Limiting factor of dew formation changes seasonally in a semiarid crop field of northwest China

Understanding how seasonal and annual variations in dew formation are controlled by environmental elements of a crop field is necessary for utilizing dew as a water resource for agricultural production. Radiative cooling intensity, wind speed, and water vapor pressure are the key environmental elements for the dew formation. However, a detailed investigation of how seasonal and annual variations in these environmental elements affect the variation in dew formation is unexplored. We examined the relationship between dew characteristics (frequency, amount, and duration) and environmental elements of a semiarid crop field during the cultivation period of corn (April–September) for three years. In spring (April–June), though large nighttime negative net radiation, which indicates strong radiative cooling intensity, was observed, dew rarely occurred and only in small amounts. Conversely, in summer (July–September), dew frequently occurred and in larger amounts despite the lower radiative cooling intensity. In spring, lower water vapor pressure was observed, and thus dew formation was limited by the lack of water source of dew. In summer, water vapor pressure was high, and dew formation was predominantly limited by the radiative cooling intensity. The dew amount during the cultivation period accounted for 5.4% of the rainfall amount on average over the 3 years. However, dew occurred more frequently than rainfall at 53% of the days comprising the cultivation period. Additionally, the occurrence of dew wet the leaves for approximately 10 h indicating the significant impact of leaf wetting by dew on plant eco-physiological functions. The results of this study should advance the understanding of how dew formation is controlled by variations in the environmental elements of a semiarid crop field, which will contribute to improving the utilization of dew as a water resource for agricultural production.