Temporal and Spatial Variation Characteristics of Soil Temperature in Cotton Fields under Different Cropping Systems

Objective] Soil temperature affects the biochemical processes of crops; therefore, elucidating its spatial and temporal distribution characteristics in different cropping systems is an essential part of understanding how to boost cotton yield potential. Method] In 2016 and 2017, continuous, real-time soil temperature monitoring was conducted at a depth of 10-110 cm in three cropping systems, including monoculture cotton (MC), wheat/intercropped cotton (WIC), and wheat/direct-seeded cotton (WDC). We investigated the growth process and various agronomic traits. Result] Different cotton soil temperatures were found between MC and doubled in late May, indicating about 1-3 ℃ higher in the former during the symbiotic period. In early July, the cotton soil temperature of the double-cropping systems at 10-40 cm was higher than that of the MC, but showed the opposite at 40-110 cm. In early August, the differences in soil temperature reduced among the three cropping systems, while the soil temperature of the MC was still slightly lower than that of the double-cropping systems. After mid-September, the soil temperature of the double-cropping systems was lower than that of the MC. The soil temperature mainly influenced the duration of cotton seedling to squaring, and flowering to the boll-opening period. At the same time, there was a subtle effect on the squaring to flowering and boll period. In general, higher average soil temperatures were associated with shorter growth period durations. During the same period, the lowest daily soil temperature of the double-cropping systems occurred about one hour earlier than in the MC; however, the highest daily temperature appeared at the same time. There was a linear relationship between accumulated soil temperature and biomass at different layers across cropping systems. Conclusion] Controlling the timing and quantity of irrigation water can assist agronomic practices by alleviating the effect of soil temperature on cotton growth. Increased accumulative soil temperature is beneficial to cotton emergence and boll opening in double-cropping systems. This study provides a theoretical basis for rational allocation and management of different cropping systems.