Abstract
The solar greenhouse is a common protected structure for crop production when ambient temperatures are low. In the North China Plain (NCP) winter temperatures are very low and an improved solar greenhouse with a lowered soil surface (0.5–1.5 m deep), referred to as a sunken solar greenhouse (SSG), is used. A four-season experiment was conducted in a commercial SSG with tomato crops to characterize internal microclimate, sap flow (SF) and crop coefficients. Results show that temperature inside the SSG could be more than 20 °C higher than outside in winter, which favors tomato growth and resulted in acceptable yields. Daily total SF was related to solar radiation, vapor pressure deficit (VPD) and temperature, in that order, both in winter and summer. The decoupling coefficient (which is the ratio of radiative to aerodynamic influences on evapotranspiration) in daytime was 0.76 in winter and 0.84 in summer, indicating strong decoupling (i.e., predominance of radiative influences) of the internal environment where wind speed was low. Basal crop coefficients at the mid stage of crop growth averaged 1.15–1.43 in winter and 0.91–0.92 in spring and summer. Thus, in the SSG, for similar climatic conditions sap flow in winter was higher than that in summer, which should be considered in irrigation scheduling.
Highlights
Received: 17 December 2021Greenhouses are widely used to cultivate offseason cash crops in order to obtain higher yields than in open cropping systems [1,2,3]
2019SU season, extremely high temperatures stopped irrigationinfluenced and finished seasonso inthe order to prepare the following winter inside negatively cropthe growth, farmer abortedfor the crop, i.e., stopped season, which resulted in the lowest irrigation amount
We found that the shapes of the daily curves of sap flow followed those of the inside microclimate (Figure 3)
Summary
Received: 17 December 2021Greenhouses are widely used to cultivate offseason cash crops in order to obtain higher yields than in open cropping systems [1,2,3]. In 2018 it was 196.4 million hectares, 2.4 times that in 2008 [4] Vegetable production in these greenhouses accounted for approximately 30% of China’s total vegetable production [4]. There, vegetable production in greenhouses is popular due to the low winter temperatures [5,6]. An improved solar greenhouse was introduced there, with a soil surface 0.5–1.5 m lower than the outside surface, which increases inside air and soil temperatures and improves crop growth in winter [7]. This greenhouse is referred to as a sunken solar greenhouse (SSG). Because the SSG does not need extra heating and is maintained the same way as a traditional solar greenhouse, SSG popularity has been increasing in NCP
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