Water Science and Engineering 2008, 1(2) 112-120  DOI:   10.3882/j.issn.1674-2370.2008.02.011   ISSN: 1674-2370 CN: 32-1785/TV

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crop evapotranspiration
pan evaporation
unheated greenhouse
Xu Junzeng
Peng Shizhang
Luo Yufeng
Jiao Xiyun
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Tomato and cowpea crop evapotranspiration in an unheated greenhouse

Xu Junzeng1, Peng Shizhang*1,2, Luo Yufeng1, Jiao Xiyun1

1. State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, College of Water Resources and Environment, Hohai University, Nanjing 210098, P. R. China
2. Institute of Water-Saving Irrigation, Hohai University, Nanjing 210098, P. R. China


With the development of protected cultivation of vegetables in China, it is necessary to study the water requirements of crops in greenhouses. Lysimeter experiments were carried out to investigate tomato (2001) and cowpea (2004) crop evapotranspiration (ETc) in an unheated greenhouse in Eastern China. Results showed remarkably reduced crop evapotranspiration inside the greenhouse as compared with that outside. ETc increased with the growth of the crops, and varied in accordance with the temperature inside the greenhouse and 20-cm pan evaporation outside, reaching its maximum value at the stage when plants’ growth was most active. Differences between the variation of crop evapotranspiration and pan evaporation inside the greenhouse were caused by shading of the pan in the later period when the crops were taller than the location where the pan was installed, 70 cm above ground. The ratio of crop evapotranspiration to pan evaporation was not constant as reported in previous studies, and the variation of the inside ratio αin lagged behind that of the outside ratio αout. Simulation of crop evapotranspiration based on 20-cm pan evaporation inside the greenhouse is more reasonable than that based on 20-cm pan evaporation outside, although pan evaporation outside is more consistent with ETc than that inside. The value of αin, calculated based on air temperature, relative humidity, and ground temperature inside, plays a dominant role in the calculation of ETc. As the crop height increases, altering the location of the inside pan and placing it above the canopy, out of the shade, would help to achieve more reasonable values of crop evapotranspiration.

Keywords crop evapotranspiration   pan evaporation   unheated greenhouse   tomato   cowpea  
Received 2008-01-17 Revised 2008-05-07 Online:  
DOI: 10.3882/j.issn.1674-2370.2008.02.011
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