception of the southern production area, other peanut−producing areas and mountainous areas in eastern Liaoning should prioritize frost prevention during the harvest drying phase from late September to October. In addition, some stations in the aforementioned areas needed to take precautions against frost during the maturation stage in early to mid−September. Although the limiting effect of autumn thermal conditions represented by frost on the late growth stage of peanuts in Liaoning had been alleviating, attention should be paid to the risks of autumn frost during the growing season and frost during the maturation period due to the unstable advancement of the first frost date in recent years when conducting peanut cultivation or expanding planting areas. For the meteorological departments, a 7d dynamic forecast of peanut autumn frost could be initiated in early September to provide reference for planters to harvest at a appropriate time.

Key words: Peanut, Frost damage, First frost date, Liaoning